Babylon.js/src/Engines/engine.ts

import { Observer, Observable } from "../Misc/observable";
import { PerformanceMonitor } from "../Misc/performanceMonitor";
import { StringDictionary } from "../Misc/stringDictionary";
import { PromisePolyfill } from "../Misc/promise";
import { Tools, ICustomAnimationFrameRequester, PerfCounter, IFileRequest } from "../Misc/tools";
import { Nullable, FloatArray, DataArray, IndicesArray } from "../types";
import { Camera } from "../Cameras/camera";
import { Scene } from "../scene";
import { Matrix, Color3, Color4, Viewport, Size, Vector4 } from "../Maths/math";
import { Scalar } from "../Maths/math.scalar";
import { IDisplayChangedEventArgs } from "../Engines/engine";
import { VertexBuffer } from "../Meshes/buffer";
import { UniformBuffer } from "../Materials/uniformBuffer";
import { Effect, EffectCreationOptions, EffectFallbacks } from "../Materials/effect";
import { Material } from "../Materials/material";
import { IInternalTextureTracker, DummyInternalTextureTracker } from "../Materials/Textures/internalTextureTracker";
import { IInternalTextureLoader } from "../Materials/Textures/internalTextureLoader";
import { InternalTexture } from "../Materials/Textures/internalTexture";
import { BaseTexture } from "../Materials/Textures/baseTexture";
import { IMultiRenderTargetOptions } from "../Materials/Textures/multiRenderTarget";
import { _TimeToken } from "../Instrumentation/timeToken";
import { IAudioEngine } from "../Audio/audioEngine";
import { IOfflineProvider } from "../Offline/IOfflineProvider";
import { ILoadingScreen } from "../Loading/loadingScreen";
import { _DepthCullingState, _StencilState, _AlphaState } from "../States/index";
import { Constants } from "./constants";
import { DomManagement } from "../Misc/domManagement";
import { Logger } from "../Misc/logger";
import { EngineStore } from "./engineStore";
import { RenderTargetCreationOptions } from "../Materials/Textures/renderTargetCreationOptions";
import { _DevTools } from '../Misc/devTools';
import { WebRequest } from '../Misc/webRequest';

declare type PostProcess = import("../PostProcesses/postProcess").PostProcess;
declare type Texture = import("../Materials/Textures/texture").Texture;
declare type VideoTexture = import("../Materials/Textures/videoTexture").VideoTexture;
declare type RenderTargetTexture = import("../Materials/Textures/renderTargetTexture").RenderTargetTexture;

/**
 * Keeps track of all the buffer info used in engine.
 */
class BufferPointer {
    public active: boolean;
    public index: number;
    public size: number;
    public type: number;
    public normalized: boolean;
    public stride: number;
    public offset: number;
    public buffer: WebGLBuffer;
}

/**
 * Interface for attribute information associated with buffer instanciation
 */
export class InstancingAttributeInfo {
    /**
     * Index/offset of the attribute in the vertex shader
     */
    index: number;

    /**
     * size of the attribute, 1, 2, 3 or 4
     */
    attributeSize: number;

    /**
     * type of the attribute, gl.BYTE, gl.UNSIGNED_BYTE, gl.SHORT, gl.UNSIGNED_SHORT, gl.FIXED, gl.FLOAT.
     * default is FLOAT
     */
    attribyteType: number;

    /**
     * normalization of fixed-point data. behavior unclear, use FALSE, default is FALSE
     */
    normalized: boolean;

    /**
     * Offset of the data in the Vertex Buffer acting as the instancing buffer
     */
    offset: number;

    /**
     * Name of the GLSL attribute, for debugging purpose only
     */
    attributeName: string;
}

/**
 * Define options used to create a depth texture
 */
export class DepthTextureCreationOptions {
    /** Specifies whether or not a stencil should be allocated in the texture */
    generateStencil?: boolean;
    /** Specifies whether or not bilinear filtering is enable on the texture */
    bilinearFiltering?: boolean;
    /** Specifies the comparison function to set on the texture. If 0 or undefined, the texture is not in comparison mode */
    comparisonFunction?: number;
    /** Specifies if the created texture is a cube texture */
    isCube?: boolean;
}

/**
 * Class used to describe the capabilities of the engine relatively to the current browser
 */
export class EngineCapabilities {
    /** Maximum textures units per fragment shader */
    public maxTexturesImageUnits: number;
    /** Maximum texture units per vertex shader */
    public maxVertexTextureImageUnits: number;
    /** Maximum textures units in the entire pipeline */
    public maxCombinedTexturesImageUnits: number;
    /** Maximum texture size */
    public maxTextureSize: number;
    /** Maximum cube texture size */
    public maxCubemapTextureSize: number;
    /** Maximum render texture size */
    public maxRenderTextureSize: number;
    /** Maximum number of vertex attributes */
    public maxVertexAttribs: number;
    /** Maximum number of varyings */
    public maxVaryingVectors: number;
    /** Maximum number of uniforms per vertex shader */
    public maxVertexUniformVectors: number;
    /** Maximum number of uniforms per fragment shader */
    public maxFragmentUniformVectors: number;
    /** Defines if standard derivates (dx/dy) are supported */
    public standardDerivatives: boolean;
    /** Defines if s3tc texture compression is supported */
    public s3tc: Nullable<WEBGL_compressed_texture_s3tc>;
    /** Defines if pvrtc texture compression is supported */
    public pvrtc: any; //WEBGL_compressed_texture_pvrtc;
    /** Defines if etc1 texture compression is supported */
    public etc1: any; //WEBGL_compressed_texture_etc1;
    /** Defines if etc2 texture compression is supported */
    public etc2: any; //WEBGL_compressed_texture_etc;
    /** Defines if astc texture compression is supported */
    public astc: any; //WEBGL_compressed_texture_astc;
    /** Defines if float textures are supported */
    public textureFloat: boolean;
    /** Defines if vertex array objects are supported */
    public vertexArrayObject: boolean;
    /** Gets the webgl extension for anisotropic filtering (null if not supported) */
    public textureAnisotropicFilterExtension: Nullable<EXT_texture_filter_anisotropic>;
    /** Gets the maximum level of anisotropy supported */
    public maxAnisotropy: number;
    /** Defines if instancing is supported */
    public instancedArrays: boolean;
    /** Defines if 32 bits indices are supported */
    public uintIndices: boolean;
    /** Defines if high precision shaders are supported */
    public highPrecisionShaderSupported: boolean;
    /** Defines if depth reading in the fragment shader is supported */
    public fragmentDepthSupported: boolean;
    /** Defines if float texture linear filtering is supported*/
    public textureFloatLinearFiltering: boolean;
    /** Defines if rendering to float textures is supported */
    public textureFloatRender: boolean;
    /** Defines if half float textures are supported*/
    public textureHalfFloat: boolean;
    /** Defines if half float texture linear filtering is supported*/
    public textureHalfFloatLinearFiltering: boolean;
    /** Defines if rendering to half float textures is supported */
    public textureHalfFloatRender: boolean;
    /** Defines if textureLOD shader command is supported */
    public textureLOD: boolean;
    /** Defines if draw buffers extension is supported */
    public drawBuffersExtension: boolean;
    /** Defines if depth textures are supported */
    public depthTextureExtension: boolean;
    /** Defines if float color buffer are supported */
    public colorBufferFloat: boolean;
    /** Gets disjoint timer query extension (null if not supported) */
    public timerQuery: EXT_disjoint_timer_query;
    /** Defines if timestamp can be used with timer query */
    public canUseTimestampForTimerQuery: boolean;
    /** Function used to let the system compiles shaders in background */
    public parallelShaderCompile: {
        COMPLETION_STATUS_KHR: number;
    };
}

/** Interface defining initialization parameters for Engine class */
export interface EngineOptions extends WebGLContextAttributes {
    /**
     * Defines if the engine should no exceed a specified device ratio
     * @see https://developer.mozilla.org/en-US/docs/Web/API/Window/devicePixelRatio
     */
    limitDeviceRatio?: number;
    /**
     * Defines if webvr should be enabled automatically
     * @see http://doc.babylonjs.com/how_to/webvr_camera
     */
    autoEnableWebVR?: boolean;
    /**
     * Defines if webgl2 should be turned off even if supported
     * @see http://doc.babylonjs.com/features/webgl2
     */
    disableWebGL2Support?: boolean;
    /**
     * Defines if webaudio should be initialized as well
     * @see http://doc.babylonjs.com/how_to/playing_sounds_and_music
     */
    audioEngine?: boolean;
    /**
     * Defines if animations should run using a deterministic lock step
     * @see http://doc.babylonjs.com/babylon101/animations#deterministic-lockstep
     */
    deterministicLockstep?: boolean;
    /** Defines the maximum steps to use with deterministic lock step mode */
    lockstepMaxSteps?: number;
    /**
     * Defines that engine should ignore context lost events
     * If this event happens when this parameter is true, you will have to reload the page to restore rendering
     */
    doNotHandleContextLost?: boolean;
    /**
     * Defines that engine should ignore modifying touch action attribute and style
     * If not handle, you might need to set it up on your side for expected touch devices behavior.
     */
    doNotHandleTouchAction?: boolean;
    /**
     * Defines that engine should compile shaders with high precision floats (if supported). True by default
     */
    useHighPrecisionFloats?: boolean;
}

/**
 * Defines the interface used by display changed events
 */
export interface IDisplayChangedEventArgs {
    /** Gets the vrDisplay object (if any) */
    vrDisplay: Nullable<any>;
    /** Gets a boolean indicating if webVR is supported */
    vrSupported: boolean;
}

/**
 * The engine class is responsible for interfacing with all lower-level APIs such as WebGL and Audio
 */
export class Engine {
    /** Use this array to turn off some WebGL2 features on known buggy browsers version */
    public static ExceptionList = [
        { key: "Chrome/63.0", capture: "63\\.0\\.3239\\.(\\d+)", captureConstraint: 108, targets: ["uniformBuffer"] },
        { key: "Firefox/58", capture: null, captureConstraint: null, targets: ["uniformBuffer"] },
        { key: "Firefox/59", capture: null, captureConstraint: null, targets: ["uniformBuffer"] },
        { key: "Macintosh", capture: null, captureConstraint: null, targets: ["textureBindingOptimization"] },
        { key: "iPhone", capture: null, captureConstraint: null, targets: ["textureBindingOptimization"] },
        { key: "iPad", capture: null, captureConstraint: null, targets: ["textureBindingOptimization"] }
    ];

    /** Gets the list of created engines */
    public static get Instances(): Engine[] {
        return EngineStore.Instances;
    }

    /**
     * Gets the latest created engine
     */
    public static get LastCreatedEngine(): Nullable<Engine> {
        return EngineStore.LastCreatedEngine;
    }

    /**
     * Gets the latest created scene
     */
    public static get LastCreatedScene(): Nullable<Scene> {
        return EngineStore.LastCreatedScene;
    }

    /**
     * Will flag all materials in all scenes in all engines as dirty to trigger new shader compilation
     * @param flag defines which part of the materials must be marked as dirty
     * @param predicate defines a predicate used to filter which materials should be affected
     */
    public static MarkAllMaterialsAsDirty(flag: number, predicate?: (mat: Material) => boolean): void {
        for (var engineIndex = 0; engineIndex < Engine.Instances.length; engineIndex++) {
            var engine = Engine.Instances[engineIndex];

            for (var sceneIndex = 0; sceneIndex < engine.scenes.length; sceneIndex++) {
                engine.scenes[sceneIndex].markAllMaterialsAsDirty(flag, predicate);
            }
        }
    }

    /**
     * Hidden
     */
    public static _TextureLoaders: IInternalTextureLoader[] = [];

    // Const statics
    /** Defines that alpha blending is disabled */
    public static readonly ALPHA_DISABLE = Constants.ALPHA_DISABLE;
    /** Defines that alpha blending to SRC ALPHA * SRC + DEST */
    public static readonly ALPHA_ADD = Constants.ALPHA_ADD;
    /** Defines that alpha blending to SRC ALPHA * SRC + (1 - SRC ALPHA) * DEST */
    public static readonly ALPHA_COMBINE = Constants.ALPHA_COMBINE;
    /** Defines that alpha blending to DEST - SRC * DEST */
    public static readonly ALPHA_SUBTRACT = Constants.ALPHA_SUBTRACT;
    /** Defines that alpha blending to SRC * DEST */
    public static readonly ALPHA_MULTIPLY = Constants.ALPHA_MULTIPLY;
    /** Defines that alpha blending to SRC ALPHA * SRC + (1 - SRC) * DEST */
    public static readonly ALPHA_MAXIMIZED = Constants.ALPHA_MAXIMIZED;
    /** Defines that alpha blending to SRC + DEST */
    public static readonly ALPHA_ONEONE = Constants.ALPHA_ONEONE;
    /** Defines that alpha blending to SRC + (1 - SRC ALPHA) * DEST */
    public static readonly ALPHA_PREMULTIPLIED = Constants.ALPHA_PREMULTIPLIED;
    /**
     * Defines that alpha blending to SRC + (1 - SRC ALPHA) * DEST
     * Alpha will be set to (1 - SRC ALPHA) * DEST ALPHA
     */
    public static readonly ALPHA_PREMULTIPLIED_PORTERDUFF = Constants.ALPHA_PREMULTIPLIED_PORTERDUFF;
    /** Defines that alpha blending to CST * SRC + (1 - CST) * DEST */
    public static readonly ALPHA_INTERPOLATE = Constants.ALPHA_INTERPOLATE;
    /**
     * Defines that alpha blending to SRC + (1 - SRC) * DEST
     * Alpha will be set to SRC ALPHA + (1 - SRC ALPHA) * DEST ALPHA
     */
    public static readonly ALPHA_SCREENMODE = Constants.ALPHA_SCREENMODE;

    /** Defines that the ressource is not delayed*/
    public static readonly DELAYLOADSTATE_NONE = Constants.DELAYLOADSTATE_NONE;
    /** Defines that the ressource was successfully delay loaded */
    public static readonly DELAYLOADSTATE_LOADED = Constants.DELAYLOADSTATE_LOADED;
    /** Defines that the ressource is currently delay loading */
    public static readonly DELAYLOADSTATE_LOADING = Constants.DELAYLOADSTATE_LOADING;
    /** Defines that the ressource is delayed and has not started loading */
    public static readonly DELAYLOADSTATE_NOTLOADED = Constants.DELAYLOADSTATE_NOTLOADED;

    // Depht or Stencil test Constants.
    /** Passed to depthFunction or stencilFunction to specify depth or stencil tests will never pass. i.e. Nothing will be drawn */
    public static readonly NEVER = Constants.NEVER;
    /** Passed to depthFunction or stencilFunction to specify depth or stencil tests will always pass. i.e. Pixels will be drawn in the order they are drawn */
    public static readonly ALWAYS = Constants.ALWAYS;
    /** Passed to depthFunction or stencilFunction to specify depth or stencil tests will pass if the new depth value is less than the stored value */
    public static readonly LESS = Constants.LESS;
    /** Passed to depthFunction or stencilFunction to specify depth or stencil tests will pass if the new depth value is equals to the stored value */
    public static readonly EQUAL = Constants.EQUAL;
    /** Passed to depthFunction or stencilFunction to specify depth or stencil tests will pass if the new depth value is less than or equal to the stored value */
    public static readonly LEQUAL = Constants.LEQUAL;
    /** Passed to depthFunction or stencilFunction to specify depth or stencil tests will pass if the new depth value is greater than the stored value */
    public static readonly GREATER = Constants.GREATER;
    /** Passed to depthFunction or stencilFunction to specify depth or stencil tests will pass if the new depth value is greater than or equal to the stored value */
    public static readonly GEQUAL = Constants.GEQUAL;
    /** Passed to depthFunction or stencilFunction to specify depth or stencil tests will pass if the new depth value is not equal to the stored value */
    public static readonly NOTEQUAL = Constants.NOTEQUAL;

    // Stencil Actions Constants.
    /** Passed to stencilOperation to specify that stencil value must be kept */
    public static readonly KEEP = Constants.KEEP;
    /** Passed to stencilOperation to specify that stencil value must be replaced */
    public static readonly REPLACE = Constants.REPLACE;
    /** Passed to stencilOperation to specify that stencil value must be incremented */
    public static readonly INCR = Constants.INCR;
    /** Passed to stencilOperation to specify that stencil value must be decremented */
    public static readonly DECR = Constants.DECR;
    /** Passed to stencilOperation to specify that stencil value must be inverted */
    public static readonly INVERT = Constants.INVERT;
    /** Passed to stencilOperation to specify that stencil value must be incremented with wrapping */
    public static readonly INCR_WRAP = Constants.INCR_WRAP;
    /** Passed to stencilOperation to specify that stencil value must be decremented with wrapping */
    public static readonly DECR_WRAP = Constants.DECR_WRAP;

    /** Texture is not repeating outside of 0..1 UVs */
    public static readonly TEXTURE_CLAMP_ADDRESSMODE = Constants.TEXTURE_CLAMP_ADDRESSMODE;
    /** Texture is repeating outside of 0..1 UVs */
    public static readonly TEXTURE_WRAP_ADDRESSMODE = Constants.TEXTURE_WRAP_ADDRESSMODE;
    /** Texture is repeating and mirrored */
    public static readonly TEXTURE_MIRROR_ADDRESSMODE = Constants.TEXTURE_MIRROR_ADDRESSMODE;

    /** ALPHA */
    public static readonly TEXTUREFORMAT_ALPHA = Constants.TEXTUREFORMAT_ALPHA;
    /** LUMINANCE */
    public static readonly TEXTUREFORMAT_LUMINANCE = Constants.TEXTUREFORMAT_LUMINANCE;
    /** LUMINANCE_ALPHA */
    public static readonly TEXTUREFORMAT_LUMINANCE_ALPHA = Constants.TEXTUREFORMAT_LUMINANCE_ALPHA;
    /** RGB */
    public static readonly TEXTUREFORMAT_RGB = Constants.TEXTUREFORMAT_RGB;
    /** RGBA */
    public static readonly TEXTUREFORMAT_RGBA = Constants.TEXTUREFORMAT_RGBA;
    /** RED */
    public static readonly TEXTUREFORMAT_RED = Constants.TEXTUREFORMAT_RED;
    /** RED (2nd reference) */
    public static readonly TEXTUREFORMAT_R = Constants.TEXTUREFORMAT_R;
    /** RG */
    public static readonly TEXTUREFORMAT_RG = Constants.TEXTUREFORMAT_RG;
    /** RED_INTEGER */
    public static readonly TEXTUREFORMAT_RED_INTEGER = Constants.TEXTUREFORMAT_RED_INTEGER;
    /** RED_INTEGER (2nd reference) */
    public static readonly TEXTUREFORMAT_R_INTEGER = Constants.TEXTUREFORMAT_R_INTEGER;
    /** RG_INTEGER */
    public static readonly TEXTUREFORMAT_RG_INTEGER = Constants.TEXTUREFORMAT_RG_INTEGER;
    /** RGB_INTEGER */
    public static readonly TEXTUREFORMAT_RGB_INTEGER = Constants.TEXTUREFORMAT_RGB_INTEGER;
    /** RGBA_INTEGER */
    public static readonly TEXTUREFORMAT_RGBA_INTEGER = Constants.TEXTUREFORMAT_RGBA_INTEGER;

    /** UNSIGNED_BYTE */
    public static readonly TEXTURETYPE_UNSIGNED_BYTE = Constants.TEXTURETYPE_UNSIGNED_BYTE;
    /** UNSIGNED_BYTE (2nd reference) */
    public static readonly TEXTURETYPE_UNSIGNED_INT = Constants.TEXTURETYPE_UNSIGNED_INT;
    /** FLOAT */
    public static readonly TEXTURETYPE_FLOAT = Constants.TEXTURETYPE_FLOAT;
    /** HALF_FLOAT */
    public static readonly TEXTURETYPE_HALF_FLOAT = Constants.TEXTURETYPE_HALF_FLOAT;
    /** BYTE */
    public static readonly TEXTURETYPE_BYTE = Constants.TEXTURETYPE_BYTE;
    /** SHORT */
    public static readonly TEXTURETYPE_SHORT = Constants.TEXTURETYPE_SHORT;
    /** UNSIGNED_SHORT */
    public static readonly TEXTURETYPE_UNSIGNED_SHORT = Constants.TEXTURETYPE_UNSIGNED_SHORT;
    /** INT */
    public static readonly TEXTURETYPE_INT = Constants.TEXTURETYPE_INT;
    /** UNSIGNED_INT */
    public static readonly TEXTURETYPE_UNSIGNED_INTEGER = Constants.TEXTURETYPE_UNSIGNED_INTEGER;
    /** UNSIGNED_SHORT_4_4_4_4 */
    public static readonly TEXTURETYPE_UNSIGNED_SHORT_4_4_4_4 = Constants.TEXTURETYPE_UNSIGNED_SHORT_4_4_4_4;
    /** UNSIGNED_SHORT_5_5_5_1 */
    public static readonly TEXTURETYPE_UNSIGNED_SHORT_5_5_5_1 = Constants.TEXTURETYPE_UNSIGNED_SHORT_5_5_5_1;
    /** UNSIGNED_SHORT_5_6_5 */
    public static readonly TEXTURETYPE_UNSIGNED_SHORT_5_6_5 = Constants.TEXTURETYPE_UNSIGNED_SHORT_5_6_5;
    /** UNSIGNED_INT_2_10_10_10_REV */
    public static readonly TEXTURETYPE_UNSIGNED_INT_2_10_10_10_REV = Constants.TEXTURETYPE_UNSIGNED_INT_2_10_10_10_REV;
    /** UNSIGNED_INT_24_8 */
    public static readonly TEXTURETYPE_UNSIGNED_INT_24_8 = Constants.TEXTURETYPE_UNSIGNED_INT_24_8;
    /** UNSIGNED_INT_10F_11F_11F_REV */
    public static readonly TEXTURETYPE_UNSIGNED_INT_10F_11F_11F_REV = Constants.TEXTURETYPE_UNSIGNED_INT_10F_11F_11F_REV;
    /** UNSIGNED_INT_5_9_9_9_REV */
    public static readonly TEXTURETYPE_UNSIGNED_INT_5_9_9_9_REV = Constants.TEXTURETYPE_UNSIGNED_INT_5_9_9_9_REV;
    /** FLOAT_32_UNSIGNED_INT_24_8_REV */
    public static readonly TEXTURETYPE_FLOAT_32_UNSIGNED_INT_24_8_REV = Constants.TEXTURETYPE_FLOAT_32_UNSIGNED_INT_24_8_REV;

    /** nearest is mag = nearest and min = nearest and mip = linear */
    public static readonly TEXTURE_NEAREST_SAMPLINGMODE = Constants.TEXTURE_NEAREST_SAMPLINGMODE;
    /** Bilinear is mag = linear and min = linear and mip = nearest */
    public static readonly TEXTURE_BILINEAR_SAMPLINGMODE = Constants.TEXTURE_BILINEAR_SAMPLINGMODE;
    /** Trilinear is mag = linear and min = linear and mip = linear */
    public static readonly TEXTURE_TRILINEAR_SAMPLINGMODE = Constants.TEXTURE_TRILINEAR_SAMPLINGMODE;
    /** nearest is mag = nearest and min = nearest and mip = linear */
    public static readonly TEXTURE_NEAREST_NEAREST_MIPLINEAR = Constants.TEXTURE_NEAREST_NEAREST_MIPLINEAR;
    /** Bilinear is mag = linear and min = linear and mip = nearest */
    public static readonly TEXTURE_LINEAR_LINEAR_MIPNEAREST = Constants.TEXTURE_LINEAR_LINEAR_MIPNEAREST;
    /** Trilinear is mag = linear and min = linear and mip = linear */
    public static readonly TEXTURE_LINEAR_LINEAR_MIPLINEAR = Constants.TEXTURE_LINEAR_LINEAR_MIPLINEAR;
    /** mag = nearest and min = nearest and mip = nearest */
    public static readonly TEXTURE_NEAREST_NEAREST_MIPNEAREST = Constants.TEXTURE_NEAREST_NEAREST_MIPNEAREST;
    /** mag = nearest and min = linear and mip = nearest */
    public static readonly TEXTURE_NEAREST_LINEAR_MIPNEAREST = Constants.TEXTURE_NEAREST_LINEAR_MIPNEAREST;
    /** mag = nearest and min = linear and mip = linear */
    public static readonly TEXTURE_NEAREST_LINEAR_MIPLINEAR = Constants.TEXTURE_NEAREST_LINEAR_MIPLINEAR;
    /** mag = nearest and min = linear and mip = none */
    public static readonly TEXTURE_NEAREST_LINEAR = Constants.TEXTURE_NEAREST_LINEAR;
    /** mag = nearest and min = nearest and mip = none */
    public static readonly TEXTURE_NEAREST_NEAREST = Constants.TEXTURE_NEAREST_NEAREST;
    /** mag = linear and min = nearest and mip = nearest */
    public static readonly TEXTURE_LINEAR_NEAREST_MIPNEAREST = Constants.TEXTURE_LINEAR_NEAREST_MIPNEAREST;
    /** mag = linear and min = nearest and mip = linear */
    public static readonly TEXTURE_LINEAR_NEAREST_MIPLINEAR = Constants.TEXTURE_LINEAR_NEAREST_MIPLINEAR;
    /** mag = linear and min = linear and mip = none */
    public static readonly TEXTURE_LINEAR_LINEAR = Constants.TEXTURE_LINEAR_LINEAR;
    /** mag = linear and min = nearest and mip = none */
    public static readonly TEXTURE_LINEAR_NEAREST = Constants.TEXTURE_LINEAR_NEAREST;

    /** Explicit coordinates mode */
    public static readonly TEXTURE_EXPLICIT_MODE = Constants.TEXTURE_EXPLICIT_MODE;
    /** Spherical coordinates mode */
    public static readonly TEXTURE_SPHERICAL_MODE = Constants.TEXTURE_SPHERICAL_MODE;
    /** Planar coordinates mode */
    public static readonly TEXTURE_PLANAR_MODE = Constants.TEXTURE_PLANAR_MODE;
    /** Cubic coordinates mode */
    public static readonly TEXTURE_CUBIC_MODE = Constants.TEXTURE_CUBIC_MODE;
    /** Projection coordinates mode */
    public static readonly TEXTURE_PROJECTION_MODE = Constants.TEXTURE_PROJECTION_MODE;
    /** Skybox coordinates mode */
    public static readonly TEXTURE_SKYBOX_MODE = Constants.TEXTURE_SKYBOX_MODE;
    /** Inverse Cubic coordinates mode */
    public static readonly TEXTURE_INVCUBIC_MODE = Constants.TEXTURE_INVCUBIC_MODE;
    /** Equirectangular coordinates mode */
    public static readonly TEXTURE_EQUIRECTANGULAR_MODE = Constants.TEXTURE_EQUIRECTANGULAR_MODE;
    /** Equirectangular Fixed coordinates mode */
    public static readonly TEXTURE_FIXED_EQUIRECTANGULAR_MODE = Constants.TEXTURE_FIXED_EQUIRECTANGULAR_MODE;
    /** Equirectangular Fixed Mirrored coordinates mode */
    public static readonly TEXTURE_FIXED_EQUIRECTANGULAR_MIRRORED_MODE = Constants.TEXTURE_FIXED_EQUIRECTANGULAR_MIRRORED_MODE;

    // Texture rescaling mode
    /** Defines that texture rescaling will use a floor to find the closer power of 2 size */
    public static readonly SCALEMODE_FLOOR = Constants.SCALEMODE_FLOOR;
    /** Defines that texture rescaling will look for the nearest power of 2 size */
    public static readonly SCALEMODE_NEAREST = Constants.SCALEMODE_NEAREST;
    /** Defines that texture rescaling will use a ceil to find the closer power of 2 size */
    public static readonly SCALEMODE_CEILING = Constants.SCALEMODE_CEILING;

    /**
     * Returns the current npm package of the sdk
     */
    // Not mixed with Version for tooling purpose.
    public static get NpmPackage(): string {
        return "babylonjs@4.0.0-alpha.29";
    }

    /**
     * Returns the current version of the framework
     */
    public static get Version(): string {
        return "4.0.0-alpha.29";
    }

    /**
     * Returns a string describing the current engine
     */
    public get description(): string {
        let description = "WebGL" + this.webGLVersion;

        if (this._caps.parallelShaderCompile) {
            description += " - Parallel shader compilation";
        }

        return description;
    }

    // Updatable statics so stick with vars here

    /**
     * Gets or sets the epsilon value used by collision engine
     */
    public static CollisionsEpsilon = 0.001;

    /**
     * Gets or sets the relative url used to load shaders if using the engine in non-minified mode
     */
    public static get ShadersRepository(): string {
        return Effect.ShadersRepository;
    }
    public static set ShadersRepository(value: string) {
        Effect.ShadersRepository = value;
    }

    /**
     * Method called to create the default loading screen.
     * This can be overriden in your own app.
     * @param canvas The rendering canvas element
     * @returns The loading screen
     */
    public static DefaultLoadingScreenFactory(canvas: HTMLCanvasElement): ILoadingScreen {
        throw _DevTools.WarnImport("LoadingScreen");
    }

    /**
     * Method called to create the default rescale post process on each engine.
     */
    public static _RescalePostProcessFactory: Nullable<(engine: Engine) => PostProcess> = null;

    // Public members

    /**
     * Gets or sets a boolean that indicates if textures must be forced to power of 2 size even if not required
     */
    public forcePOTTextures = false;

    /**
     * Gets a boolean indicating if the engine is currently rendering in fullscreen mode
     */
    public isFullscreen = false;

    /**
     * Gets a boolean indicating if the pointer is currently locked
     */
    public isPointerLock = false;

    /**
     * Gets or sets a boolean indicating if back faces must be culled (true by default)
     */
    public cullBackFaces = true;

    /**
     * Gets or sets a boolean indicating if the engine must keep rendering even if the window is not in foregroun
     */
    public renderEvenInBackground = true;

    /**
     * Gets or sets a boolean indicating that cache can be kept between frames
     */
    public preventCacheWipeBetweenFrames = false;

    /**
     * Gets or sets a boolean to enable/disable IndexedDB support and avoid XHR on .manifest
     **/
    public enableOfflineSupport = false;

    /**
     * Gets or sets a boolean to enable/disable checking manifest if IndexedDB support is enabled (js will always consider the database is up to date)
     **/
    public disableManifestCheck = false;

    /**
     * Gets the list of created scenes
     */
    public scenes = new Array<Scene>();

    /**
     * Event raised when a new scene is created
     */
    public onNewSceneAddedObservable = new Observable<Scene>();

    /**
     * Gets the list of created postprocesses
     */
    public postProcesses = new Array<PostProcess>();

    /** Gets or sets a boolean indicating if the engine should validate programs after compilation */
    public validateShaderPrograms = false;

    // Observables

    /**
     * Observable event triggered each time the rendering canvas is resized
     */
    public onResizeObservable = new Observable<Engine>();

    /**
     * Observable event triggered each time the canvas loses focus
     */
    public onCanvasBlurObservable = new Observable<Engine>();

    /**
     * Observable event triggered each time the canvas gains focus
     */
    public onCanvasFocusObservable = new Observable<Engine>();

    /**
     * Observable event triggered each time the canvas receives pointerout event
     */
    public onCanvasPointerOutObservable = new Observable<PointerEvent>();

    /**
     * Observable event triggered before each texture is initialized
     */
    public onBeforeTextureInitObservable = new Observable<Texture>();

    //WebVR

    private _vrDisplay: any = undefined;
    private _vrSupported: boolean = false;
    private _oldSize: Size;
    private _oldHardwareScaleFactor: number;
    private _vrExclusivePointerMode = false;
    private _webVRInitPromise: Promise<IDisplayChangedEventArgs>;

    /**
     * Gets a boolean indicating that the engine is currently in VR exclusive mode for the pointers
     * @see https://docs.microsoft.com/en-us/microsoft-edge/webvr/essentials#mouse-input
     */
    public get isInVRExclusivePointerMode(): boolean {
        return this._vrExclusivePointerMode;
    }

    // Uniform buffers list

    /**
     * Gets or sets a boolean indicating that uniform buffers must be disabled even if they are supported
     */
    public disableUniformBuffers = false;

    /** @hidden */
    public _uniformBuffers = new Array<UniformBuffer>();

    /**
     * Gets a boolean indicating that the engine supports uniform buffers
     * @see http://doc.babylonjs.com/features/webgl2#uniform-buffer-objets
     */
    public get supportsUniformBuffers(): boolean {
        return this.webGLVersion > 1 && !this.disableUniformBuffers;
    }

    // Observables

    /**
     * Observable raised when the engine begins a new frame
     */
    public onBeginFrameObservable = new Observable<Engine>();

    /**
     * If set, will be used to request the next animation frame for the render loop
     */
    public customAnimationFrameRequester: Nullable<ICustomAnimationFrameRequester> = null;

    /**
     * Observable raised when the engine ends the current frame
     */
    public onEndFrameObservable = new Observable<Engine>();

    /**
     * Observable raised when the engine is about to compile a shader
     */
    public onBeforeShaderCompilationObservable = new Observable<Engine>();

    /**
     * Observable raised when the engine has jsut compiled a shader
     */
    public onAfterShaderCompilationObservable = new Observable<Engine>();

    // Private Members

    /** @hidden */
    public _gl: WebGLRenderingContext;
    private _renderingCanvas: Nullable<HTMLCanvasElement>;
    private _windowIsBackground = false;
    private _webGLVersion = 1.0;

    protected _highPrecisionShadersAllowed = true;
    /** @hidden */
    public get _shouldUseHighPrecisionShader(): boolean {
        return this._caps.highPrecisionShaderSupported && this._highPrecisionShadersAllowed;
    }

    /**
     * Gets a boolean indicating that only power of 2 textures are supported
     * Please note that you can still use non power of 2 textures but in this case the engine will forcefully convert them
     */
    public get needPOTTextures(): boolean {
        return this._webGLVersion < 2 || this.forcePOTTextures;
    }

    /** @hidden */
    public _badOS = false;

    /** @hidden */
    public _badDesktopOS = false;

    /**
     * Gets or sets a value indicating if we want to disable texture binding optimization.
     * This could be required on some buggy drivers which wants to have textures bound in a progressive order.
     * By default Babylon.js will try to let textures bound where they are and only update the samplers to point where the texture is
     */
    public disableTextureBindingOptimization = false;

    /**
     * Gets the audio engine
     * @see http://doc.babylonjs.com/how_to/playing_sounds_and_music
     * @ignorenaming
     */
    public static audioEngine: IAudioEngine;

    /**
     * Default AudioEngine factory responsible of creating the Audio Engine.
     * By default, this will create a BabylonJS Audio Engine if the workload has been embedded.
     */
    public static AudioEngineFactory: (hostElement: Nullable<HTMLElement>) => IAudioEngine;

    /**
     * Default offline support factory responsible of creating a tool used to store data locally.
     * By default, this will create a Database object if the workload has been embedded.
     */
    public static OfflineProviderFactory: (urlToScene: string, callbackManifestChecked: (checked: boolean) => any, disableManifestCheck: boolean) => IOfflineProvider;

    // Focus
    private _onFocus: () => void;
    private _onBlur: () => void;
    private _onCanvasPointerOut: (event: PointerEvent) => void;
    private _onCanvasBlur: () => void;
    private _onCanvasFocus: () => void;

    private _onFullscreenChange: () => void;
    private _onPointerLockChange: () => void;

    private _onVRDisplayPointerRestricted: () => void;
    private _onVRDisplayPointerUnrestricted: () => void;

    // VRDisplay connection
    private _onVrDisplayConnect: Nullable<(display: any) => void>;
    private _onVrDisplayDisconnect: Nullable<() => void>;
    private _onVrDisplayPresentChange: Nullable<() => void>;

    /**
     * Observable signaled when VR display mode changes
     */
    public onVRDisplayChangedObservable = new Observable<IDisplayChangedEventArgs>();
    /**
     * Observable signaled when VR request present is complete
     */
    public onVRRequestPresentComplete = new Observable<boolean>();
    /**
     * Observable signaled when VR request present starts
     */
    public onVRRequestPresentStart = new Observable<Engine>();

    private _hardwareScalingLevel: number;
    /** @hidden */
    protected _caps: EngineCapabilities;
    private _pointerLockRequested: boolean;
    private _isStencilEnable: boolean;
    private _colorWrite = true;

    private _loadingScreen: ILoadingScreen;

    /** @hidden */
    public _drawCalls = new PerfCounter();
    /** @hidden */
    public _textureCollisions = new PerfCounter();

    private _glVersion: string;
    private _glRenderer: string;
    private _glVendor: string;

    private _videoTextureSupported: boolean;

    private _renderingQueueLaunched = false;
    private _activeRenderLoops = new Array<() => void>();

    // Deterministic lockstepMaxSteps
    private _deterministicLockstep: boolean = false;
    private _lockstepMaxSteps: number = 4;

    // Lost context
    /**
     * Observable signaled when a context lost event is raised
     */
    public onContextLostObservable = new Observable<Engine>();
    /**
     * Observable signaled when a context restored event is raised
     */
    public onContextRestoredObservable = new Observable<Engine>();
    private _onContextLost: (evt: Event) => void;
    private _onContextRestored: (evt: Event) => void;
    private _contextWasLost = false;
    private _doNotHandleContextLost = false;

    /**
     * Gets or sets a boolean indicating if resources should be retained to be able to handle context lost events
     * @see http://doc.babylonjs.com/how_to/optimizing_your_scene#handling-webgl-context-lost
     */
    public get doNotHandleContextLost(): boolean {
        return this._doNotHandleContextLost;
    }

    public set doNotHandleContextLost(value: boolean) {
        this._doNotHandleContextLost = value;
    }

    // FPS
    private _performanceMonitor = new PerformanceMonitor();
    private _fps = 60;
    private _deltaTime = 0;
    /**
     * Turn this value on if you want to pause FPS computation when in background
     */
    public disablePerformanceMonitorInBackground = false;

    /**
     * Gets the performance monitor attached to this engine
     * @see http://doc.babylonjs.com/how_to/optimizing_your_scene#engineinstrumentation
     */
    public get performanceMonitor(): PerformanceMonitor {
        return this._performanceMonitor;
    }

    // States
    /** @hidden */
    protected _depthCullingState = new _DepthCullingState();
    /** @hidden */
    protected _stencilState = new _StencilState();
    /** @hidden */
    protected _alphaState = new _AlphaState();
    /** @hidden */
    protected _alphaMode = Engine.ALPHA_DISABLE;

    // Cache
    protected _internalTexturesCache = new Array<InternalTexture>();
    /** @hidden */
    protected _activeChannel = 0;
    private _currentTextureChannel = -1;
    /** @hidden */
    protected _boundTexturesCache: { [key: string]: Nullable<InternalTexture> } = {};
    /** @hidden */
    protected _currentEffect: Nullable<Effect>;
    /** @hidden */
    protected _currentProgram: Nullable<WebGLProgram>;
    private _compiledEffects: { [key: string]: Effect } = {};
    private _vertexAttribArraysEnabled: boolean[] = [];
    /** @hidden */
    protected _cachedViewport: Nullable<Viewport>;
    private _cachedVertexArrayObject: Nullable<WebGLVertexArrayObject>;
    /** @hidden */
    protected _cachedVertexBuffers: any;
    /** @hidden */
    protected _cachedIndexBuffer: Nullable<WebGLBuffer>;
    /** @hidden */
    protected _cachedEffectForVertexBuffers: Nullable<Effect>;
    /** @hidden */
    protected _currentRenderTarget: Nullable<InternalTexture>;
    private _uintIndicesCurrentlySet = false;
    private _currentBoundBuffer = new Array<Nullable<WebGLBuffer>>();
    /** @hidden */
    protected _currentFramebuffer: Nullable<WebGLFramebuffer> = null;
    private _currentBufferPointers = new Array<BufferPointer>();
    private _currentInstanceLocations = new Array<number>();
    private _currentInstanceBuffers = new Array<WebGLBuffer>();
    private _textureUnits: Int32Array;
    private _firstBoundInternalTextureTracker = new DummyInternalTextureTracker();
    private _lastBoundInternalTextureTracker = new DummyInternalTextureTracker();

    private _workingCanvas: Nullable<HTMLCanvasElement>;
    private _workingContext: Nullable<CanvasRenderingContext2D>;
    private _rescalePostProcess: PostProcess;

    private _dummyFramebuffer: WebGLFramebuffer;

    private _externalData: StringDictionary<Object>;
    private _bindedRenderFunction: any;

    private _vaoRecordInProgress = false;
    private _mustWipeVertexAttributes = false;

    private _emptyTexture: Nullable<InternalTexture>;
    private _emptyCubeTexture: Nullable<InternalTexture>;
    private _emptyTexture3D: Nullable<InternalTexture>;

    /** @hidden */
    public _frameHandler: number;

    private _nextFreeTextureSlots = new Array<number>();
    private _maxSimultaneousTextures = 0;

    private _activeRequests = new Array<IFileRequest>();

    // Hardware supported Compressed Textures
    private _texturesSupported = new Array<string>();
    private _textureFormatInUse: Nullable<string>;

    /**
     * Gets the list of texture formats supported
     */
    public get texturesSupported(): Array<string> {
        return this._texturesSupported;
    }

    /**
     * Gets the list of texture formats in use
     */
    public get textureFormatInUse(): Nullable<string> {
        return this._textureFormatInUse;
    }

    /**
     * Gets the current viewport
     */
    public get currentViewport(): Nullable<Viewport> {
        return this._cachedViewport;
    }

    /**
     * Gets the default empty texture
     */
    public get emptyTexture(): InternalTexture {
        if (!this._emptyTexture) {
            this._emptyTexture = this.createRawTexture(new Uint8Array(4), 1, 1, Engine.TEXTUREFORMAT_RGBA, false, false, Engine.TEXTURE_NEAREST_SAMPLINGMODE);
        }

        return this._emptyTexture;
    }

    /**
     * Gets the default empty 3D texture
     */
    public get emptyTexture3D(): InternalTexture {
        if (!this._emptyTexture3D) {
            this._emptyTexture3D = this.createRawTexture3D(new Uint8Array(4), 1, 1, 1, Engine.TEXTUREFORMAT_RGBA, false, false, Engine.TEXTURE_NEAREST_SAMPLINGMODE);
        }

        return this._emptyTexture3D;
    }

    /**
     * Gets the default empty cube texture
     */
    public get emptyCubeTexture(): InternalTexture {
        if (!this._emptyCubeTexture) {
            var faceData = new Uint8Array(4);
            var cubeData = [faceData, faceData, faceData, faceData, faceData, faceData];
            this._emptyCubeTexture = this.createRawCubeTexture(cubeData, 1, Engine.TEXTUREFORMAT_RGBA, Engine.TEXTURETYPE_UNSIGNED_INT, false, false, Engine.TEXTURE_NEAREST_SAMPLINGMODE);
        }

        return this._emptyCubeTexture;
    }

    /**
     * Defines whether the engine has been created with the premultipliedAlpha option on or not.
     */
    public readonly premultipliedAlpha: boolean = true;

    /**
     * Creates a new engine
     * @param canvasOrContext defines the canvas or WebGL context to use for rendering. If you provide a WebGL context, Babylon.js will not hook events on the canvas (like pointers, keyboards, etc...) so no event observables will be available. This is mostly used when Babylon.js is used as a plugin on a system which alreay used the WebGL context
     * @param antialias defines enable antialiasing (default: false)
     * @param options defines further options to be sent to the getContext() function
     * @param adaptToDeviceRatio defines whether to adapt to the device's viewport characteristics (default: false)
     */
    constructor(canvasOrContext: Nullable<HTMLCanvasElement | WebGLRenderingContext>, antialias?: boolean, options?: EngineOptions, adaptToDeviceRatio: boolean = false) {

        // Register promises
        PromisePolyfill.Apply();

        let canvas: Nullable<HTMLCanvasElement> = null;
        Engine.Instances.push(this);

        if (!canvasOrContext) {
            return;
        }

        options = options || {};

        if ((<HTMLCanvasElement>canvasOrContext).getContext) {
            canvas = <HTMLCanvasElement>canvasOrContext;
            this._renderingCanvas = canvas;

            if (antialias != null) {
                options.antialias = antialias;
            }

            if (options.deterministicLockstep === undefined) {
                options.deterministicLockstep = false;
            }

            if (options.lockstepMaxSteps === undefined) {
                options.lockstepMaxSteps = 4;
            }

            if (options.preserveDrawingBuffer === undefined) {
                options.preserveDrawingBuffer = false;
            }

            if (options.audioEngine === undefined) {
                options.audioEngine = true;
            }

            if (options.stencil === undefined) {
                options.stencil = true;
            }

            if (options.premultipliedAlpha === false) {
                this.premultipliedAlpha = false;
            }

            this._deterministicLockstep = options.deterministicLockstep;
            this._lockstepMaxSteps = options.lockstepMaxSteps;
            this._doNotHandleContextLost = options.doNotHandleContextLost ? true : false;

            // Exceptions
            if (navigator && navigator.userAgent) {
                let ua = navigator.userAgent;

                for (var exception of Engine.ExceptionList) {
                    let key = exception.key;
                    let targets = exception.targets;

                    if (ua.indexOf(key) > -1) {
                        if (exception.capture && exception.captureConstraint) {
                            let capture = exception.capture;
                            let constraint = exception.captureConstraint;

                            let regex = new RegExp(capture);
                            let matches = regex.exec(ua);

                            if (matches && matches.length > 0) {
                                let capturedValue = parseInt(matches[matches.length - 1]);
                                if (capturedValue >= constraint) {
                                    continue;
                                }
                            }
                        }

                        for (var target of targets) {
                            switch (target) {
                                case "uniformBuffer":
                                    this.disableUniformBuffers = true;
                                    break;
                                case "textureBindingOptimization":
                                    this.disableTextureBindingOptimization = true;
                                    break;
                            }
                        }
                    }
                }
            }

            // GL
            if (!options.disableWebGL2Support) {
                try {
                    this._gl = <any>(canvas.getContext("webgl2", options) || canvas.getContext("experimental-webgl2", options));
                    if (this._gl) {
                        this._webGLVersion = 2.0;

                        // Prevent weird browsers to lie :-)
                        if (!this._gl.deleteQuery) {
                            this._webGLVersion = 1.0;
                        }
                    }
                } catch (e) {
                    // Do nothing
                }
            }

            if (!this._gl) {
                if (!canvas) {
                    throw new Error("The provided canvas is null or undefined.");
                }
                try {
                    this._gl = <WebGLRenderingContext>(canvas.getContext("webgl", options) || canvas.getContext("experimental-webgl", options));
                } catch (e) {
                    throw new Error("WebGL not supported");
                }
            }

            if (!this._gl) {
                throw new Error("WebGL not supported");
            }

            // Ensures a consistent color space unpacking of textures cross browser.
            this._gl.pixelStorei(this._gl.UNPACK_COLORSPACE_CONVERSION_WEBGL, this._gl.NONE);

            this._onCanvasFocus = () => {
                this.onCanvasFocusObservable.notifyObservers(this);
            };

            this._onCanvasBlur = () => {
                this.onCanvasBlurObservable.notifyObservers(this);
            };

            canvas.addEventListener("focus", this._onCanvasFocus);
            canvas.addEventListener("blur", this._onCanvasBlur);

            this._onBlur = () => {
                if (this.disablePerformanceMonitorInBackground) {
                    this._performanceMonitor.disable();
                }
                this._windowIsBackground = true;
            };

            this._onFocus = () => {
                if (this.disablePerformanceMonitorInBackground) {
                    this._performanceMonitor.enable();
                }
                this._windowIsBackground = false;
            };

            this._onCanvasPointerOut = (ev) => {
                this.onCanvasPointerOutObservable.notifyObservers(ev);
            };

            if (DomManagement.IsWindowObjectExist()) {
                window.addEventListener("blur", this._onBlur);
                window.addEventListener("focus", this._onFocus);
            }

            canvas.addEventListener("pointerout", this._onCanvasPointerOut);

            // Context lost
            if (!this._doNotHandleContextLost) {
                this._onContextLost = (evt: Event) => {
                    evt.preventDefault();
                    this._contextWasLost = true;
                    Logger.Warn("WebGL context lost.");

                    this.onContextLostObservable.notifyObservers(this);
                };

                this._onContextRestored = () => {
                    // Adding a timeout to avoid race condition at browser level
                    setTimeout(() => {
                        // Rebuild gl context
                        this._initGLContext();
                        // Rebuild effects
                        this._rebuildEffects();
                        // Rebuild textures
                        this._rebuildInternalTextures();
                        // Rebuild buffers
                        this._rebuildBuffers();
                        // Cache
                        this.wipeCaches(true);
                        Logger.Warn("WebGL context successfully restored.");
                        this.onContextRestoredObservable.notifyObservers(this);
                        this._contextWasLost = false;
                    }, 0);
                };

                canvas.addEventListener("webglcontextlost", this._onContextLost, false);
                canvas.addEventListener("webglcontextrestored", this._onContextRestored, false);
            }

            if (!options.doNotHandleTouchAction) {
                this._disableTouchAction();
            }
        } else {
            this._gl = <WebGLRenderingContext>canvasOrContext;
            this._renderingCanvas = this._gl.canvas;

            if (this._gl.renderbufferStorageMultisample) {
                this._webGLVersion = 2.0;
            }

            const attributes = this._gl.getContextAttributes();
            if (attributes) {
                options.stencil = attributes.stencil;
            }
        }

        if (options.useHighPrecisionFloats !== undefined) {
            this._highPrecisionShadersAllowed = options.useHighPrecisionFloats;
        }

        // Viewport
        const devicePixelRatio = DomManagement.IsWindowObjectExist() ? (window.devicePixelRatio || 1.0) : 1.0;

        var limitDeviceRatio = options.limitDeviceRatio || devicePixelRatio;
        this._hardwareScalingLevel = adaptToDeviceRatio ? 1.0 / Math.min(limitDeviceRatio, devicePixelRatio) : 1.0;
        this.resize();

        this._isStencilEnable = options.stencil ? true : false;
        this._initGLContext();

        if (canvas) {
            let anyDoc = document as any;

            // Fullscreen
            this._onFullscreenChange = () => {

                if (anyDoc.fullscreen !== undefined) {
                    this.isFullscreen = anyDoc.fullscreen;
                } else if (anyDoc.mozFullScreen !== undefined) {
                    this.isFullscreen = anyDoc.mozFullScreen;
                } else if (anyDoc.webkitIsFullScreen !== undefined) {
                    this.isFullscreen = anyDoc.webkitIsFullScreen;
                } else if (anyDoc.msIsFullScreen !== undefined) {
                    this.isFullscreen = anyDoc.msIsFullScreen;
                }

                // Pointer lock
                if (this.isFullscreen && this._pointerLockRequested && canvas) {
                    canvas.requestPointerLock = canvas.requestPointerLock ||
                        canvas.msRequestPointerLock ||
                        canvas.mozRequestPointerLock ||
                        canvas.webkitRequestPointerLock;

                    if (canvas.requestPointerLock) {
                        canvas.requestPointerLock();
                    }
                }
            };

            document.addEventListener("fullscreenchange", this._onFullscreenChange, false);
            document.addEventListener("mozfullscreenchange", this._onFullscreenChange, false);
            document.addEventListener("webkitfullscreenchange", this._onFullscreenChange, false);
            document.addEventListener("msfullscreenchange", this._onFullscreenChange, false);

            // Pointer lock
            this._onPointerLockChange = () => {
                this.isPointerLock = (anyDoc.mozPointerLockElement === canvas ||
                    anyDoc.webkitPointerLockElement === canvas ||
                    anyDoc.msPointerLockElement === canvas ||
                    anyDoc.pointerLockElement === canvas
                );
            };

            document.addEventListener("pointerlockchange", this._onPointerLockChange, false);
            document.addEventListener("mspointerlockchange", this._onPointerLockChange, false);
            document.addEventListener("mozpointerlockchange", this._onPointerLockChange, false);
            document.addEventListener("webkitpointerlockchange", this._onPointerLockChange, false);

            this._onVRDisplayPointerRestricted = () => {
                if (canvas) {
                    canvas.requestPointerLock();
                }
            };

            this._onVRDisplayPointerUnrestricted = () => {
                if (!anyDoc.exitPointerLock) {
                    return;
                }
                anyDoc.exitPointerLock();
            };

            if (DomManagement.IsWindowObjectExist()) {
                window.addEventListener('vrdisplaypointerrestricted', this._onVRDisplayPointerRestricted, false);
                window.addEventListener('vrdisplaypointerunrestricted', this._onVRDisplayPointerUnrestricted, false);
            }
        }

        // Create Audio Engine if needed.
        if (!Engine.audioEngine && options.audioEngine && Engine.AudioEngineFactory) {
            Engine.audioEngine = Engine.AudioEngineFactory(this.getRenderingCanvas());
        }

        // Prepare buffer pointers
        for (var i = 0; i < this._caps.maxVertexAttribs; i++) {
            this._currentBufferPointers[i] = new BufferPointer();
        }

        this._linkTrackers(this._firstBoundInternalTextureTracker, this._lastBoundInternalTextureTracker);

        // Load WebVR Devices
        if (options.autoEnableWebVR) {
            this.initWebVR();
        }

        // Detect if we are running on a faulty buggy OS.
        this._badOS = /iPad/i.test(navigator.userAgent) || /iPhone/i.test(navigator.userAgent);

        // Detect if we are running on a faulty buggy desktop OS.
        this._badDesktopOS = /^((?!chrome|android).)*safari/i.test(navigator.userAgent);

        console.log(`Babylon.js v${Engine.Version} - ${this.description}`);

        this.enableOfflineSupport = Engine.OfflineProviderFactory !== undefined;
    }

    private _disableTouchAction(): void {
        if (!this._renderingCanvas) {
            return;
        }

        this._renderingCanvas.setAttribute("touch-action", "none");
        this._renderingCanvas.style.touchAction = "none";
        this._renderingCanvas.style.msTouchAction = "none";
    }

    private _rebuildInternalTextures(): void {
        let currentState = this._internalTexturesCache.slice(); // Do a copy because the rebuild will add proxies

        for (var internalTexture of currentState) {
            internalTexture._rebuild();
        }
    }

    private _rebuildEffects(): void {
        for (var key in this._compiledEffects) {
            let effect = <Effect>this._compiledEffects[key];

            effect._prepareEffect();
        }

        Effect.ResetCache();
    }

    /**
     * Gets a boolean indicating if all created effects are ready
     * @returns true if all effects are ready
     */
    public areAllEffectsReady(): boolean {
        for (var key in this._compiledEffects) {
            let effect = <Effect>this._compiledEffects[key];

            if (!effect.isReady()) {
                return false;
            }
        }

        return true;
    }

    private _rebuildBuffers(): void {
        // Index / Vertex
        for (var scene of this.scenes) {
            scene.resetCachedMaterial();
            scene._rebuildGeometries();
            scene._rebuildTextures();
        }

        // Uniforms
        for (var uniformBuffer of this._uniformBuffers) {
            uniformBuffer._rebuild();
        }
    }

    private _initGLContext(): void {
        // Caps
        this._caps = new EngineCapabilities();
        this._caps.maxTexturesImageUnits = this._gl.getParameter(this._gl.MAX_TEXTURE_IMAGE_UNITS);
        this._caps.maxCombinedTexturesImageUnits = this._gl.getParameter(this._gl.MAX_COMBINED_TEXTURE_IMAGE_UNITS);
        this._caps.maxVertexTextureImageUnits = this._gl.getParameter(this._gl.MAX_VERTEX_TEXTURE_IMAGE_UNITS);
        this._caps.maxTextureSize = this._gl.getParameter(this._gl.MAX_TEXTURE_SIZE);
        this._caps.maxCubemapTextureSize = this._gl.getParameter(this._gl.MAX_CUBE_MAP_TEXTURE_SIZE);
        this._caps.maxRenderTextureSize = this._gl.getParameter(this._gl.MAX_RENDERBUFFER_SIZE);
        this._caps.maxVertexAttribs = this._gl.getParameter(this._gl.MAX_VERTEX_ATTRIBS);
        this._caps.maxVaryingVectors = this._gl.getParameter(this._gl.MAX_VARYING_VECTORS);
        this._caps.maxFragmentUniformVectors = this._gl.getParameter(this._gl.MAX_FRAGMENT_UNIFORM_VECTORS);
        this._caps.maxVertexUniformVectors = this._gl.getParameter(this._gl.MAX_VERTEX_UNIFORM_VECTORS);

        // Infos
        this._glVersion = this._gl.getParameter(this._gl.VERSION);

        var rendererInfo: any = this._gl.getExtension("WEBGL_debug_renderer_info");
        if (rendererInfo != null) {
            this._glRenderer = this._gl.getParameter(rendererInfo.UNMASKED_RENDERER_WEBGL);
            this._glVendor = this._gl.getParameter(rendererInfo.UNMASKED_VENDOR_WEBGL);
        }

        if (!this._glVendor) {
            this._glVendor = "Unknown vendor";
        }

        if (!this._glRenderer) {
            this._glRenderer = "Unknown renderer";
        }

        // Constants
        this._gl.HALF_FLOAT_OES = 0x8D61;   // Half floating-point type (16-bit).
        if (this._gl.RGBA16F !== 0x881A) {
            this._gl.RGBA16F = 0x881A;      // RGBA 16-bit floating-point color-renderable internal sized format.
        }
        if (this._gl.RGBA32F !== 0x8814) {
            this._gl.RGBA32F = 0x8814;      // RGBA 32-bit floating-point color-renderable internal sized format.
        }
        if (this._gl.DEPTH24_STENCIL8 !== 35056) {
            this._gl.DEPTH24_STENCIL8 = 35056;
        }

        // Extensions
        this._caps.standardDerivatives = this._webGLVersion > 1 || (this._gl.getExtension('OES_standard_derivatives') !== null);

        this._caps.astc = this._gl.getExtension('WEBGL_compressed_texture_astc') || this._gl.getExtension('WEBKIT_WEBGL_compressed_texture_astc');
        this._caps.s3tc = this._gl.getExtension('WEBGL_compressed_texture_s3tc') || this._gl.getExtension('WEBKIT_WEBGL_compressed_texture_s3tc');
        this._caps.pvrtc = this._gl.getExtension('WEBGL_compressed_texture_pvrtc') || this._gl.getExtension('WEBKIT_WEBGL_compressed_texture_pvrtc');
        this._caps.etc1 = this._gl.getExtension('WEBGL_compressed_texture_etc1') || this._gl.getExtension('WEBKIT_WEBGL_compressed_texture_etc1');
        this._caps.etc2 = this._gl.getExtension('WEBGL_compressed_texture_etc') || this._gl.getExtension('WEBKIT_WEBGL_compressed_texture_etc') ||
            this._gl.getExtension('WEBGL_compressed_texture_es3_0'); // also a requirement of OpenGL ES 3

        this._caps.textureAnisotropicFilterExtension = this._gl.getExtension('EXT_texture_filter_anisotropic') || this._gl.getExtension('WEBKIT_EXT_texture_filter_anisotropic') || this._gl.getExtension('MOZ_EXT_texture_filter_anisotropic');
        this._caps.maxAnisotropy = this._caps.textureAnisotropicFilterExtension ? this._gl.getParameter(this._caps.textureAnisotropicFilterExtension.MAX_TEXTURE_MAX_ANISOTROPY_EXT) : 0;
        this._caps.uintIndices = this._webGLVersion > 1 || this._gl.getExtension('OES_element_index_uint') !== null;
        this._caps.fragmentDepthSupported = this._webGLVersion > 1 || this._gl.getExtension('EXT_frag_depth') !== null;
        this._caps.highPrecisionShaderSupported = false;
        this._caps.timerQuery = this._gl.getExtension('EXT_disjoint_timer_query_webgl2') || this._gl.getExtension("EXT_disjoint_timer_query");
        if (this._caps.timerQuery) {
            if (this._webGLVersion === 1) {
                this._gl.getQuery = (<any>this._caps.timerQuery).getQueryEXT.bind(this._caps.timerQuery);
            }
            this._caps.canUseTimestampForTimerQuery = this._gl.getQuery(this._caps.timerQuery.TIMESTAMP_EXT, this._caps.timerQuery.QUERY_COUNTER_BITS_EXT) > 0;
        }

        // Checks if some of the format renders first to allow the use of webgl inspector.
        this._caps.colorBufferFloat = this._webGLVersion > 1 && this._gl.getExtension('EXT_color_buffer_float');

        this._caps.textureFloat = (this._webGLVersion > 1 || this._gl.getExtension('OES_texture_float')) ? true : false;
        this._caps.textureFloatLinearFiltering = this._caps.textureFloat && this._gl.getExtension('OES_texture_float_linear') ? true : false;
        this._caps.textureFloatRender = this._caps.textureFloat && this._canRenderToFloatFramebuffer() ? true : false;

        this._caps.textureHalfFloat = (this._webGLVersion > 1 || this._gl.getExtension('OES_texture_half_float')) ? true : false;
        this._caps.textureHalfFloatLinearFiltering = (this._webGLVersion > 1 || (this._caps.textureHalfFloat && this._gl.getExtension('OES_texture_half_float_linear'))) ? true : false;
        if (this._webGLVersion > 1) {
            this._gl.HALF_FLOAT_OES = 0x140B;
        }
        this._caps.textureHalfFloatRender = this._caps.textureHalfFloat && this._canRenderToHalfFloatFramebuffer();

        this._caps.textureLOD = (this._webGLVersion > 1 || this._gl.getExtension('EXT_shader_texture_lod')) ? true : false;

        // Draw buffers
        if (this._webGLVersion > 1) {
            this._caps.drawBuffersExtension = true;
        } else {
            var drawBuffersExtension = this._gl.getExtension('WEBGL_draw_buffers');

            if (drawBuffersExtension !== null) {
                this._caps.drawBuffersExtension = true;
                this._gl.drawBuffers = drawBuffersExtension.drawBuffersWEBGL.bind(drawBuffersExtension);
                this._gl.DRAW_FRAMEBUFFER = this._gl.FRAMEBUFFER;

                for (var i = 0; i < 16; i++) {
                    (<any>this._gl)["COLOR_ATTACHMENT" + i + "_WEBGL"] = (<any>drawBuffersExtension)["COLOR_ATTACHMENT" + i + "_WEBGL"];
                }
            } else {
                this._caps.drawBuffersExtension = false;
            }
        }

        // Shader compiler threads
        this._caps.parallelShaderCompile = this._gl.getExtension('KHR_parallel_shader_compile');

        // Depth Texture
        if (this._webGLVersion > 1) {
            this._caps.depthTextureExtension = true;
        } else {
            var depthTextureExtension = this._gl.getExtension('WEBGL_depth_texture');

            if (depthTextureExtension != null) {
                this._caps.depthTextureExtension = true;
                this._gl.UNSIGNED_INT_24_8 = depthTextureExtension.UNSIGNED_INT_24_8_WEBGL;
            }
        }

        // Vertex array object
        if (this._webGLVersion > 1) {
            this._caps.vertexArrayObject = true;
        } else {
            var vertexArrayObjectExtension = this._gl.getExtension('OES_vertex_array_object');

            if (vertexArrayObjectExtension != null) {
                this._caps.vertexArrayObject = true;
                this._gl.createVertexArray = vertexArrayObjectExtension.createVertexArrayOES.bind(vertexArrayObjectExtension);
                this._gl.bindVertexArray = vertexArrayObjectExtension.bindVertexArrayOES.bind(vertexArrayObjectExtension);
                this._gl.deleteVertexArray = vertexArrayObjectExtension.deleteVertexArrayOES.bind(vertexArrayObjectExtension);
            } else {
                this._caps.vertexArrayObject = false;
            }
        }

        // Instances count
        if (this._webGLVersion > 1) {
            this._caps.instancedArrays = true;
        } else {
            var instanceExtension = <ANGLE_instanced_arrays>this._gl.getExtension('ANGLE_instanced_arrays');

            if (instanceExtension != null) {
                this._caps.instancedArrays = true;
                this._gl.drawArraysInstanced = instanceExtension.drawArraysInstancedANGLE.bind(instanceExtension);
                this._gl.drawElementsInstanced = instanceExtension.drawElementsInstancedANGLE.bind(instanceExtension);
                this._gl.vertexAttribDivisor = instanceExtension.vertexAttribDivisorANGLE.bind(instanceExtension);
            } else {
                this._caps.instancedArrays = false;
            }
        }

        // Intelligently add supported compressed formats in order to check for.
        // Check for ASTC support first as it is most powerful and to be very cross platform.
        // Next PVRTC & DXT, which are probably superior to ETC1/2.
        // Likely no hardware which supports both PVR & DXT, so order matters little.
        // ETC2 is newer and handles ETC1 (no alpha capability), so check for first.
        if (this._caps.astc) { this.texturesSupported.push('-astc.ktx'); }
        if (this._caps.s3tc) { this.texturesSupported.push('-dxt.ktx'); }
        if (this._caps.pvrtc) { this.texturesSupported.push('-pvrtc.ktx'); }
        if (this._caps.etc2) { this.texturesSupported.push('-etc2.ktx'); }
        if (this._caps.etc1) { this.texturesSupported.push('-etc1.ktx'); }

        if (this._gl.getShaderPrecisionFormat) {
            var vertex_highp = this._gl.getShaderPrecisionFormat(this._gl.VERTEX_SHADER, this._gl.HIGH_FLOAT);
            var fragment_highp = this._gl.getShaderPrecisionFormat(this._gl.FRAGMENT_SHADER, this._gl.HIGH_FLOAT);

            if (vertex_highp && fragment_highp) {
                this._caps.highPrecisionShaderSupported = vertex_highp.precision !== 0 && fragment_highp.precision !== 0;
            }
        }

        // Depth buffer
        this.setDepthBuffer(true);
        this.setDepthFunctionToLessOrEqual();
        this.setDepthWrite(true);

        // Texture maps
        this._maxSimultaneousTextures = this._caps.maxCombinedTexturesImageUnits;
        for (let slot = 0; slot < this._maxSimultaneousTextures; slot++) {
            this._nextFreeTextureSlots.push(slot);
        }
    }

    /**
     * Gets version of the current webGL context
     */
    public get webGLVersion(): number {
        return this._webGLVersion;
    }

    /**
     * Returns true if the stencil buffer has been enabled through the creation option of the context.
     */
    public get isStencilEnable(): boolean {
        return this._isStencilEnable;
    }

    private _prepareWorkingCanvas(): void {
        if (this._workingCanvas) {
            return;
        }

        this._workingCanvas = document.createElement("canvas");
        let context = this._workingCanvas.getContext("2d");

        if (context) {
            this._workingContext = context;
        }
    }

    /**
     * Reset the texture cache to empty state
     */
    public resetTextureCache() {
        for (var key in this._boundTexturesCache) {
            if (!this._boundTexturesCache.hasOwnProperty(key)) {
                continue;
            }
            let boundTexture = this._boundTexturesCache[key];
            if (boundTexture) {
                this._removeDesignatedSlot(boundTexture);
            }
            this._boundTexturesCache[key] = null;
        }

        if (!this.disableTextureBindingOptimization) {
            this._nextFreeTextureSlots = [];
            for (let slot = 0; slot < this._maxSimultaneousTextures; slot++) {
                this._nextFreeTextureSlots.push(slot);
            }
        }

        this._currentTextureChannel = -1;
    }

    /**
     * Gets a boolean indicating that the engine is running in deterministic lock step mode
     * @see http://doc.babylonjs.com/babylon101/animations#deterministic-lockstep
     * @returns true if engine is in deterministic lock step mode
     */
    public isDeterministicLockStep(): boolean {
        return this._deterministicLockstep;
    }

    /**
     * Gets the max steps when engine is running in deterministic lock step
     * @see http://doc.babylonjs.com/babylon101/animations#deterministic-lockstep
     * @returns the max steps
     */
    public getLockstepMaxSteps(): number {
        return this._lockstepMaxSteps;
    }

    /**
     * Gets an object containing information about the current webGL context
     * @returns an object containing the vender, the renderer and the version of the current webGL context
     */
    public getGlInfo() {
        return {
            vendor: this._glVendor,
            renderer: this._glRenderer,
            version: this._glVersion
        };
    }

    /**
     * Gets current aspect ratio
     * @param camera defines the camera to use to get the aspect ratio
     * @param useScreen defines if screen size must be used (or the current render target if any)
     * @returns a number defining the aspect ratio
     */
    public getAspectRatio(camera: Camera, useScreen = false): number {
        var viewport = camera.viewport;
        return (this.getRenderWidth(useScreen) * viewport.width) / (this.getRenderHeight(useScreen) * viewport.height);
    }

    /**
     * Gets current screen aspect ratio
     * @returns a number defining the aspect ratio
     */
    public getScreenAspectRatio(): number {
        return (this.getRenderWidth(true)) / (this.getRenderHeight(true));
    }

    /**
     * Gets the current render width
     * @param useScreen defines if screen size must be used (or the current render target if any)
     * @returns a number defining the current render width
     */
    public getRenderWidth(useScreen = false): number {
        if (!useScreen && this._currentRenderTarget) {
            return this._currentRenderTarget.width;
        }

        return this._gl.drawingBufferWidth;
    }

    /**
     * Gets the current render height
     * @param useScreen defines if screen size must be used (or the current render target if any)
     * @returns a number defining the current render height
     */
    public getRenderHeight(useScreen = false): number {
        if (!useScreen && this._currentRenderTarget) {
            return this._currentRenderTarget.height;
        }

        return this._gl.drawingBufferHeight;
    }

    /**
     * Gets the HTML canvas attached with the current webGL context
     * @returns a HTML canvas
     */
    public getRenderingCanvas(): Nullable<HTMLCanvasElement> {
        return this._renderingCanvas;
    }

    /**
     * Gets the client rect of the HTML canvas attached with the current webGL context
     * @returns a client rectanglee
     */
    public getRenderingCanvasClientRect(): Nullable<ClientRect> {
        if (!this._renderingCanvas) {
            return null;
        }
        return this._renderingCanvas.getBoundingClientRect();
    }

    /**
     * Defines the hardware scaling level.
     * By default the hardware scaling level is computed from the window device ratio.
     * if level = 1 then the engine will render at the exact resolution of the canvas. If level = 0.5 then the engine will render at twice the size of the canvas.
     * @param level defines the level to use
     */
    public setHardwareScalingLevel(level: number): void {
        this._hardwareScalingLevel = level;
        this.resize();
    }

    /**
     * Gets the current hardware scaling level.
     * By default the hardware scaling level is computed from the window device ratio.
     * if level = 1 then the engine will render at the exact resolution of the canvas. If level = 0.5 then the engine will render at twice the size of the canvas.
     * @returns a number indicating the current hardware scaling level
     */
    public getHardwareScalingLevel(): number {
        return this._hardwareScalingLevel;
    }

    /**
     * Gets the list of loaded textures
     * @returns an array containing all loaded textures
     */
    public getLoadedTexturesCache(): InternalTexture[] {
        return this._internalTexturesCache;
    }

    /**
     * Gets the object containing all engine capabilities
     * @returns the EngineCapabilities object
     */
    public getCaps(): EngineCapabilities {
        return this._caps;
    }

    /**
     * Gets the current depth function
     * @returns a number defining the depth function
     */
    public getDepthFunction(): Nullable<number> {
        return this._depthCullingState.depthFunc;
    }

    /**
     * Sets the current depth function
     * @param depthFunc defines the function to use
     */
    public setDepthFunction(depthFunc: number) {
        this._depthCullingState.depthFunc = depthFunc;
    }

    /**
     * Sets the current depth function to GREATER
     */
    public setDepthFunctionToGreater(): void {
        this._depthCullingState.depthFunc = this._gl.GREATER;
    }

    /**
     * Sets the current depth function to GEQUAL
     */
    public setDepthFunctionToGreaterOrEqual(): void {
        this._depthCullingState.depthFunc = this._gl.GEQUAL;
    }

    /**
     * Sets the current depth function to LESS
     */
    public setDepthFunctionToLess(): void {
        this._depthCullingState.depthFunc = this._gl.LESS;
    }

    /**
     * Sets the current depth function to LEQUAL
     */
    public setDepthFunctionToLessOrEqual(): void {
        this._depthCullingState.depthFunc = this._gl.LEQUAL;
    }

    /**
     * Gets a boolean indicating if stencil buffer is enabled
     * @returns the current stencil buffer state
     */
    public getStencilBuffer(): boolean {
        return this._stencilState.stencilTest;
    }

    /**
     * Enable or disable the stencil buffer
     * @param enable defines if the stencil buffer must be enabled or disabled
     */
    public setStencilBuffer(enable: boolean): void {
        this._stencilState.stencilTest = enable;
    }

    /**
     * Gets the current stencil mask
     * @returns a number defining the new stencil mask to use
     */
    public getStencilMask(): number {
        return this._stencilState.stencilMask;
    }

    /**
     * Sets the current stencil mask
     * @param mask defines the new stencil mask to use
     */
    public setStencilMask(mask: number): void {
        this._stencilState.stencilMask = mask;
    }

    /**
     * Gets the current stencil function
     * @returns a number defining the stencil function to use
     */
    public getStencilFunction(): number {
        return this._stencilState.stencilFunc;
    }

    /**
     * Gets the current stencil reference value
     * @returns a number defining the stencil reference value to use
     */
    public getStencilFunctionReference(): number {
        return this._stencilState.stencilFuncRef;
    }

    /**
     * Gets the current stencil mask
     * @returns a number defining the stencil mask to use
     */
    public getStencilFunctionMask(): number {
        return this._stencilState.stencilFuncMask;
    }

    /**
     * Sets the current stencil function
     * @param stencilFunc defines the new stencil function to use
     */
    public setStencilFunction(stencilFunc: number) {
        this._stencilState.stencilFunc = stencilFunc;
    }

    /**
     * Sets the current stencil reference
     * @param reference defines the new stencil reference to use
     */
    public setStencilFunctionReference(reference: number) {
        this._stencilState.stencilFuncRef = reference;
    }

    /**
     * Sets the current stencil mask
     * @param mask defines the new stencil mask to use
     */
    public setStencilFunctionMask(mask: number) {
        this._stencilState.stencilFuncMask = mask;
    }

    /**
     * Gets the current stencil operation when stencil fails
     * @returns a number defining stencil operation to use when stencil fails
     */
    public getStencilOperationFail(): number {
        return this._stencilState.stencilOpStencilFail;
    }

    /**
     * Gets the current stencil operation when depth fails
     * @returns a number defining stencil operation to use when depth fails
     */
    public getStencilOperationDepthFail(): number {
        return this._stencilState.stencilOpDepthFail;
    }

    /**
     * Gets the current stencil operation when stencil passes
     * @returns a number defining stencil operation to use when stencil passes
     */
    public getStencilOperationPass(): number {
        return this._stencilState.stencilOpStencilDepthPass;
    }

    /**
     * Sets the stencil operation to use when stencil fails
     * @param operation defines the stencil operation to use when stencil fails
     */
    public setStencilOperationFail(operation: number): void {
        this._stencilState.stencilOpStencilFail = operation;
    }

    /**
     * Sets the stencil operation to use when depth fails
     * @param operation defines the stencil operation to use when depth fails
     */
    public setStencilOperationDepthFail(operation: number): void {
        this._stencilState.stencilOpDepthFail = operation;
    }

    /**
     * Sets the stencil operation to use when stencil passes
     * @param operation defines the stencil operation to use when stencil passes
     */
    public setStencilOperationPass(operation: number): void {
        this._stencilState.stencilOpStencilDepthPass = operation;
    }

    /**
     * Sets a boolean indicating if the dithering state is enabled or disabled
     * @param value defines the dithering state
     */
    public setDitheringState(value: boolean): void {
        if (value) {
            this._gl.enable(this._gl.DITHER);
        } else {
            this._gl.disable(this._gl.DITHER);
        }
    }

    /**
     * Sets a boolean indicating if the rasterizer state is enabled or disabled
     * @param value defines the rasterizer state
     */
    public setRasterizerState(value: boolean): void {
        if (value) {
            this._gl.disable(this._gl.RASTERIZER_DISCARD);
        } else {
            this._gl.enable(this._gl.RASTERIZER_DISCARD);
        }
    }

    /**
     * stop executing a render loop function and remove it from the execution array
     * @param renderFunction defines the function to be removed. If not provided all functions will be removed.
     */
    public stopRenderLoop(renderFunction?: () => void): void {
        if (!renderFunction) {
            this._activeRenderLoops = [];
            return;
        }

        var index = this._activeRenderLoops.indexOf(renderFunction);

        if (index >= 0) {
            this._activeRenderLoops.splice(index, 1);
        }
    }

    /** @hidden */
    public _renderLoop(): void {
        if (!this._contextWasLost) {
            var shouldRender = true;
            if (!this.renderEvenInBackground && this._windowIsBackground) {
                shouldRender = false;
            }

            if (shouldRender) {
                // Start new frame
                this.beginFrame();

                for (var index = 0; index < this._activeRenderLoops.length; index++) {
                    var renderFunction = this._activeRenderLoops[index];

                    renderFunction();
                }

                // Present
                this.endFrame();
            }
        }

        if (this._activeRenderLoops.length > 0) {
            // Register new frame
            if (this.customAnimationFrameRequester) {
                this.customAnimationFrameRequester.requestID = Tools.QueueNewFrame(this.customAnimationFrameRequester.renderFunction || this._bindedRenderFunction, this.customAnimationFrameRequester);
                this._frameHandler = this.customAnimationFrameRequester.requestID;
            } else if (this._vrDisplay && this._vrDisplay.isPresenting) {
                this._frameHandler = Tools.QueueNewFrame(this._bindedRenderFunction, this._vrDisplay);
            } else {
                this._frameHandler = Tools.QueueNewFrame(this._bindedRenderFunction);
            }
        } else {
            this._renderingQueueLaunched = false;
        }
    }

    /**
     * Register and execute a render loop. The engine can have more than one render function
     * @param renderFunction defines the function to continuously execute
     */
    public runRenderLoop(renderFunction: () => void): void {
        if (this._activeRenderLoops.indexOf(renderFunction) !== -1) {
            return;
        }

        this._activeRenderLoops.push(renderFunction);

        if (!this._renderingQueueLaunched) {
            this._renderingQueueLaunched = true;
            this._bindedRenderFunction = this._renderLoop.bind(this);
            this._frameHandler = Tools.QueueNewFrame(this._bindedRenderFunction);
        }
    }

    /**
     * Toggle full screen mode
     * @param requestPointerLock defines if a pointer lock should be requested from the user
     */
    public switchFullscreen(requestPointerLock: boolean): void {
        if (this.isFullscreen) {
            this.exitFullscreen();
        } else {
            this.enterFullscreen(requestPointerLock);
        }
    }

    /**
     * Enters full screen mode
     * @param requestPointerLock defines if a pointer lock should be requested from the user
     */
    public enterFullscreen(requestPointerLock: boolean): void {
        if (!this.isFullscreen) {
            this._pointerLockRequested = requestPointerLock;
            if (this._renderingCanvas) {
                Tools.RequestFullscreen(this._renderingCanvas);
            }
        }
    }

    /**
     * Exits full screen mode
     */
    public exitFullscreen(): void {
        if (this.isFullscreen) {
            Tools.ExitFullscreen();
        }
    }

    /**
     * Clear the current render buffer or the current render target (if any is set up)
     * @param color defines the color to use
     * @param backBuffer defines if the back buffer must be cleared
     * @param depth defines if the depth buffer must be cleared
     * @param stencil defines if the stencil buffer must be cleared
     */
    public clear(color: Nullable<Color4>, backBuffer: boolean, depth: boolean, stencil: boolean = false): void {
        this.applyStates();

        var mode = 0;
        if (backBuffer && color) {
            this._gl.clearColor(color.r, color.g, color.b, color.a !== undefined ? color.a : 1.0);
            mode |= this._gl.COLOR_BUFFER_BIT;
        }
        if (depth) {
            this._gl.clearDepth(1.0);
            mode |= this._gl.DEPTH_BUFFER_BIT;
        }
        if (stencil) {
            this._gl.clearStencil(0);
            mode |= this._gl.STENCIL_BUFFER_BIT;
        }
        this._gl.clear(mode);
    }

    /**
     * Executes a scissor clear (ie. a clear on a specific portion of the screen)
     * @param x defines the x-coordinate of the top left corner of the clear rectangle
     * @param y defines the y-coordinate of the corner of the clear rectangle
     * @param width defines the width of the clear rectangle
     * @param height defines the height of the clear rectangle
     * @param clearColor defines the clear color
     */
    public scissorClear(x: number, y: number, width: number, height: number, clearColor: Color4): void {
        this.enableScissor(x, y, width, height);
        this.clear(clearColor, true, true, true);
        this.disableScissor();
    }

    /**
     * Enable scissor test on a specific rectangle (ie. render will only be executed on a specific portion of the screen)
     * @param x defines the x-coordinate of the top left corner of the clear rectangle
     * @param y defines the y-coordinate of the corner of the clear rectangle
     * @param width defines the width of the clear rectangle
     * @param height defines the height of the clear rectangle
     */
    public enableScissor(x: number, y: number, width: number, height: number): void {
        let gl = this._gl;

        // Change state
        gl.enable(gl.SCISSOR_TEST);
        gl.scissor(x, y, width, height);
    }

    /**
     * Disable previously set scissor test rectangle
     */
    public disableScissor() {
        let gl = this._gl;

        gl.disable(gl.SCISSOR_TEST);
    }

    private _viewportCached = new Vector4(0, 0, 0, 0);

    /** @hidden */
    public _viewport(x: number, y: number, width: number, height: number): void {
        if (x !== this._viewportCached.x ||
            y !== this._viewportCached.y ||
            width !== this._viewportCached.z ||
            height !== this._viewportCached.w) {
            this._viewportCached.x = x;
            this._viewportCached.y = y;
            this._viewportCached.z = width;
            this._viewportCached.w = height;

            this._gl.viewport(x, y, width, height);
        }
    }

    /**
     * Set the WebGL's viewport
     * @param viewport defines the viewport element to be used
     * @param requiredWidth defines the width required for rendering. If not provided the rendering canvas' width is used
     * @param requiredHeight defines the height required for rendering. If not provided the rendering canvas' height is used
     */
    public setViewport(viewport: Viewport, requiredWidth?: number, requiredHeight?: number): void {
        var width = requiredWidth || this.getRenderWidth();
        var height = requiredHeight || this.getRenderHeight();
        var x = viewport.x || 0;
        var y = viewport.y || 0;

        this._cachedViewport = viewport;

        this._viewport(x * width, y * height, width * viewport.width, height * viewport.height);
    }

    /**
     * Directly set the WebGL Viewport
     * @param x defines the x coordinate of the viewport (in screen space)
     * @param y defines the y coordinate of the viewport (in screen space)
     * @param width defines the width of the viewport (in screen space)
     * @param height defines the height of the viewport (in screen space)
     * @return the current viewport Object (if any) that is being replaced by this call. You can restore this viewport later on to go back to the original state
     */
    public setDirectViewport(x: number, y: number, width: number, height: number): Nullable<Viewport> {
        let currentViewport = this._cachedViewport;
        this._cachedViewport = null;

        this._viewport(x, y, width, height);

        return currentViewport;
    }

    /**
     * Begin a new frame
     */
    public beginFrame(): void {
        this.onBeginFrameObservable.notifyObservers(this);
        this._measureFps();
    }

    /**
     * Enf the current frame
     */
    public endFrame(): void {
        // Force a flush in case we are using a bad OS.
        if (this._badOS) {
            this.flushFramebuffer();
        }

        // Submit frame to the vr device, if enabled
        if (this._vrDisplay && this._vrDisplay.isPresenting) {
            // TODO: We should only submit the frame if we read frameData successfully.
            try {
                this._vrDisplay.submitFrame();
            } catch (e) {
                Tools.Warn("webVR submitFrame has had an unexpected failure: " + e);
            }
        }

        this.onEndFrameObservable.notifyObservers(this);
    }

    /**
     * Resize the view according to the canvas' size
     */
    public resize(): void {
        // We're not resizing the size of the canvas while in VR mode & presenting
        if (!(this._vrDisplay && this._vrDisplay.isPresenting)) {
            var width = this._renderingCanvas ? this._renderingCanvas.clientWidth : window.innerWidth;
            var height = this._renderingCanvas ? this._renderingCanvas.clientHeight : window.innerHeight;

            this.setSize(width / this._hardwareScalingLevel, height / this._hardwareScalingLevel);
        }
    }

    /**
     * Force a specific size of the canvas
     * @param width defines the new canvas' width
     * @param height defines the new canvas' height
     */
    public setSize(width: number, height: number): void {
        if (!this._renderingCanvas) {
            return;
        }

        if (this._renderingCanvas.width === width && this._renderingCanvas.height === height) {
            return;
        }

        this._renderingCanvas.width = width;
        this._renderingCanvas.height = height;

        for (var index = 0; index < this.scenes.length; index++) {
            var scene = this.scenes[index];

            for (var camIndex = 0; camIndex < scene.cameras.length; camIndex++) {
                var cam = scene.cameras[camIndex];

                cam._currentRenderId = 0;
            }
        }

        if (this.onResizeObservable.hasObservers) {
            this.onResizeObservable.notifyObservers(this);
        }
    }

    // WebVR functions

    /**
     * Gets a boolean indicating if a webVR device was detected
     * @returns true if a webVR device was detected
     */
    public isVRDevicePresent(): boolean {
        return !!this._vrDisplay;
    }

    /**
     * Gets the current webVR device
     * @returns the current webVR device (or null)
     */
    public getVRDevice(): any {
        return this._vrDisplay;
    }

    /**
     * Initializes a webVR display and starts listening to display change events
     * The onVRDisplayChangedObservable will be notified upon these changes
     * @returns The onVRDisplayChangedObservable
     */
    public initWebVR(): Observable<IDisplayChangedEventArgs> {
        this.initWebVRAsync();
        return this.onVRDisplayChangedObservable;
    }

    /**
     * Initializes a webVR display and starts listening to display change events
     * The onVRDisplayChangedObservable will be notified upon these changes
     * @returns A promise containing a VRDisplay and if vr is supported
     */
    public initWebVRAsync(): Promise<IDisplayChangedEventArgs> {
        var notifyObservers = () => {
            var eventArgs = {
                vrDisplay: this._vrDisplay,
                vrSupported: this._vrSupported
            };
            this.onVRDisplayChangedObservable.notifyObservers(eventArgs);
            this._webVRInitPromise = new Promise((res) => { res(eventArgs); });
        };

        if (!this._onVrDisplayConnect) {
            this._onVrDisplayConnect = (event) => {
                this._vrDisplay = event.display;
                notifyObservers();
            };
            this._onVrDisplayDisconnect = () => {
                this._vrDisplay.cancelAnimationFrame(this._frameHandler);
                this._vrDisplay = undefined;
                this._frameHandler = Tools.QueueNewFrame(this._bindedRenderFunction);
                notifyObservers();
            };
            this._onVrDisplayPresentChange = () => {
                this._vrExclusivePointerMode = this._vrDisplay && this._vrDisplay.isPresenting;
            };
            window.addEventListener('vrdisplayconnect', this._onVrDisplayConnect);
            window.addEventListener('vrdisplaydisconnect', this._onVrDisplayDisconnect);
            window.addEventListener('vrdisplaypresentchange', this._onVrDisplayPresentChange);
        }
        this._webVRInitPromise = this._webVRInitPromise || this._getVRDisplaysAsync();
        this._webVRInitPromise.then(notifyObservers);
        return this._webVRInitPromise;
    }

    /**
     * Call this function to switch to webVR mode
     * Will do nothing if webVR is not supported or if there is no webVR device
     * @see http://doc.babylonjs.com/how_to/webvr_camera
     */
    public enableVR() {
        if (this._vrDisplay && !this._vrDisplay.isPresenting) {
            var onResolved = () => {
                this.onVRRequestPresentComplete.notifyObservers(true);
                this._onVRFullScreenTriggered();
            };
            var onRejected = () => {
                this.onVRRequestPresentComplete.notifyObservers(false);
            };

            this.onVRRequestPresentStart.notifyObservers(this);
            this._vrDisplay.requestPresent([{ source: this.getRenderingCanvas() }]).then(onResolved).catch(onRejected);
        }
    }

    /**
     * Call this function to leave webVR mode
     * Will do nothing if webVR is not supported or if there is no webVR device
     * @see http://doc.babylonjs.com/how_to/webvr_camera
     */
    public disableVR() {
        if (this._vrDisplay && this._vrDisplay.isPresenting) {
            this._vrDisplay.exitPresent().then(this._onVRFullScreenTriggered).catch(this._onVRFullScreenTriggered);
        }
    }

    private _onVRFullScreenTriggered = () => {
        if (this._vrDisplay && this._vrDisplay.isPresenting) {
            //get the old size before we change
            this._oldSize = new Size(this.getRenderWidth(), this.getRenderHeight());
            this._oldHardwareScaleFactor = this.getHardwareScalingLevel();

            //get the width and height, change the render size
            var leftEye = this._vrDisplay.getEyeParameters('left');
            this.setHardwareScalingLevel(1);
            this.setSize(leftEye.renderWidth * 2, leftEye.renderHeight);
        } else {
            this.setHardwareScalingLevel(this._oldHardwareScaleFactor);
            this.setSize(this._oldSize.width, this._oldSize.height);
        }
    }

    private _getVRDisplaysAsync(): Promise<IDisplayChangedEventArgs> {
        return new Promise((res) => {
            if (navigator.getVRDisplays) {
                navigator.getVRDisplays().then((devices: Array<any>) => {
                    this._vrSupported = true;
                    // note that devices may actually be an empty array. This is fine;
                    // we expect this._vrDisplay to be undefined in this case.
                    this._vrDisplay = devices[0];
                    res({
                        vrDisplay: this._vrDisplay,
                        vrSupported: this._vrSupported
                    });
                });
            } else {
                this._vrDisplay = undefined;
                this._vrSupported = false;
                res({
                    vrDisplay: this._vrDisplay,
                    vrSupported: this._vrSupported
                });
            }
        });
    }

    /**
     * Binds the frame buffer to the specified texture.
     * @param texture The texture to render to or null for the default canvas
     * @param faceIndex The face of the texture to render to in case of cube texture
     * @param requiredWidth The width of the target to render to
     * @param requiredHeight The height of the target to render to
     * @param forceFullscreenViewport Forces the viewport to be the entire texture/screen if true
     * @param depthStencilTexture The depth stencil texture to use to render
     * @param lodLevel defines le lod level to bind to the frame buffer
     */
    public bindFramebuffer(texture: InternalTexture, faceIndex?: number, requiredWidth?: number, requiredHeight?: number, forceFullscreenViewport?: boolean, depthStencilTexture?: InternalTexture, lodLevel = 0): void {
        if (this._currentRenderTarget) {
            this.unBindFramebuffer(this._currentRenderTarget);
        }
        this._currentRenderTarget = texture;
        this.bindUnboundFramebuffer(texture._MSAAFramebuffer ? texture._MSAAFramebuffer : texture._framebuffer);
        var gl = this._gl;
        if (texture.isCube) {
            if (faceIndex === undefined) {
                faceIndex = 0;
            }
            gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_CUBE_MAP_POSITIVE_X + faceIndex, texture._webGLTexture, lodLevel);

            if (depthStencilTexture) {
                if (depthStencilTexture._generateStencilBuffer) {
                    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.TEXTURE_CUBE_MAP_POSITIVE_X + faceIndex, depthStencilTexture._webGLTexture, lodLevel);
                }
                else {
                    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.TEXTURE_CUBE_MAP_POSITIVE_X + faceIndex, depthStencilTexture._webGLTexture, lodLevel);
                }
            }
        }

        if (this._cachedViewport && !forceFullscreenViewport) {
            this.setViewport(this._cachedViewport, requiredWidth, requiredHeight);
        } else {
            if (!requiredWidth) {
                requiredWidth = texture.width;
                if (lodLevel) {
                    requiredWidth = requiredWidth / Math.pow(2, lodLevel);
                }
            }
            if (!requiredHeight) {
                requiredHeight = texture.height;
                if (lodLevel) {
                    requiredHeight = requiredHeight / Math.pow(2, lodLevel);
                }
            }

            this._viewport(0, 0, requiredWidth, requiredHeight);
        }

        this.wipeCaches();
    }

    private bindUnboundFramebuffer(framebuffer: Nullable<WebGLFramebuffer>) {
        if (this._currentFramebuffer !== framebuffer) {
            this._gl.bindFramebuffer(this._gl.FRAMEBUFFER, framebuffer);
            this._currentFramebuffer = framebuffer;
        }
    }

    /**
     * Unbind the current render target texture from the webGL context
     * @param texture defines the render target texture to unbind
     * @param disableGenerateMipMaps defines a boolean indicating that mipmaps must not be generated
     * @param onBeforeUnbind defines a function which will be called before the effective unbind
     */
    public unBindFramebuffer(texture: InternalTexture, disableGenerateMipMaps = false, onBeforeUnbind?: () => void): void {
        this._currentRenderTarget = null;

        // If MSAA, we need to bitblt back to main texture
        var gl = this._gl;

        if (texture._MSAAFramebuffer) {
            gl.bindFramebuffer(gl.READ_FRAMEBUFFER, texture._MSAAFramebuffer);
            gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, texture._framebuffer);
            gl.blitFramebuffer(0, 0, texture.width, texture.height,
                0, 0, texture.width, texture.height,
                gl.COLOR_BUFFER_BIT, gl.NEAREST);
        }

        if (texture.generateMipMaps && !disableGenerateMipMaps && !texture.isCube) {
            this._bindTextureDirectly(gl.TEXTURE_2D, texture, true);
            gl.generateMipmap(gl.TEXTURE_2D);
            this._bindTextureDirectly(gl.TEXTURE_2D, null);
        }

        if (onBeforeUnbind) {
            if (texture._MSAAFramebuffer) {
                // Bind the correct framebuffer
                this.bindUnboundFramebuffer(texture._framebuffer);
            }
            onBeforeUnbind();
        }

        this.bindUnboundFramebuffer(null);
    }

    /**
     * Unbind a list of render target textures from the webGL context
     * This is used only when drawBuffer extension or webGL2 are active
     * @param textures defines the render target textures to unbind
     * @param disableGenerateMipMaps defines a boolean indicating that mipmaps must not be generated
     * @param onBeforeUnbind defines a function which will be called before the effective unbind
     */
    public unBindMultiColorAttachmentFramebuffer(textures: InternalTexture[], disableGenerateMipMaps = false, onBeforeUnbind?: () => void): void {
        this._currentRenderTarget = null;

        // If MSAA, we need to bitblt back to main texture
        var gl = this._gl;

        if (textures[0]._MSAAFramebuffer) {
            gl.bindFramebuffer(gl.READ_FRAMEBUFFER, textures[0]._MSAAFramebuffer);
            gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, textures[0]._framebuffer);

            var attachments = textures[0]._attachments;
            if (!attachments) {
                attachments = new Array(textures.length);
                textures[0]._attachments = attachments;
            }

            for (var i = 0; i < textures.length; i++) {
                var texture = textures[i];

                for (var j = 0; j < attachments.length; j++) {
                    attachments[j] = gl.NONE;
                }

                attachments[i] = (<any>gl)[this.webGLVersion > 1 ? "COLOR_ATTACHMENT" + i : "COLOR_ATTACHMENT" + i + "_WEBGL"];
                gl.readBuffer(attachments[i]);
                gl.drawBuffers(attachments);
                gl.blitFramebuffer(0, 0, texture.width, texture.height,
                    0, 0, texture.width, texture.height,
                    gl.COLOR_BUFFER_BIT, gl.NEAREST);

            }
            for (var i = 0; i < attachments.length; i++) {
                attachments[i] = (<any>gl)[this.webGLVersion > 1 ? "COLOR_ATTACHMENT" + i : "COLOR_ATTACHMENT" + i + "_WEBGL"];
            }
            gl.drawBuffers(attachments);
        }

        for (var i = 0; i < textures.length; i++) {
            var texture = textures[i];
            if (texture.generateMipMaps && !disableGenerateMipMaps && !texture.isCube) {
                this._bindTextureDirectly(gl.TEXTURE_2D, texture);
                gl.generateMipmap(gl.TEXTURE_2D);
                this._bindTextureDirectly(gl.TEXTURE_2D, null);
            }
        }

        if (onBeforeUnbind) {
            if (textures[0]._MSAAFramebuffer) {
                // Bind the correct framebuffer
                this.bindUnboundFramebuffer(textures[0]._framebuffer);
            }
            onBeforeUnbind();
        }

        this.bindUnboundFramebuffer(null);
    }

    /**
     * Force the mipmap generation for the given render target texture
     * @param texture defines the render target texture to use
     */
    public generateMipMapsForCubemap(texture: InternalTexture) {
        if (texture.generateMipMaps) {
            var gl = this._gl;
            this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, texture, true);
            gl.generateMipmap(gl.TEXTURE_CUBE_MAP);
            this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, null);
        }
    }

    /**
     * Force a webGL flush (ie. a flush of all waiting webGL commands)
     */
    public flushFramebuffer(): void {
        this._gl.flush();
    }

    /**
     * Unbind the current render target and bind the default framebuffer
     */
    public restoreDefaultFramebuffer(): void {
        if (this._currentRenderTarget) {
            this.unBindFramebuffer(this._currentRenderTarget);
        } else {
            this.bindUnboundFramebuffer(null);
        }
        if (this._cachedViewport) {
            this.setViewport(this._cachedViewport);
        }

        this.wipeCaches();
    }

    // UBOs

    /**
     * Create an uniform buffer
     * @see http://doc.babylonjs.com/features/webgl2#uniform-buffer-objets
     * @param elements defines the content of the uniform buffer
     * @returns the webGL uniform buffer
     */
    public createUniformBuffer(elements: FloatArray): WebGLBuffer {
        var ubo = this._gl.createBuffer();

        if (!ubo) {
            throw new Error("Unable to create uniform buffer");
        }

        this.bindUniformBuffer(ubo);

        if (elements instanceof Float32Array) {
            this._gl.bufferData(this._gl.UNIFORM_BUFFER, <Float32Array>elements, this._gl.STATIC_DRAW);
        } else {
            this._gl.bufferData(this._gl.UNIFORM_BUFFER, new Float32Array(<number[]>elements), this._gl.STATIC_DRAW);
        }

        this.bindUniformBuffer(null);

        ubo.references = 1;
        return ubo;
    }

    /**
     * Create a dynamic uniform buffer
     * @see http://doc.babylonjs.com/features/webgl2#uniform-buffer-objets
     * @param elements defines the content of the uniform buffer
     * @returns the webGL uniform buffer
     */
    public createDynamicUniformBuffer(elements: FloatArray): WebGLBuffer {
        var ubo = this._gl.createBuffer();

        if (!ubo) {
            throw new Error("Unable to create dynamic uniform buffer");
        }

        this.bindUniformBuffer(ubo);

        if (elements instanceof Float32Array) {
            this._gl.bufferData(this._gl.UNIFORM_BUFFER, <Float32Array>elements, this._gl.DYNAMIC_DRAW);
        } else {
            this._gl.bufferData(this._gl.UNIFORM_BUFFER, new Float32Array(<number[]>elements), this._gl.DYNAMIC_DRAW);
        }

        this.bindUniformBuffer(null);

        ubo.references = 1;
        return ubo;
    }

    /**
     * Update an existing uniform buffer
     * @see http://doc.babylonjs.com/features/webgl2#uniform-buffer-objets
     * @param uniformBuffer defines the target uniform buffer
     * @param elements defines the content to update
     * @param offset defines the offset in the uniform buffer where update should start
     * @param count defines the size of the data to update
     */
    public updateUniformBuffer(uniformBuffer: WebGLBuffer, elements: FloatArray, offset?: number, count?: number): void {
        this.bindUniformBuffer(uniformBuffer);

        if (offset === undefined) {
            offset = 0;
        }

        if (count === undefined) {
            if (elements instanceof Float32Array) {
                this._gl.bufferSubData(this._gl.UNIFORM_BUFFER, offset, <Float32Array>elements);
            } else {
                this._gl.bufferSubData(this._gl.UNIFORM_BUFFER, offset, new Float32Array(<number[]>elements));
            }
        } else {
            if (elements instanceof Float32Array) {
                this._gl.bufferSubData(this._gl.UNIFORM_BUFFER, 0, <Float32Array>elements.subarray(offset, offset + count));
            } else {
                this._gl.bufferSubData(this._gl.UNIFORM_BUFFER, 0, new Float32Array(<number[]>elements).subarray(offset, offset + count));
            }
        }

        this.bindUniformBuffer(null);
    }

    // VBOs
    private _resetVertexBufferBinding(): void {
        this.bindArrayBuffer(null);
        this._cachedVertexBuffers = null;
    }

    /**
     * Creates a vertex buffer
     * @param data the data for the vertex buffer
     * @returns the new WebGL static buffer
     */
    public createVertexBuffer(data: DataArray): WebGLBuffer {
        var vbo = this._gl.createBuffer();

        if (!vbo) {
            throw new Error("Unable to create vertex buffer");
        }

        this.bindArrayBuffer(vbo);

        if (data instanceof Array) {
            this._gl.bufferData(this._gl.ARRAY_BUFFER, new Float32Array(data), this._gl.STATIC_DRAW);
        } else {
            this._gl.bufferData(this._gl.ARRAY_BUFFER, <ArrayBuffer>data, this._gl.STATIC_DRAW);
        }

        this._resetVertexBufferBinding();
        vbo.references = 1;
        return vbo;
    }

    /**
     * Creates a dynamic vertex buffer
     * @param data the data for the dynamic vertex buffer
     * @returns the new WebGL dynamic buffer
     */
    public createDynamicVertexBuffer(data: DataArray): WebGLBuffer {
        var vbo = this._gl.createBuffer();

        if (!vbo) {
            throw new Error("Unable to create dynamic vertex buffer");
        }

        this.bindArrayBuffer(vbo);

        if (data instanceof Array) {
            this._gl.bufferData(this._gl.ARRAY_BUFFER, new Float32Array(data), this._gl.DYNAMIC_DRAW);
        } else {
            this._gl.bufferData(this._gl.ARRAY_BUFFER, <ArrayBuffer>data, this._gl.DYNAMIC_DRAW);
        }

        this._resetVertexBufferBinding();
        vbo.references = 1;
        return vbo;
    }

    /**
     * Update a dynamic index buffer
     * @param indexBuffer defines the target index buffer
     * @param indices defines the data to update
     * @param offset defines the offset in the target index buffer where update should start
     */
    public updateDynamicIndexBuffer(indexBuffer: WebGLBuffer, indices: IndicesArray, offset: number = 0): void {
        // Force cache update
        this._currentBoundBuffer[this._gl.ELEMENT_ARRAY_BUFFER] = null;
        this.bindIndexBuffer(indexBuffer);
        var arrayBuffer;

        if (indices instanceof Uint16Array || indices instanceof Uint32Array) {
            arrayBuffer = indices;
        } else {
            arrayBuffer = indexBuffer.is32Bits ? new Uint32Array(indices) : new Uint16Array(indices);
        }

        this._gl.bufferData(this._gl.ELEMENT_ARRAY_BUFFER, arrayBuffer, this._gl.DYNAMIC_DRAW);

        this._resetIndexBufferBinding();
    }

    /**
     * Updates a dynamic vertex buffer.
     * @param vertexBuffer the vertex buffer to update
     * @param data the data used to update the vertex buffer
     * @param byteOffset the byte offset of the data
     * @param byteLength the byte length of the data
     */
    public updateDynamicVertexBuffer(vertexBuffer: WebGLBuffer, data: DataArray, byteOffset?: number, byteLength?: number): void {
        this.bindArrayBuffer(vertexBuffer);

        if (byteOffset === undefined) {
            byteOffset = 0;
        }

        if (byteLength === undefined) {
            if (data instanceof Array) {
                this._gl.bufferSubData(this._gl.ARRAY_BUFFER, byteOffset, new Float32Array(data));
            } else {
                this._gl.bufferSubData(this._gl.ARRAY_BUFFER, byteOffset, <ArrayBuffer>data);
            }
        } else {
            if (data instanceof Array) {
                this._gl.bufferSubData(this._gl.ARRAY_BUFFER, 0, new Float32Array(data).subarray(byteOffset, byteOffset + byteLength));
            } else {
                if (data instanceof ArrayBuffer) {
                    data = new Uint8Array(data, byteOffset, byteLength);
                } else {
                    data = new Uint8Array(data.buffer, data.byteOffset + byteOffset, byteLength);
                }

                this._gl.bufferSubData(this._gl.ARRAY_BUFFER, 0, <ArrayBuffer>data);
            }
        }

        this._resetVertexBufferBinding();
    }

    private _resetIndexBufferBinding(): void {
        this.bindIndexBuffer(null);
        this._cachedIndexBuffer = null;
    }

    /**
     * Creates a new index buffer
     * @param indices defines the content of the index buffer
     * @param updatable defines if the index buffer must be updatable
     * @returns a new webGL buffer
     */
    public createIndexBuffer(indices: IndicesArray, updatable?: boolean): WebGLBuffer {
        var vbo = this._gl.createBuffer();

        if (!vbo) {
            throw new Error("Unable to create index buffer");
        }

        this.bindIndexBuffer(vbo);

        // Check for 32 bits indices
        var arrayBuffer;
        var need32Bits = false;

        if (indices instanceof Uint16Array) {
            arrayBuffer = indices;
        } else {
            //check 32 bit support
            if (this._caps.uintIndices) {
                if (indices instanceof Uint32Array) {
                    arrayBuffer = indices;
                    need32Bits = true;
                } else {
                    //number[] or Int32Array, check if 32 bit is necessary
                    for (var index = 0; index < indices.length; index++) {
                        if (indices[index] > 65535) {
                            need32Bits = true;
                            break;
                        }
                    }

                    arrayBuffer = need32Bits ? new Uint32Array(indices) : new Uint16Array(indices);
                }
            } else {
                //no 32 bit support, force conversion to 16 bit (values greater 16 bit are lost)
                arrayBuffer = new Uint16Array(indices);
            }
        }

        this._gl.bufferData(this._gl.ELEMENT_ARRAY_BUFFER, arrayBuffer, updatable ? this._gl.DYNAMIC_DRAW : this._gl.STATIC_DRAW);
        this._resetIndexBufferBinding();
        vbo.references = 1;
        vbo.is32Bits = need32Bits;
        return vbo;
    }

    /**
     * Bind a webGL buffer to the webGL context
     * @param buffer defines the buffer to bind
     */
    public bindArrayBuffer(buffer: Nullable<WebGLBuffer>): void {
        if (!this._vaoRecordInProgress) {
            this._unbindVertexArrayObject();
        }
        this.bindBuffer(buffer, this._gl.ARRAY_BUFFER);
    }

    /**
     * Bind an uniform buffer to the current webGL context
     * @param buffer defines the buffer to bind
     */
    public bindUniformBuffer(buffer: Nullable<WebGLBuffer>): void {
        this._gl.bindBuffer(this._gl.UNIFORM_BUFFER, buffer);
    }

    /**
     * Bind a buffer to the current webGL context at a given location
     * @param buffer defines the buffer to bind
     * @param location defines the index where to bind the buffer
     */
    public bindUniformBufferBase(buffer: WebGLBuffer, location: number): void {
        this._gl.bindBufferBase(this._gl.UNIFORM_BUFFER, location, buffer);
    }

    /**
     * Bind a specific block at a given index in a specific shader program
     * @param shaderProgram defines the shader program
     * @param blockName defines the block name
     * @param index defines the index where to bind the block
     */
    public bindUniformBlock(shaderProgram: WebGLProgram, blockName: string, index: number): void {
        var uniformLocation = this._gl.getUniformBlockIndex(shaderProgram, blockName);

        this._gl.uniformBlockBinding(shaderProgram, uniformLocation, index);
    }

    private bindIndexBuffer(buffer: Nullable<WebGLBuffer>): void {
        if (!this._vaoRecordInProgress) {
            this._unbindVertexArrayObject();
        }
        this.bindBuffer(buffer, this._gl.ELEMENT_ARRAY_BUFFER);
    }

    private bindBuffer(buffer: Nullable<WebGLBuffer>, target: number): void {
        if (this._vaoRecordInProgress || this._currentBoundBuffer[target] !== buffer) {
            this._gl.bindBuffer(target, buffer);
            this._currentBoundBuffer[target] = buffer;
        }
    }

    /**
     * update the bound buffer with the given data
     * @param data defines the data to update
     */
    public updateArrayBuffer(data: Float32Array): void {
        this._gl.bufferSubData(this._gl.ARRAY_BUFFER, 0, data);
    }

    private _vertexAttribPointer(buffer: WebGLBuffer, indx: number, size: number, type: number, normalized: boolean, stride: number, offset: number): void {
        var pointer = this._currentBufferPointers[indx];

        var changed = false;
        if (!pointer.active) {
            changed = true;
            pointer.active = true;
            pointer.index = indx;
            pointer.size = size;
            pointer.type = type;
            pointer.normalized = normalized;
            pointer.stride = stride;
            pointer.offset = offset;
            pointer.buffer = buffer;
        } else {
            if (pointer.buffer !== buffer) { pointer.buffer = buffer; changed = true; }
            if (pointer.size !== size) { pointer.size = size; changed = true; }
            if (pointer.type !== type) { pointer.type = type; changed = true; }
            if (pointer.normalized !== normalized) { pointer.normalized = normalized; changed = true; }
            if (pointer.stride !== stride) { pointer.stride = stride; changed = true; }
            if (pointer.offset !== offset) { pointer.offset = offset; changed = true; }
        }

        if (changed || this._vaoRecordInProgress) {
            this.bindArrayBuffer(buffer);
            this._gl.vertexAttribPointer(indx, size, type, normalized, stride, offset);
        }
    }

    private _bindIndexBufferWithCache(indexBuffer: Nullable<WebGLBuffer>): void {
        if (indexBuffer == null) {
            return;
        }
        if (this._cachedIndexBuffer !== indexBuffer) {
            this._cachedIndexBuffer = indexBuffer;
            this.bindIndexBuffer(indexBuffer);
            this._uintIndicesCurrentlySet = indexBuffer.is32Bits;
        }
    }

    private _bindVertexBuffersAttributes(vertexBuffers: { [key: string]: Nullable<VertexBuffer> }, effect: Effect): void {
        var attributes = effect.getAttributesNames();

        if (!this._vaoRecordInProgress) {
            this._unbindVertexArrayObject();
        }

        this.unbindAllAttributes();

        for (var index = 0; index < attributes.length; index++) {
            var order = effect.getAttributeLocation(index);

            if (order >= 0) {
                var vertexBuffer = vertexBuffers[attributes[index]];

                if (!vertexBuffer) {
                    continue;
                }

                this._gl.enableVertexAttribArray(order);
                if (!this._vaoRecordInProgress) {
                    this._vertexAttribArraysEnabled[order] = true;
                }

                var buffer = vertexBuffer.getBuffer();
                if (buffer) {
                    this._vertexAttribPointer(buffer, order, vertexBuffer.getSize(), vertexBuffer.type, vertexBuffer.normalized, vertexBuffer.byteStride, vertexBuffer.byteOffset);

                    if (vertexBuffer.getIsInstanced()) {
                        this._gl.vertexAttribDivisor(order, vertexBuffer.getInstanceDivisor());
                        if (!this._vaoRecordInProgress) {
                            this._currentInstanceLocations.push(order);
                            this._currentInstanceBuffers.push(buffer);
                        }
                    }
                }
            }
        }
    }

    /**
     * Records a vertex array object
     * @see http://doc.babylonjs.com/features/webgl2#vertex-array-objects
     * @param vertexBuffers defines the list of vertex buffers to store
     * @param indexBuffer defines the index buffer to store
     * @param effect defines the effect to store
     * @returns the new vertex array object
     */
    public recordVertexArrayObject(vertexBuffers: { [key: string]: VertexBuffer; }, indexBuffer: Nullable<WebGLBuffer>, effect: Effect): WebGLVertexArrayObject {
        var vao = this._gl.createVertexArray();

        this._vaoRecordInProgress = true;

        this._gl.bindVertexArray(vao);

        this._mustWipeVertexAttributes = true;
        this._bindVertexBuffersAttributes(vertexBuffers, effect);

        this.bindIndexBuffer(indexBuffer);

        this._vaoRecordInProgress = false;
        this._gl.bindVertexArray(null);

        return vao;
    }

    /**
     * Bind a specific vertex array object
     * @see http://doc.babylonjs.com/features/webgl2#vertex-array-objects
     * @param vertexArrayObject defines the vertex array object to bind
     * @param indexBuffer defines the index buffer to bind
     */
    public bindVertexArrayObject(vertexArrayObject: WebGLVertexArrayObject, indexBuffer: Nullable<WebGLBuffer>): void {
        if (this._cachedVertexArrayObject !== vertexArrayObject) {
            this._cachedVertexArrayObject = vertexArrayObject;

            this._gl.bindVertexArray(vertexArrayObject);
            this._cachedVertexBuffers = null;
            this._cachedIndexBuffer = null;

            this._uintIndicesCurrentlySet = indexBuffer != null && indexBuffer.is32Bits;
            this._mustWipeVertexAttributes = true;
        }
    }

    /**
     * Bind webGl buffers directly to the webGL context
     * @param vertexBuffer defines the vertex buffer to bind
     * @param indexBuffer defines the index buffer to bind
     * @param vertexDeclaration defines the vertex declaration to use with the vertex buffer
     * @param vertexStrideSize defines the vertex stride of the vertex buffer
     * @param effect defines the effect associated with the vertex buffer
     */
    public bindBuffersDirectly(vertexBuffer: WebGLBuffer, indexBuffer: WebGLBuffer, vertexDeclaration: number[], vertexStrideSize: number, effect: Effect): void {
        if (this._cachedVertexBuffers !== vertexBuffer || this._cachedEffectForVertexBuffers !== effect) {
            this._cachedVertexBuffers = vertexBuffer;
            this._cachedEffectForVertexBuffers = effect;

            let attributesCount = effect.getAttributesCount();

            this._unbindVertexArrayObject();
            this.unbindAllAttributes();

            var offset = 0;
            for (var index = 0; index < attributesCount; index++) {

                if (index < vertexDeclaration.length) {

                    var order = effect.getAttributeLocation(index);

                    if (order >= 0) {
                        this._gl.enableVertexAttribArray(order);
                        this._vertexAttribArraysEnabled[order] = true;
                        this._vertexAttribPointer(vertexBuffer, order, vertexDeclaration[index], this._gl.FLOAT, false, vertexStrideSize, offset);
                    }

                    offset += vertexDeclaration[index] * 4;
                }
            }
        }

        this._bindIndexBufferWithCache(indexBuffer);
    }

    private _unbindVertexArrayObject(): void {
        if (!this._cachedVertexArrayObject) {
            return;
        }

        this._cachedVertexArrayObject = null;
        this._gl.bindVertexArray(null);
    }

    /**
     * Bind a list of vertex buffers to the webGL context
     * @param vertexBuffers defines the list of vertex buffers to bind
     * @param indexBuffer defines the index buffer to bind
     * @param effect defines the effect associated with the vertex buffers
     */
    public bindBuffers(vertexBuffers: { [key: string]: Nullable<VertexBuffer> }, indexBuffer: Nullable<WebGLBuffer>, effect: Effect): void {
        if (this._cachedVertexBuffers !== vertexBuffers || this._cachedEffectForVertexBuffers !== effect) {
            this._cachedVertexBuffers = vertexBuffers;
            this._cachedEffectForVertexBuffers = effect;

            this._bindVertexBuffersAttributes(vertexBuffers, effect);
        }

        this._bindIndexBufferWithCache(indexBuffer);
    }

    /**
     * Unbind all instance attributes
     */
    public unbindInstanceAttributes() {
        var boundBuffer;
        for (var i = 0, ul = this._currentInstanceLocations.length; i < ul; i++) {
            var instancesBuffer = this._currentInstanceBuffers[i];
            if (boundBuffer != instancesBuffer && instancesBuffer.references) {
                boundBuffer = instancesBuffer;
                this.bindArrayBuffer(instancesBuffer);
            }
            var offsetLocation = this._currentInstanceLocations[i];
            this._gl.vertexAttribDivisor(offsetLocation, 0);
        }
        this._currentInstanceBuffers.length = 0;
        this._currentInstanceLocations.length = 0;
    }

    /**
     * Release and free the memory of a vertex array object
     * @param vao defines the vertex array object to delete
     */
    public releaseVertexArrayObject(vao: WebGLVertexArrayObject) {
        this._gl.deleteVertexArray(vao);
    }

    /** @hidden */
    public _releaseBuffer(buffer: WebGLBuffer): boolean {
        buffer.references--;

        if (buffer.references === 0) {
            this._gl.deleteBuffer(buffer);
            return true;
        }

        return false;
    }

    /**
     * Creates a webGL buffer to use with instanciation
     * @param capacity defines the size of the buffer
     * @returns the webGL buffer
     */
    public createInstancesBuffer(capacity: number): WebGLBuffer {
        var buffer = this._gl.createBuffer();

        if (!buffer) {
            throw new Error("Unable to create instance buffer");
        }

        buffer.capacity = capacity;

        this.bindArrayBuffer(buffer);
        this._gl.bufferData(this._gl.ARRAY_BUFFER, capacity, this._gl.DYNAMIC_DRAW);
        return buffer;
    }

    /**
     * Delete a webGL buffer used with instanciation
     * @param buffer defines the webGL buffer to delete
     */
    public deleteInstancesBuffer(buffer: WebGLBuffer): void {
        this._gl.deleteBuffer(buffer);
    }

    /**
     * Update the content of a webGL buffer used with instanciation and bind it to the webGL context
     * @param instancesBuffer defines the webGL buffer to update and bind
     * @param data defines the data to store in the buffer
     * @param offsetLocations defines the offsets or attributes information used to determine where data must be stored in the buffer
     */
    public updateAndBindInstancesBuffer(instancesBuffer: WebGLBuffer, data: Float32Array, offsetLocations: number[] | InstancingAttributeInfo[]): void {
        this.bindArrayBuffer(instancesBuffer);
        if (data) {
            this._gl.bufferSubData(this._gl.ARRAY_BUFFER, 0, data);
        }

        if ((<any>offsetLocations[0]).index !== undefined) {
            let stride = 0;
            for (let i = 0; i < offsetLocations.length; i++) {
                let ai = <InstancingAttributeInfo>offsetLocations[i];
                stride += ai.attributeSize * 4;
            }
            for (let i = 0; i < offsetLocations.length; i++) {
                let ai = <InstancingAttributeInfo>offsetLocations[i];

                if (!this._vertexAttribArraysEnabled[ai.index]) {
                    this._gl.enableVertexAttribArray(ai.index);
                    this._vertexAttribArraysEnabled[ai.index] = true;
                }

                this._vertexAttribPointer(instancesBuffer, ai.index, ai.attributeSize, ai.attribyteType || this._gl.FLOAT, ai.normalized || false, stride, ai.offset);
                this._gl.vertexAttribDivisor(ai.index, 1);
                this._currentInstanceLocations.push(ai.index);
                this._currentInstanceBuffers.push(instancesBuffer);
            }
        } else {
            for (let index = 0; index < 4; index++) {
                let offsetLocation = <number>offsetLocations[index];

                if (!this._vertexAttribArraysEnabled[offsetLocation]) {
                    this._gl.enableVertexAttribArray(offsetLocation);
                    this._vertexAttribArraysEnabled[offsetLocation] = true;
                }

                this._vertexAttribPointer(instancesBuffer, offsetLocation, 4, this._gl.FLOAT, false, 64, index * 16);
                this._gl.vertexAttribDivisor(offsetLocation, 1);
                this._currentInstanceLocations.push(offsetLocation);
                this._currentInstanceBuffers.push(instancesBuffer);
            }
        }
    }

    /**
     * Apply all cached states (depth, culling, stencil and alpha)
     */
    public applyStates() {
        this._depthCullingState.apply(this._gl);
        this._stencilState.apply(this._gl);
        this._alphaState.apply(this._gl);
    }

    /**
     * Send a draw order
     * @param useTriangles defines if triangles must be used to draw (else wireframe will be used)
     * @param indexStart defines the starting index
     * @param indexCount defines the number of index to draw
     * @param instancesCount defines the number of instances to draw (if instanciation is enabled)
     */
    public draw(useTriangles: boolean, indexStart: number, indexCount: number, instancesCount?: number): void {
        this.drawElementsType(useTriangles ? Material.TriangleFillMode : Material.WireFrameFillMode, indexStart, indexCount, instancesCount);
    }

    /**
     * Draw a list of points
     * @param verticesStart defines the index of first vertex to draw
     * @param verticesCount defines the count of vertices to draw
     * @param instancesCount defines the number of instances to draw (if instanciation is enabled)
     */
    public drawPointClouds(verticesStart: number, verticesCount: number, instancesCount?: number): void {
        this.drawArraysType(Material.PointFillMode, verticesStart, verticesCount, instancesCount);
    }

    /**
     * Draw a list of unindexed primitives
     * @param useTriangles defines if triangles must be used to draw (else wireframe will be used)
     * @param verticesStart defines the index of first vertex to draw
     * @param verticesCount defines the count of vertices to draw
     * @param instancesCount defines the number of instances to draw (if instanciation is enabled)
     */
    public drawUnIndexed(useTriangles: boolean, verticesStart: number, verticesCount: number, instancesCount?: number): void {
        this.drawArraysType(useTriangles ? Material.TriangleFillMode : Material.WireFrameFillMode, verticesStart, verticesCount, instancesCount);
    }

    /**
     * Draw a list of indexed primitives
     * @param fillMode defines the primitive to use
     * @param indexStart defines the starting index
     * @param indexCount defines the number of index to draw
     * @param instancesCount defines the number of instances to draw (if instanciation is enabled)
     */
    public drawElementsType(fillMode: number, indexStart: number, indexCount: number, instancesCount?: number): void {
        // Apply states
        this.applyStates();

        this._drawCalls.addCount(1, false);
        // Render

        const drawMode = this._drawMode(fillMode);
        var indexFormat = this._uintIndicesCurrentlySet ? this._gl.UNSIGNED_INT : this._gl.UNSIGNED_SHORT;
        var mult = this._uintIndicesCurrentlySet ? 4 : 2;
        if (instancesCount) {
            this._gl.drawElementsInstanced(drawMode, indexCount, indexFormat, indexStart * mult, instancesCount);
        } else {
            this._gl.drawElements(drawMode, indexCount, indexFormat, indexStart * mult);
        }
    }

    /**
     * Draw a list of unindexed primitives
     * @param fillMode defines the primitive to use
     * @param verticesStart defines the index of first vertex to draw
     * @param verticesCount defines the count of vertices to draw
     * @param instancesCount defines the number of instances to draw (if instanciation is enabled)
     */
    public drawArraysType(fillMode: number, verticesStart: number, verticesCount: number, instancesCount?: number): void {
        // Apply states
        this.applyStates();
        this._drawCalls.addCount(1, false);

        const drawMode = this._drawMode(fillMode);
        if (instancesCount) {
            this._gl.drawArraysInstanced(drawMode, verticesStart, verticesCount, instancesCount);
        } else {
            this._gl.drawArrays(drawMode, verticesStart, verticesCount);
        }
    }

    private _drawMode(fillMode: number): number {
        switch (fillMode) {
            // Triangle views
            case Material.TriangleFillMode:
                return this._gl.TRIANGLES;
            case Material.PointFillMode:
                return this._gl.POINTS;
            case Material.WireFrameFillMode:
                return this._gl.LINES;
            // Draw modes
            case Material.PointListDrawMode:
                return this._gl.POINTS;
            case Material.LineListDrawMode:
                return this._gl.LINES;
            case Material.LineLoopDrawMode:
                return this._gl.LINE_LOOP;
            case Material.LineStripDrawMode:
                return this._gl.LINE_STRIP;
            case Material.TriangleStripDrawMode:
                return this._gl.TRIANGLE_STRIP;
            case Material.TriangleFanDrawMode:
                return this._gl.TRIANGLE_FAN;
            default:
                return this._gl.TRIANGLES;
        }
    }

    // Shaders

    /** @hidden */
    public _releaseEffect(effect: Effect): void {
        if (this._compiledEffects[effect._key]) {
            delete this._compiledEffects[effect._key];

            this._deleteProgram(effect.getProgram());
        }
    }

    /** @hidden */
    public _deleteProgram(program: WebGLProgram): void {
        if (program) {
            program.__SPECTOR_rebuildProgram = null;

            if (program.transformFeedback) {
                this.deleteTransformFeedback(program.transformFeedback);
                program.transformFeedback = null;
            }

            this._gl.deleteProgram(program);
        }
    }

    /**
     * Create a new effect (used to store vertex/fragment shaders)
     * @param baseName defines the base name of the effect (The name of file without .fragment.fx or .vertex.fx)
     * @param attributesNamesOrOptions defines either a list of attribute names or an EffectCreationOptions object
     * @param uniformsNamesOrEngine defines either a list of uniform names or the engine to use
     * @param samplers defines an array of string used to represent textures
     * @param defines defines the string containing the defines to use to compile the shaders
     * @param fallbacks defines the list of potential fallbacks to use if shader conmpilation fails
     * @param onCompiled defines a function to call when the effect creation is successful
     * @param onError defines a function to call when the effect creation has failed
     * @param indexParameters defines an object containing the index values to use to compile shaders (like the maximum number of simultaneous lights)
     * @returns the new Effect
     */
    public createEffect(baseName: any, attributesNamesOrOptions: string[] | EffectCreationOptions, uniformsNamesOrEngine: string[] | Engine, samplers?: string[], defines?: string, fallbacks?: EffectFallbacks,
        onCompiled?: (effect: Effect) => void, onError?: (effect: Effect, errors: string) => void, indexParameters?: any): Effect {
        var vertex = baseName.vertexElement || baseName.vertex || baseName;
        var fragment = baseName.fragmentElement || baseName.fragment || baseName;

        var name = vertex + "+" + fragment + "@" + (defines ? defines : (<EffectCreationOptions>attributesNamesOrOptions).defines);
        if (this._compiledEffects[name]) {
            var compiledEffect = <Effect>this._compiledEffects[name];
            if (onCompiled && compiledEffect.isReady()) {
                onCompiled(compiledEffect);
            }

            return compiledEffect;
        }
        var effect = new Effect(baseName, attributesNamesOrOptions, uniformsNamesOrEngine, samplers, this, defines, fallbacks, onCompiled, onError, indexParameters);
        effect._key = name;
        this._compiledEffects[name] = effect;

        return effect;
    }

    private _compileShader(source: string, type: string, defines: Nullable<string>, shaderVersion: string): WebGLShader {
        return this._compileRawShader(shaderVersion + (defines ? defines + "\n" : "") + source, type);
    }

    private _compileRawShader(source: string, type: string): WebGLShader {
        var gl = this._gl;
        var shader = gl.createShader(type === "vertex" ? gl.VERTEX_SHADER : gl.FRAGMENT_SHADER);

        if (!shader) {
            throw new Error("Something went wrong while compile the shader.");
        }

        gl.shaderSource(shader, source);
        gl.compileShader(shader);

        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            let log = gl.getShaderInfoLog(shader);
            if (log) {
                throw new Error(log);
            }
        }

        return shader;
    }

    /**
     * Directly creates a webGL program
     * @param vertexCode defines the vertex shader code to use
     * @param fragmentCode defines the fragment shader code to use
     * @param context defines the webGL context to use (if not set, the current one will be used)
     * @param transformFeedbackVaryings defines the list of transform feedback varyings to use
     * @returns the new webGL program
     */
    public createRawShaderProgram(vertexCode: string, fragmentCode: string, context?: WebGLRenderingContext, transformFeedbackVaryings: Nullable<string[]> = null): WebGLProgram {
        context = context || this._gl;

        var vertexShader = this._compileRawShader(vertexCode, "vertex");
        var fragmentShader = this._compileRawShader(fragmentCode, "fragment");

        return this._createShaderProgram(vertexShader, fragmentShader, context, transformFeedbackVaryings);
    }

    /**
     * Creates a webGL program
     * @param vertexCode  defines the vertex shader code to use
     * @param fragmentCode defines the fragment shader code to use
     * @param defines defines the string containing the defines to use to compile the shaders
     * @param context defines the webGL context to use (if not set, the current one will be used)
     * @param transformFeedbackVaryings defines the list of transform feedback varyings to use
     * @returns the new webGL program
     */
    public createShaderProgram(vertexCode: string, fragmentCode: string, defines: Nullable<string>, context?: WebGLRenderingContext, transformFeedbackVaryings: Nullable<string[]> = null): WebGLProgram {
        context = context || this._gl;

        this.onBeforeShaderCompilationObservable.notifyObservers(this);

        var shaderVersion = (this._webGLVersion > 1) ? "#version 300 es\n#define WEBGL2 \n" : "";
        var vertexShader = this._compileShader(vertexCode, "vertex", defines, shaderVersion);
        var fragmentShader = this._compileShader(fragmentCode, "fragment", defines, shaderVersion);

        let program = this._createShaderProgram(vertexShader, fragmentShader, context, transformFeedbackVaryings);

        this.onAfterShaderCompilationObservable.notifyObservers(this);

        return program;
    }

    private _createShaderProgram(vertexShader: WebGLShader, fragmentShader: WebGLShader, context: WebGLRenderingContext, transformFeedbackVaryings: Nullable<string[]> = null): WebGLProgram {
        var shaderProgram = context.createProgram();

        if (!shaderProgram) {
            throw new Error("Unable to create program");
        }

        context.attachShader(shaderProgram, vertexShader);
        context.attachShader(shaderProgram, fragmentShader);

        if (this.webGLVersion > 1 && transformFeedbackVaryings) {
            let transformFeedback = this.createTransformFeedback();

            this.bindTransformFeedback(transformFeedback);
            this.setTranformFeedbackVaryings(shaderProgram, transformFeedbackVaryings);
            shaderProgram.transformFeedback = transformFeedback;
        }

        context.linkProgram(shaderProgram);

        if (this.webGLVersion > 1 && transformFeedbackVaryings) {
            this.bindTransformFeedback(null);
        }

        shaderProgram.context = context;
        shaderProgram.vertexShader = vertexShader;
        shaderProgram.fragmentShader = fragmentShader;

        if (!this._caps.parallelShaderCompile) {
            this._finalizeProgram(shaderProgram);
        } else {
            shaderProgram.isParallelCompiled = true;
        }

        return shaderProgram;
    }

    private _finalizeProgram(shaderProgram: WebGLProgram) {
        const context = shaderProgram.context!;
        const vertexShader = shaderProgram.vertexShader!;
        const fragmentShader = shaderProgram.fragmentShader!;

        var linked = context.getProgramParameter(shaderProgram, context.LINK_STATUS);

        if (!linked) {
            var error = context.getProgramInfoLog(shaderProgram);
            if (error) {
                throw new Error(error);
            }
        }

        if (this.validateShaderPrograms) {
            context.validateProgram(shaderProgram);
            var validated = context.getProgramParameter(shaderProgram, context.VALIDATE_STATUS);

            if (!validated) {
                var error = context.getProgramInfoLog(shaderProgram);
                if (error) {
                    throw new Error(error);
                }
            }
        }

        context.deleteShader(vertexShader);
        context.deleteShader(fragmentShader);

        shaderProgram.context = undefined;
        shaderProgram.vertexShader = undefined;
        shaderProgram.fragmentShader = undefined;

        if (shaderProgram.onCompiled) {
            shaderProgram.onCompiled();
            shaderProgram.onCompiled = undefined;
        }
    }

    /** @hidden */
    public _isProgramCompiled(shaderProgram: WebGLProgram): boolean {
        if (!shaderProgram.isParallelCompiled) {
            return true;
        }

        if (this._gl.getProgramParameter(shaderProgram, this._caps.parallelShaderCompile.COMPLETION_STATUS_KHR)) {
            this._finalizeProgram(shaderProgram);
            return true;
        }

        return false;
    }

    /** @hidden */
    public _executeWhenProgramIsCompiled(shaderProgram: WebGLProgram, action: () => void) {
        if (!shaderProgram.isParallelCompiled) {
            action();
            return;
        }

        shaderProgram.onCompiled = action;
    }

    /**
     * Gets the list of webGL uniform locations associated with a specific program based on a list of uniform names
     * @param shaderProgram defines the webGL program to use
     * @param uniformsNames defines the list of uniform names
     * @returns an array of webGL uniform locations
     */
    public getUniforms(shaderProgram: WebGLProgram, uniformsNames: string[]): Nullable<WebGLUniformLocation>[] {
        var results = new Array<Nullable<WebGLUniformLocation>>();

        for (var index = 0; index < uniformsNames.length; index++) {
            results.push(this._gl.getUniformLocation(shaderProgram, uniformsNames[index]));
        }

        return results;
    }

    /**
     * Gets the lsit of active attributes for a given webGL program
     * @param shaderProgram defines the webGL program to use
     * @param attributesNames defines the list of attribute names to get
     * @returns an array of indices indicating the offset of each attribute
     */
    public getAttributes(shaderProgram: WebGLProgram, attributesNames: string[]): number[] {
        var results = [];

        for (var index = 0; index < attributesNames.length; index++) {
            try {
                results.push(this._gl.getAttribLocation(shaderProgram, attributesNames[index]));
            } catch (e) {
                results.push(-1);
            }
        }

        return results;
    }

    /**
     * Activates an effect, mkaing it the current one (ie. the one used for rendering)
     * @param effect defines the effect to activate
     */
    public enableEffect(effect: Nullable<Effect>): void {
        if (!effect || effect === this._currentEffect) {
            return;
        }

        // Use program
        this.bindSamplers(effect);

        this._currentEffect = effect;

        if (effect.onBind) {
            effect.onBind(effect);
        }
        if (effect._onBindObservable) {
            effect._onBindObservable.notifyObservers(effect);
        }
    }

    /**
     * Set the value of an uniform to an array of int32
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of int32 to store
     */
    public setIntArray(uniform: Nullable<WebGLUniformLocation>, array: Int32Array): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform1iv(uniform, array);
    }

    /**
     * Set the value of an uniform to an array of int32 (stored as vec2)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of int32 to store
     */
    public setIntArray2(uniform: Nullable<WebGLUniformLocation>, array: Int32Array): void {
        if (!uniform || array.length % 2 !== 0) {
            return;
        }

        this._gl.uniform2iv(uniform, array);
    }

    /**
     * Set the value of an uniform to an array of int32 (stored as vec3)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of int32 to store
     */
    public setIntArray3(uniform: Nullable<WebGLUniformLocation>, array: Int32Array): void {
        if (!uniform || array.length % 3 !== 0) {
            return;
        }

        this._gl.uniform3iv(uniform, array);
    }

    /**
     * Set the value of an uniform to an array of int32 (stored as vec4)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of int32 to store
     */
    public setIntArray4(uniform: Nullable<WebGLUniformLocation>, array: Int32Array): void {
        if (!uniform || array.length % 4 !== 0) {
            return;
        }

        this._gl.uniform4iv(uniform, array);
    }

    /**
     * Set the value of an uniform to an array of float32
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of float32 to store
     */
    public setFloatArray(uniform: Nullable<WebGLUniformLocation>, array: Float32Array): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform1fv(uniform, array);
    }

    /**
     * Set the value of an uniform to an array of float32 (stored as vec2)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of float32 to store
     */
    public setFloatArray2(uniform: Nullable<WebGLUniformLocation>, array: Float32Array): void {
        if (!uniform || array.length % 2 !== 0) {
            return;
        }

        this._gl.uniform2fv(uniform, array);
    }

    /**
     * Set the value of an uniform to an array of float32 (stored as vec3)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of float32 to store
     */
    public setFloatArray3(uniform: Nullable<WebGLUniformLocation>, array: Float32Array): void {
        if (!uniform || array.length % 3 !== 0) {
            return;
        }

        this._gl.uniform3fv(uniform, array);
    }

    /**
     * Set the value of an uniform to an array of float32 (stored as vec4)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of float32 to store
     */
    public setFloatArray4(uniform: Nullable<WebGLUniformLocation>, array: Float32Array): void {
        if (!uniform || array.length % 4 !== 0) {
            return;
        }

        this._gl.uniform4fv(uniform, array);
    }

    /**
     * Set the value of an uniform to an array of number
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of number to store
     */
    public setArray(uniform: Nullable<WebGLUniformLocation>, array: number[]): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform1fv(uniform, <any>array);
    }

    /**
     * Set the value of an uniform to an array of number (stored as vec2)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of number to store
     */
    public setArray2(uniform: Nullable<WebGLUniformLocation>, array: number[]): void {
        if (!uniform || array.length % 2 !== 0) {
            return;
        }

        this._gl.uniform2fv(uniform, <any>array);
    }

    /**
     * Set the value of an uniform to an array of number (stored as vec3)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of number to store
     */
    public setArray3(uniform: Nullable<WebGLUniformLocation>, array: number[]): void {
        if (!uniform || array.length % 3 !== 0) {
            return;
        }

        this._gl.uniform3fv(uniform, <any>array);
    }

    /**
     * Set the value of an uniform to an array of number (stored as vec4)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of number to store
     */
    public setArray4(uniform: Nullable<WebGLUniformLocation>, array: number[]): void {
        if (!uniform || array.length % 4 !== 0) {
            return;
        }

        this._gl.uniform4fv(uniform, <any>array);
    }

    /**
     * Set the value of an uniform to an array of float32 (stored as matrices)
     * @param uniform defines the webGL uniform location where to store the value
     * @param matrices defines the array of float32 to store
     */
    public setMatrices(uniform: Nullable<WebGLUniformLocation>, matrices: Float32Array): void {
        if (!uniform) {
            return;
        }

        this._gl.uniformMatrix4fv(uniform, false, matrices);
    }

    /**
     * Set the value of an uniform to a matrix
     * @param uniform defines the webGL uniform location where to store the value
     * @param matrix defines the matrix to store
     */
    public setMatrix(uniform: Nullable<WebGLUniformLocation>, matrix: Matrix): void {
        if (!uniform) {
            return;
        }

        this._gl.uniformMatrix4fv(uniform, false, matrix.toArray() as Float32Array);
    }

    /**
     * Set the value of an uniform to a matrix (3x3)
     * @param uniform defines the webGL uniform location where to store the value
     * @param matrix defines the Float32Array representing the 3x3 matrix to store
     */
    public setMatrix3x3(uniform: Nullable<WebGLUniformLocation>, matrix: Float32Array): void {
        if (!uniform) {
            return;
        }

        this._gl.uniformMatrix3fv(uniform, false, matrix);
    }

    /**
     * Set the value of an uniform to a matrix (2x2)
     * @param uniform defines the webGL uniform location where to store the value
     * @param matrix defines the Float32Array representing the 2x2 matrix to store
     */
    public setMatrix2x2(uniform: Nullable<WebGLUniformLocation>, matrix: Float32Array): void {
        if (!uniform) {
            return;
        }

        this._gl.uniformMatrix2fv(uniform, false, matrix);
    }

    /**
     * Set the value of an uniform to a number (int)
     * @param uniform defines the webGL uniform location where to store the value
     * @param value defines the int number to store
     */
    public setInt(uniform: Nullable<WebGLUniformLocation>, value: number): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform1i(uniform, value);
    }

    /**
     * Set the value of an uniform to a number (float)
     * @param uniform defines the webGL uniform location where to store the value
     * @param value defines the float number to store
     */
    public setFloat(uniform: Nullable<WebGLUniformLocation>, value: number): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform1f(uniform, value);
    }

    /**
     * Set the value of an uniform to a vec2
     * @param uniform defines the webGL uniform location where to store the value
     * @param x defines the 1st component of the value
     * @param y defines the 2nd component of the value
     */
    public setFloat2(uniform: Nullable<WebGLUniformLocation>, x: number, y: number): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform2f(uniform, x, y);
    }

    /**
     * Set the value of an uniform to a vec3
     * @param uniform defines the webGL uniform location where to store the value
     * @param x defines the 1st component of the value
     * @param y defines the 2nd component of the value
     * @param z defines the 3rd component of the value
     */
    public setFloat3(uniform: Nullable<WebGLUniformLocation>, x: number, y: number, z: number): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform3f(uniform, x, y, z);
    }

    /**
     * Set the value of an uniform to a boolean
     * @param uniform defines the webGL uniform location where to store the value
     * @param bool defines the boolean to store
     */
    public setBool(uniform: Nullable<WebGLUniformLocation>, bool: number): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform1i(uniform, bool);
    }

    /**
     * Set the value of an uniform to a vec4
     * @param uniform defines the webGL uniform location where to store the value
     * @param x defines the 1st component of the value
     * @param y defines the 2nd component of the value
     * @param z defines the 3rd component of the value
     * @param w defines the 4th component of the value
     */
    public setFloat4(uniform: Nullable<WebGLUniformLocation>, x: number, y: number, z: number, w: number): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform4f(uniform, x, y, z, w);
    }

    /**
     * Set the value of an uniform to a Color3
     * @param uniform defines the webGL uniform location where to store the value
     * @param color3 defines the color to store
     */
    public setColor3(uniform: Nullable<WebGLUniformLocation>, color3: Color3): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform3f(uniform, color3.r, color3.g, color3.b);
    }

    /**
     * Set the value of an uniform to a Color3 and an alpha value
     * @param uniform defines the webGL uniform location where to store the value
     * @param color3 defines the color to store
     * @param alpha defines the alpha component to store
     */
    public setColor4(uniform: Nullable<WebGLUniformLocation>, color3: Color3, alpha: number): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform4f(uniform, color3.r, color3.g, color3.b, alpha);
    }

    /**
     * Sets a Color4 on a uniform variable
     * @param uniform defines the uniform location
     * @param color4 defines the value to be set
     */
    public setDirectColor4(uniform: Nullable<WebGLUniformLocation>, color4: Color4): void {
        if (!uniform) {
            return;
        }

        this._gl.uniform4f(uniform, color4.r, color4.g, color4.b, color4.a);
    }

    // States

    /**
     * Set various states to the webGL context
     * @param culling defines backface culling state
     * @param zOffset defines the value to apply to zOffset (0 by default)
     * @param force defines if states must be applied even if cache is up to date
     * @param reverseSide defines if culling must be reversed (CCW instead of CW and CW instead of CCW)
     */
    public setState(culling: boolean, zOffset: number = 0, force?: boolean, reverseSide = false): void {
        // Culling
        if (this._depthCullingState.cull !== culling || force) {
            this._depthCullingState.cull = culling;
        }

        // Cull face
        var cullFace = this.cullBackFaces ? this._gl.BACK : this._gl.FRONT;
        if (this._depthCullingState.cullFace !== cullFace || force) {
            this._depthCullingState.cullFace = cullFace;
        }

        // Z offset
        this.setZOffset(zOffset);

        // Front face
        var frontFace = reverseSide ? this._gl.CW : this._gl.CCW;
        if (this._depthCullingState.frontFace !== frontFace || force) {
            this._depthCullingState.frontFace = frontFace;
        }
    }

    /**
     * Set the z offset to apply to current rendering
     * @param value defines the offset to apply
     */
    public setZOffset(value: number): void {
        this._depthCullingState.zOffset = value;
    }

    /**
     * Gets the current value of the zOffset
     * @returns the current zOffset state
     */
    public getZOffset(): number {
        return this._depthCullingState.zOffset;
    }

    /**
     * Enable or disable depth buffering
     * @param enable defines the state to set
     */
    public setDepthBuffer(enable: boolean): void {
        this._depthCullingState.depthTest = enable;
    }

    /**
     * Gets a boolean indicating if depth writing is enabled
     * @returns the current depth writing state
     */
    public getDepthWrite(): boolean {
        return this._depthCullingState.depthMask;
    }

    /**
     * Enable or disable depth writing
     * @param enable defines the state to set
     */
    public setDepthWrite(enable: boolean): void {
        this._depthCullingState.depthMask = enable;
    }

    /**
     * Enable or disable color writing
     * @param enable defines the state to set
     */
    public setColorWrite(enable: boolean): void {
        this._gl.colorMask(enable, enable, enable, enable);
        this._colorWrite = enable;
    }

    /**
     * Gets a boolean indicating if color writing is enabled
     * @returns the current color writing state
     */
    public getColorWrite(): boolean {
        return this._colorWrite;
    }

    /**
     * Sets alpha constants used by some alpha blending modes
     * @param r defines the red component
     * @param g defines the green component
     * @param b defines the blue component
     * @param a defines the alpha component
     */
    public setAlphaConstants(r: number, g: number, b: number, a: number) {
        this._alphaState.setAlphaBlendConstants(r, g, b, a);
    }

    /**
     * Sets the current alpha mode
     * @param mode defines the mode to use (one of the Engine.ALPHA_XXX)
     * @param noDepthWriteChange defines if depth writing state should remains unchanged (false by default)
     * @see http://doc.babylonjs.com/resources/transparency_and_how_meshes_are_rendered
     */
    public setAlphaMode(mode: number, noDepthWriteChange: boolean = false): void {
        if (this._alphaMode === mode) {
            return;
        }

        switch (mode) {
            case Engine.ALPHA_DISABLE:
                this._alphaState.alphaBlend = false;
                break;
            case Engine.ALPHA_PREMULTIPLIED:
                this._alphaState.setAlphaBlendFunctionParameters(this._gl.ONE, this._gl.ONE_MINUS_SRC_ALPHA, this._gl.ONE, this._gl.ONE);
                this._alphaState.alphaBlend = true;
                break;
            case Engine.ALPHA_PREMULTIPLIED_PORTERDUFF:
                this._alphaState.setAlphaBlendFunctionParameters(this._gl.ONE, this._gl.ONE_MINUS_SRC_ALPHA, this._gl.ONE, this._gl.ONE_MINUS_SRC_ALPHA);
                this._alphaState.alphaBlend = true;
                break;
            case Engine.ALPHA_COMBINE:
                this._alphaState.setAlphaBlendFunctionParameters(this._gl.SRC_ALPHA, this._gl.ONE_MINUS_SRC_ALPHA, this._gl.ONE, this._gl.ONE);
                this._alphaState.alphaBlend = true;
                break;
            case Engine.ALPHA_ONEONE:
                this._alphaState.setAlphaBlendFunctionParameters(this._gl.ONE, this._gl.ONE, this._gl.ZERO, this._gl.ONE);
                this._alphaState.alphaBlend = true;
                break;
            case Engine.ALPHA_ADD:
                this._alphaState.setAlphaBlendFunctionParameters(this._gl.SRC_ALPHA, this._gl.ONE, this._gl.ZERO, this._gl.ONE);
                this._alphaState.alphaBlend = true;
                break;
            case Engine.ALPHA_SUBTRACT:
                this._alphaState.setAlphaBlendFunctionParameters(this._gl.ZERO, this._gl.ONE_MINUS_SRC_COLOR, this._gl.ONE, this._gl.ONE);
                this._alphaState.alphaBlend = true;
                break;
            case Engine.ALPHA_MULTIPLY:
                this._alphaState.setAlphaBlendFunctionParameters(this._gl.DST_COLOR, this._gl.ZERO, this._gl.ONE, this._gl.ONE);
                this._alphaState.alphaBlend = true;
                break;
            case Engine.ALPHA_MAXIMIZED:
                this._alphaState.setAlphaBlendFunctionParameters(this._gl.SRC_ALPHA, this._gl.ONE_MINUS_SRC_COLOR, this._gl.ONE, this._gl.ONE);
                this._alphaState.alphaBlend = true;
                break;
            case Engine.ALPHA_INTERPOLATE:
                this._alphaState.setAlphaBlendFunctionParameters(this._gl.CONSTANT_COLOR, this._gl.ONE_MINUS_CONSTANT_COLOR, this._gl.CONSTANT_ALPHA, this._gl.ONE_MINUS_CONSTANT_ALPHA);
                this._alphaState.alphaBlend = true;
                break;
            case Engine.ALPHA_SCREENMODE:
                this._alphaState.setAlphaBlendFunctionParameters(this._gl.ONE, this._gl.ONE_MINUS_SRC_COLOR, this._gl.ONE, this._gl.ONE_MINUS_SRC_ALPHA);
                this._alphaState.alphaBlend = true;
                break;
        }
        if (!noDepthWriteChange) {
            this.setDepthWrite(mode === Engine.ALPHA_DISABLE);
        }
        this._alphaMode = mode;
    }

    /**
     * Gets the current alpha mode
     * @see http://doc.babylonjs.com/resources/transparency_and_how_meshes_are_rendered
     * @returns the current alpha mode
     */
    public getAlphaMode(): number {
        return this._alphaMode;
    }

    // Textures

    /**
     * Clears the list of texture accessible through engine.
     * This can help preventing texture load conflict due to name collision.
     */
    public clearInternalTexturesCache() {
        this._internalTexturesCache = [];
    }

    /**
     * Force the entire cache to be cleared
     * You should not have to use this function unless your engine needs to share the webGL context with another engine
     * @param bruteForce defines a boolean to force clearing ALL caches (including stencil, detoh and alpha states)
     */
    public wipeCaches(bruteForce?: boolean): void {
        if (this.preventCacheWipeBetweenFrames && !bruteForce) {
            return;
        }
        this._currentEffect = null;
        this._viewportCached.x = 0;
        this._viewportCached.y = 0;
        this._viewportCached.z = 0;
        this._viewportCached.w = 0;

        if (bruteForce) {
            this.resetTextureCache();
            this._currentProgram = null;

            this._stencilState.reset();
            this._depthCullingState.reset();
            this.setDepthFunctionToLessOrEqual();
            this._alphaState.reset();

            this._unpackFlipYCached = null;
        }

        this._resetVertexBufferBinding();
        this._cachedIndexBuffer = null;
        this._cachedEffectForVertexBuffers = null;
        this._unbindVertexArrayObject();
        this.bindIndexBuffer(null);
    }

    /**
     * Set the compressed texture format to use, based on the formats you have, and the formats
     * supported by the hardware / browser.
     *
     * Khronos Texture Container (.ktx) files are used to support this.  This format has the
     * advantage of being specifically designed for OpenGL.  Header elements directly correspond
     * to API arguments needed to compressed textures.  This puts the burden on the container
     * generator to house the arcane code for determining these for current & future formats.
     *
     * for description see https://www.khronos.org/opengles/sdk/tools/KTX/
     * for file layout see https://www.khronos.org/opengles/sdk/tools/KTX/file_format_spec/
     *
     * Note: The result of this call is not taken into account when a texture is base64.
     *
     * @param formatsAvailable defines the list of those format families you have created
     * on your server.  Syntax: '-' + format family + '.ktx'.  (Case and order do not matter.)
     *
     * Current families are astc, dxt, pvrtc, etc2, & etc1.
     * @returns The extension selected.
     */
    public setTextureFormatToUse(formatsAvailable: Array<string>): Nullable<string> {
        for (var i = 0, len1 = this.texturesSupported.length; i < len1; i++) {
            for (var j = 0, len2 = formatsAvailable.length; j < len2; j++) {
                if (this._texturesSupported[i] === formatsAvailable[j].toLowerCase()) {
                    return this._textureFormatInUse = this._texturesSupported[i];
                }
            }
        }
        // actively set format to nothing, to allow this to be called more than once
        // and possibly fail the 2nd time
        this._textureFormatInUse = null;
        return null;
    }

    private _getSamplingParameters(samplingMode: number, generateMipMaps: boolean): { min: number; mag: number } {
        var gl = this._gl;
        var magFilter = gl.NEAREST;
        var minFilter = gl.NEAREST;

        switch (samplingMode) {
            case Engine.TEXTURE_BILINEAR_SAMPLINGMODE:
                magFilter = gl.LINEAR;
                if (generateMipMaps) {
                    minFilter = gl.LINEAR_MIPMAP_NEAREST;
                } else {
                    minFilter = gl.LINEAR;
                }
                break;
            case Engine.TEXTURE_TRILINEAR_SAMPLINGMODE:
                magFilter = gl.LINEAR;
                if (generateMipMaps) {
                    minFilter = gl.LINEAR_MIPMAP_LINEAR;
                } else {
                    minFilter = gl.LINEAR;
                }
                break;
            case Engine.TEXTURE_NEAREST_SAMPLINGMODE:
                magFilter = gl.NEAREST;
                if (generateMipMaps) {
                    minFilter = gl.NEAREST_MIPMAP_LINEAR;
                } else {
                    minFilter = gl.NEAREST;
                }
                break;
            case Engine.TEXTURE_NEAREST_NEAREST_MIPNEAREST:
                magFilter = gl.NEAREST;
                if (generateMipMaps) {
                    minFilter = gl.NEAREST_MIPMAP_NEAREST;
                } else {
                    minFilter = gl.NEAREST;
                }
                break;
            case Engine.TEXTURE_NEAREST_LINEAR_MIPNEAREST:
                magFilter = gl.NEAREST;
                if (generateMipMaps) {
                    minFilter = gl.LINEAR_MIPMAP_NEAREST;
                } else {
                    minFilter = gl.LINEAR;
                }
                break;
            case Engine.TEXTURE_NEAREST_LINEAR_MIPLINEAR:
                magFilter = gl.NEAREST;
                if (generateMipMaps) {
                    minFilter = gl.LINEAR_MIPMAP_LINEAR;
                } else {
                    minFilter = gl.LINEAR;
                }
                break;
            case Engine.TEXTURE_NEAREST_LINEAR:
                magFilter = gl.NEAREST;
                minFilter = gl.LINEAR;
                break;
            case Engine.TEXTURE_NEAREST_NEAREST:
                magFilter = gl.NEAREST;
                minFilter = gl.NEAREST;
                break;
            case Engine.TEXTURE_LINEAR_NEAREST_MIPNEAREST:
                magFilter = gl.LINEAR;
                if (generateMipMaps) {
                    minFilter = gl.NEAREST_MIPMAP_NEAREST;
                } else {
                    minFilter = gl.NEAREST;
                }
                break;
            case Engine.TEXTURE_LINEAR_NEAREST_MIPLINEAR:
                magFilter = gl.LINEAR;
                if (generateMipMaps) {
                    minFilter = gl.NEAREST_MIPMAP_LINEAR;
                } else {
                    minFilter = gl.NEAREST;
                }
                break;
            case Engine.TEXTURE_LINEAR_LINEAR:
                magFilter = gl.LINEAR;
                minFilter = gl.LINEAR;
                break;
            case Engine.TEXTURE_LINEAR_NEAREST:
                magFilter = gl.LINEAR;
                minFilter = gl.NEAREST;
                break;
        }

        return {
            min: minFilter,
            mag: magFilter
        };
    }

    private _partialLoadImg(url: string, index: number, loadedImages: HTMLImageElement[], scene: Nullable<Scene>,
        onfinish: (images: HTMLImageElement[]) => void, onErrorCallBack: Nullable<(message?: string, exception?: any) => void> = null) {

        var img: HTMLImageElement;

        var onload = () => {
            loadedImages[index] = img;
            (<any>loadedImages)._internalCount++;

            if (scene) {
                scene._removePendingData(img);
            }

            if ((<any>loadedImages)._internalCount === 6) {
                onfinish(loadedImages);
            }
        };

        var onerror = (message?: string, exception?: any) => {
            if (scene) {
                scene._removePendingData(img);
            }

            if (onErrorCallBack) {
                onErrorCallBack(message, exception);
            }
        };

        img = Tools.LoadImage(url, onload, onerror, scene ? scene.offlineProvider : null);
        if (scene) {
            scene._addPendingData(img);
        }
    }

    private _cascadeLoadImgs(scene: Nullable<Scene>,
        onfinish: (images: HTMLImageElement[]) => void, files: string[], onError: Nullable<(message?: string, exception?: any) => void> = null) {

        var loadedImages: HTMLImageElement[] = [];
        (<any>loadedImages)._internalCount = 0;

        for (let index = 0; index < 6; index++) {
            this._partialLoadImg(files[index], index, loadedImages, scene, onfinish, onError);
        }
    }

    /** @hidden */
    public _createTexture(): WebGLTexture {
        let texture = this._gl.createTexture();

        if (!texture) {
            throw new Error("Unable to create texture");
        }

        return texture;
    }

    /**
     * Usually called from Texture.ts.
     * Passed information to create a WebGLTexture
     * @param urlArg defines a value which contains one of the following:
     * * A conventional http URL, e.g. 'http://...' or 'file://...'
     * * A base64 string of in-line texture data, e.g. 'data:image/jpg;base64,/...'
     * * An indicator that data being passed using the buffer parameter, e.g. 'data:mytexture.jpg'
     * @param noMipmap defines a boolean indicating that no mipmaps shall be generated.  Ignored for compressed textures.  They must be in the file
     * @param invertY when true, image is flipped when loaded.  You probably want true. Certain compressed textures may invert this if their default is inverted (eg. ktx)
     * @param scene needed for loading to the correct scene
     * @param samplingMode mode with should be used sample / access the texture (Default: Texture.TRILINEAR_SAMPLINGMODE)
     * @param onLoad optional callback to be called upon successful completion
     * @param onError optional callback to be called upon failure
     * @param buffer a source of a file previously fetched as either a base64 string, an ArrayBuffer (compressed or image format), HTMLImageElement (image format), or a Blob
     * @param fallback an internal argument in case the function must be called again, due to etc1 not having alpha capabilities
     * @param format internal format.  Default: RGB when extension is '.jpg' else RGBA.  Ignored for compressed textures
     * @param forcedExtension defines the extension to use to pick the right loader
     * @param excludeLoaders array of texture loaders that should be excluded when picking a loader for the texture (default: empty array)
     * @returns a InternalTexture for assignment back into BABYLON.Texture
     */
    public createTexture(urlArg: Nullable<string>, noMipmap: boolean, invertY: boolean, scene: Nullable<Scene>, samplingMode: number = Engine.TEXTURE_TRILINEAR_SAMPLINGMODE,
        onLoad: Nullable<() => void> = null, onError: Nullable<(message: string, exception: any) => void> = null,
        buffer: Nullable<string | ArrayBuffer | HTMLImageElement | Blob> = null, fallback: Nullable<InternalTexture> = null, format: Nullable<number> = null,
        forcedExtension: Nullable<string> = null, excludeLoaders: Array<IInternalTextureLoader> = []): InternalTexture {
        var url = String(urlArg); // assign a new string, so that the original is still available in case of fallback
        var fromData = url.substr(0, 5) === "data:";
        var fromBlob = url.substr(0, 5) === "blob:";
        var isBase64 = fromData && url.indexOf(";base64,") !== -1;

        let texture = fallback ? fallback : new InternalTexture(this, InternalTexture.DATASOURCE_URL);

        // establish the file extension, if possible
        var lastDot = url.lastIndexOf('.');
        var extension = forcedExtension ? forcedExtension : (lastDot > -1 ? url.substring(lastDot).toLowerCase() : "");

        let loader: Nullable<IInternalTextureLoader> = null;
        for (let availableLoader of Engine._TextureLoaders) {
            if (excludeLoaders.indexOf(availableLoader) === -1 && availableLoader.canLoad(extension, this._textureFormatInUse, fallback, isBase64, buffer ? true : false)) {
                loader = availableLoader;
                break;
            }
        }

        if (loader) {
            url = loader.transformUrl(url, this._textureFormatInUse);
        }

        if (scene) {
            scene._addPendingData(texture);
        }
        texture.url = url;
        texture.generateMipMaps = !noMipmap;
        texture.samplingMode = samplingMode;
        texture.invertY = invertY;

        if (!this._doNotHandleContextLost) {
            // Keep a link to the buffer only if we plan to handle context lost
            texture._buffer = buffer;
        }

        let onLoadObserver: Nullable<Observer<InternalTexture>> = null;
        if (onLoad && !fallback) {
            onLoadObserver = texture.onLoadedObservable.add(onLoad);
        }

        if (!fallback) { this._internalTexturesCache.push(texture); }

        let onInternalError = (message?: string, exception?: any) => {
            if (scene) {
                scene._removePendingData(texture);
            }

            let customFallback = false;
            if (loader) {
                const fallbackUrl = loader.getFallbackTextureUrl(url, this._textureFormatInUse);
                if (fallbackUrl) {
                    // Add Back
                    customFallback = true;
                    excludeLoaders.push(loader);
                    Tools.Warn((loader.constructor as any).name + " failed when trying to load " + texture.url + ", falling back to the next supported loader");
                    this.createTexture(urlArg, noMipmap, texture.invertY, scene, samplingMode, null, null, buffer, texture, undefined, undefined, excludeLoaders);
                }
            }

            if (!customFallback) {
                if (onLoadObserver) {
                    texture.onLoadedObservable.remove(onLoadObserver);
                }
                if (Tools.UseFallbackTexture) {
                    this.createTexture(Tools.fallbackTexture, noMipmap, texture.invertY, scene, samplingMode, null, null, buffer, texture);
                }
            }

            if (onError) {
                onError(message || "Unknown error", exception);
            }
        };

        // processing for non-image formats
        if (loader) {
            var callback = (data: string | ArrayBuffer) => {
                loader!.loadData(data as ArrayBuffer, texture, (width: number, height: number, loadMipmap: boolean, isCompressed: boolean, done: () => void, loadFailed) => {
                    if (loadFailed) {
                        onInternalError("TextureLoader failed to load data");
                    } else {
                        this._prepareWebGLTexture(texture, scene, width, height, texture.invertY, !loadMipmap, isCompressed, () => {
                            done();
                            return false;
                        }, samplingMode);
                    }
                });
            };

            if (!buffer) {
                this._loadFile(url, callback, undefined, scene ? scene.offlineProvider : undefined, true, (request?: WebRequest, exception?: any) => {
                    onInternalError("Unable to load " + (request ? request.responseURL : url, exception));
                });
            } else {
                callback(buffer as ArrayBuffer);
            }
        } else {
            var onload = (img: HTMLImageElement) => {
                if (fromBlob && !this._doNotHandleContextLost) {
                    // We need to store the image if we need to rebuild the texture
                    // in case of a webgl context lost
                    texture._buffer = img;
                }

                this._prepareWebGLTexture(texture, scene, img.width, img.height, texture.invertY, noMipmap, false, (potWidth, potHeight, continuationCallback) => {
                    let gl = this._gl;
                    var isPot = (img.width === potWidth && img.height === potHeight);
                    let internalFormat = format ? this._getInternalFormat(format) : ((extension === ".jpg") ? gl.RGB : gl.RGBA);

                    if (isPot) {
                        gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, internalFormat, gl.UNSIGNED_BYTE, img);
                        return false;
                    }

                    let maxTextureSize = this._caps.maxTextureSize;

                    if (img.width > maxTextureSize || img.height > maxTextureSize || Engine._RescalePostProcessFactory === null) {
                        this._prepareWorkingCanvas();
                        if (!this._workingCanvas || !this._workingContext) {
                            return false;
                        }

                        this._workingCanvas.width = potWidth;
                        this._workingCanvas.height = potHeight;

                        this._workingContext.drawImage(img, 0, 0, img.width, img.height, 0, 0, potWidth, potHeight);
                        gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, internalFormat, gl.UNSIGNED_BYTE, this._workingCanvas);

                        texture.width = potWidth;
                        texture.height = potHeight;

                        return false;
                    } else {
                        // Using shaders when possible to rescale because canvas.drawImage is lossy
                        let source = new InternalTexture(this, InternalTexture.DATASOURCE_TEMP);
                        this._bindTextureDirectly(gl.TEXTURE_2D, source, true);
                        gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, internalFormat, gl.UNSIGNED_BYTE, img);

                        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
                        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
                        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
                        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);

                        this._rescaleTexture(source, texture, scene, internalFormat, () => {
                            this._releaseTexture(source);
                            this._bindTextureDirectly(gl.TEXTURE_2D, texture, true);

                            continuationCallback();
                        });
                    }

                    return true;
                }, samplingMode);
            };

            if (!fromData || isBase64) {
                if (buffer instanceof HTMLImageElement) {
                    onload(buffer);
                } else {
                    Tools.LoadImage(url, onload, onInternalError, scene ? scene.offlineProvider : null);
                }
            }
            else if (typeof buffer === "string" || buffer instanceof ArrayBuffer || buffer instanceof Blob) {
                Tools.LoadImage(buffer, onload, onInternalError, scene ? scene.offlineProvider : null);
            }
            else {
                onload(<HTMLImageElement>buffer);
            }
        }

        return texture;
    }

    private _rescaleTexture(source: InternalTexture, destination: InternalTexture, scene: Nullable<Scene>, internalFormat: number, onComplete: () => void): void {
        let rtt = this.createRenderTargetTexture({
            width: destination.width,
            height: destination.height,
        }, {
                generateMipMaps: false,
                type: Engine.TEXTURETYPE_UNSIGNED_INT,
                samplingMode: Engine.TEXTURE_BILINEAR_SAMPLINGMODE,
                generateDepthBuffer: false,
                generateStencilBuffer: false
            }
        );

        if (!this._rescalePostProcess && Engine._RescalePostProcessFactory) {
            this._rescalePostProcess = Engine._RescalePostProcessFactory(this);
        }

        this._rescalePostProcess.getEffect().executeWhenCompiled(() => {
            this._rescalePostProcess.onApply = function(effect) {
                effect._bindTexture("textureSampler", source);
            };

            let hostingScene = scene;

            if (!hostingScene) {
                hostingScene = this.scenes[this.scenes.length - 1];
            }
            hostingScene.postProcessManager.directRender([this._rescalePostProcess], rtt, true);

            this._bindTextureDirectly(this._gl.TEXTURE_2D, destination, true);
            this._gl.copyTexImage2D(this._gl.TEXTURE_2D, 0, internalFormat, 0, 0, destination.width, destination.height, 0);

            this.unBindFramebuffer(rtt);
            this._releaseTexture(rtt);

            if (onComplete) {
                onComplete();
            }
        });
    }

    /**
     * Update a raw texture
     * @param texture defines the texture to update
     * @param data defines the data to store in the texture
     * @param format defines the format of the data
     * @param invertY defines if data must be stored with Y axis inverted
     * @param compression defines the compression used (null by default)
     * @param type defines the type fo the data (Engine.TEXTURETYPE_UNSIGNED_INT by default)
     */
    public updateRawTexture(texture: Nullable<InternalTexture>, data: Nullable<ArrayBufferView>, format: number, invertY: boolean, compression: Nullable<string> = null, type = Engine.TEXTURETYPE_UNSIGNED_INT): void {
        if (!texture) {
            return;
        }
        // babylon's internalSizedFomat but gl's texImage2D internalFormat
        var internalSizedFomat = this._getRGBABufferInternalSizedFormat(type, format);
        // babylon's internalFormat but gl's texImage2D format
        var internalFormat = this._getInternalFormat(format);
        var textureType = this._getWebGLTextureType(type);
        this._bindTextureDirectly(this._gl.TEXTURE_2D, texture, true);
        this._unpackFlipY(invertY === undefined ? true : (invertY ? true : false));

        if (!this._doNotHandleContextLost) {
            texture._bufferView = data;
            texture.format = format;
            texture.type = type;
            texture.invertY = invertY;
            texture._compression = compression;
        }

        if (texture.width % 4 !== 0) {
            this._gl.pixelStorei(this._gl.UNPACK_ALIGNMENT, 1);
        }

        if (compression && data) {
            this._gl.compressedTexImage2D(this._gl.TEXTURE_2D, 0, (<any>this.getCaps().s3tc)[compression], texture.width, texture.height, 0, <DataView>data);
        } else {
            this._gl.texImage2D(this._gl.TEXTURE_2D, 0, internalSizedFomat, texture.width, texture.height, 0, internalFormat, textureType, data);
        }

        if (texture.generateMipMaps) {
            this._gl.generateMipmap(this._gl.TEXTURE_2D);
        }
        this._bindTextureDirectly(this._gl.TEXTURE_2D, null);
        //  this.resetTextureCache();
        texture.isReady = true;
    }

    /**
     * Creates a raw texture
     * @param data defines the data to store in the texture
     * @param width defines the width of the texture
     * @param height defines the height of the texture
     * @param format defines the format of the data
     * @param generateMipMaps defines if the engine should generate the mip levels
     * @param invertY defines if data must be stored with Y axis inverted
     * @param samplingMode defines the required sampling mode (Texture.NEAREST_SAMPLINGMODE by default)
     * @param compression defines the compression used (null by default)
     * @param type defines the type fo the data (Engine.TEXTURETYPE_UNSIGNED_INT by default)
     * @returns the raw texture inside an InternalTexture
     */
    public createRawTexture(data: Nullable<ArrayBufferView>, width: number, height: number, format: number, generateMipMaps: boolean, invertY: boolean, samplingMode: number, compression: Nullable<string> = null, type: number = Engine.TEXTURETYPE_UNSIGNED_INT): InternalTexture {
        var texture = new InternalTexture(this, InternalTexture.DATASOURCE_RAW);
        texture.baseWidth = width;
        texture.baseHeight = height;
        texture.width = width;
        texture.height = height;
        texture.format = format;
        texture.generateMipMaps = generateMipMaps;
        texture.samplingMode = samplingMode;
        texture.invertY = invertY;
        texture._compression = compression;
        texture.type = type;

        if (!this._doNotHandleContextLost) {
            texture._bufferView = data;
        }

        this.updateRawTexture(texture, data, format, invertY, compression, type);
        this._bindTextureDirectly(this._gl.TEXTURE_2D, texture, true);

        // Filters
        var filters = this._getSamplingParameters(samplingMode, generateMipMaps);

        this._gl.texParameteri(this._gl.TEXTURE_2D, this._gl.TEXTURE_MAG_FILTER, filters.mag);
        this._gl.texParameteri(this._gl.TEXTURE_2D, this._gl.TEXTURE_MIN_FILTER, filters.min);

        if (generateMipMaps) {
            this._gl.generateMipmap(this._gl.TEXTURE_2D);
        }

        this._bindTextureDirectly(this._gl.TEXTURE_2D, null);

        this._internalTexturesCache.push(texture);

        return texture;
    }

    private _unpackFlipYCached: Nullable<boolean> = null;

    /**
     * In case you are sharing the context with other applications, it might
     * be interested to not cache the unpack flip y state to ensure a consistent
     * value would be set.
     */
    public enableUnpackFlipYCached = true;

    /** @hidden */
    public _unpackFlipY(value: boolean): void {
        if (this._unpackFlipYCached !== value) {
            this._gl.pixelStorei(this._gl.UNPACK_FLIP_Y_WEBGL, value ? 1 : 0);

            if (this.enableUnpackFlipYCached) {
                this._unpackFlipYCached = value;
            }
        }
    }

    /** @hidden */
    public _getUnpackAlignement(): number {
        return this._gl.getParameter(this._gl.UNPACK_ALIGNMENT);
    }

    /**
     * Creates a dynamic texture
     * @param width defines the width of the texture
     * @param height defines the height of the texture
     * @param generateMipMaps defines if the engine should generate the mip levels
     * @param samplingMode defines the required sampling mode (Texture.NEAREST_SAMPLINGMODE by default)
     * @returns the dynamic texture inside an InternalTexture
     */
    public createDynamicTexture(width: number, height: number, generateMipMaps: boolean, samplingMode: number): InternalTexture {
        var texture = new InternalTexture(this, InternalTexture.DATASOURCE_DYNAMIC);
        texture.baseWidth = width;
        texture.baseHeight = height;

        if (generateMipMaps) {
            width = this.needPOTTextures ? Tools.GetExponentOfTwo(width, this._caps.maxTextureSize) : width;
            height = this.needPOTTextures ? Tools.GetExponentOfTwo(height, this._caps.maxTextureSize) : height;
        }

        //  this.resetTextureCache();
        texture.width = width;
        texture.height = height;
        texture.isReady = false;
        texture.generateMipMaps = generateMipMaps;
        texture.samplingMode = samplingMode;

        this.updateTextureSamplingMode(samplingMode, texture);

        this._internalTexturesCache.push(texture);

        return texture;
    }

    /**
     * Update the sampling mode of a given texture
     * @param samplingMode defines the required sampling mode
     * @param texture defines the texture to update
     */
    public updateTextureSamplingMode(samplingMode: number, texture: InternalTexture): void {
        var filters = this._getSamplingParameters(samplingMode, texture.generateMipMaps);

        if (texture.isCube) {
            this._setTextureParameterInteger(this._gl.TEXTURE_CUBE_MAP, this._gl.TEXTURE_MAG_FILTER, filters.mag, texture);
            this._setTextureParameterInteger(this._gl.TEXTURE_CUBE_MAP, this._gl.TEXTURE_MIN_FILTER, filters.min);
            this._bindTextureDirectly(this._gl.TEXTURE_CUBE_MAP, null);
        } else if (texture.is3D) {
            this._setTextureParameterInteger(this._gl.TEXTURE_3D, this._gl.TEXTURE_MAG_FILTER, filters.mag, texture);
            this._setTextureParameterInteger(this._gl.TEXTURE_3D, this._gl.TEXTURE_MIN_FILTER, filters.min);
            this._bindTextureDirectly(this._gl.TEXTURE_3D, null);
        } else {
            this._setTextureParameterInteger(this._gl.TEXTURE_2D, this._gl.TEXTURE_MAG_FILTER, filters.mag, texture);
            this._setTextureParameterInteger(this._gl.TEXTURE_2D, this._gl.TEXTURE_MIN_FILTER, filters.min);
            this._bindTextureDirectly(this._gl.TEXTURE_2D, null);
        }

        texture.samplingMode = samplingMode;
    }

    /**
     * Update the content of a dynamic texture
     * @param texture defines the texture to update
     * @param canvas defines the canvas containing the source
     * @param invertY defines if data must be stored with Y axis inverted
     * @param premulAlpha defines if alpha is stored as premultiplied
     * @param format defines the format of the data
     * @param forceBindTexture if the texture should be forced to be bound eg. after a graphics context loss (Default: false)
     */
    public updateDynamicTexture(texture: Nullable<InternalTexture>, canvas: HTMLCanvasElement, invertY: boolean, premulAlpha: boolean = false, format?: number, forceBindTexture: boolean = false): void {
        if (!texture) {
            return;
        }

        this._bindTextureDirectly(this._gl.TEXTURE_2D, texture, true, forceBindTexture);
        this._unpackFlipY(invertY);
        if (premulAlpha) {
            this._gl.pixelStorei(this._gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, 1);
        }
        let internalFormat = format ? this._getInternalFormat(format) : this._gl.RGBA;
        this._gl.texImage2D(this._gl.TEXTURE_2D, 0, internalFormat, internalFormat, this._gl.UNSIGNED_BYTE, canvas);
        if (texture.generateMipMaps) {
            this._gl.generateMipmap(this._gl.TEXTURE_2D);
        }
        this._bindTextureDirectly(this._gl.TEXTURE_2D, null);
        if (premulAlpha) {
            this._gl.pixelStorei(this._gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, 0);
        }
        texture.isReady = true;
    }

    /**
     * Update a video texture
     * @param texture defines the texture to update
     * @param video defines the video element to use
     * @param invertY defines if data must be stored with Y axis inverted
     */
    public updateVideoTexture(texture: Nullable<InternalTexture>, video: HTMLVideoElement, invertY: boolean): void {
        if (!texture || texture._isDisabled) {
            return;
        }

        var wasPreviouslyBound = this._bindTextureDirectly(this._gl.TEXTURE_2D, texture, true);
        this._unpackFlipY(!invertY); // Video are upside down by default

        try {
            // Testing video texture support
            if (this._videoTextureSupported === undefined) {
                this._gl.texImage2D(this._gl.TEXTURE_2D, 0, this._gl.RGBA, this._gl.RGBA, this._gl.UNSIGNED_BYTE, video);

                if (this._gl.getError() !== 0) {
                    this._videoTextureSupported = false;
                } else {
                    this._videoTextureSupported = true;
                }
            }

            // Copy video through the current working canvas if video texture is not supported
            if (!this._videoTextureSupported) {
                if (!texture._workingCanvas) {
                    texture._workingCanvas = document.createElement("canvas");
                    let context = texture._workingCanvas.getContext("2d");

                    if (!context) {
                        throw new Error("Unable to get 2d context");
                    }

                    texture._workingContext = context;
                    texture._workingCanvas.width = texture.width;
                    texture._workingCanvas.height = texture.height;
                }

                texture._workingContext.drawImage(video, 0, 0, video.videoWidth, video.videoHeight, 0, 0, texture.width, texture.height);

                this._gl.texImage2D(this._gl.TEXTURE_2D, 0, this._gl.RGBA, this._gl.RGBA, this._gl.UNSIGNED_BYTE, texture._workingCanvas);
            } else {
                this._gl.texImage2D(this._gl.TEXTURE_2D, 0, this._gl.RGBA, this._gl.RGBA, this._gl.UNSIGNED_BYTE, video);
            }

            if (texture.generateMipMaps) {
                this._gl.generateMipmap(this._gl.TEXTURE_2D);
            }

            if (!wasPreviouslyBound) {
                this._bindTextureDirectly(this._gl.TEXTURE_2D, null);
            }
            //    this.resetTextureCache();
            texture.isReady = true;

        } catch (ex) {
            // Something unexpected
            // Let's disable the texture
            texture._isDisabled = true;
        }
    }

    /**
     * Updates a depth texture Comparison Mode and Function.
     * If the comparison Function is equal to 0, the mode will be set to none.
     * Otherwise, this only works in webgl 2 and requires a shadow sampler in the shader.
     * @param texture The texture to set the comparison function for
     * @param comparisonFunction The comparison function to set, 0 if no comparison required
     */
    public updateTextureComparisonFunction(texture: InternalTexture, comparisonFunction: number): void {
        if (this.webGLVersion === 1) {
            Logger.Error("WebGL 1 does not support texture comparison.");
            return;
        }

        var gl = this._gl;

        if (texture.isCube) {
            this._bindTextureDirectly(this._gl.TEXTURE_CUBE_MAP, texture, true);

            if (comparisonFunction === 0) {
                gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_COMPARE_FUNC, Engine.LEQUAL);
                gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_COMPARE_MODE, gl.NONE);
            }
            else {
                gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_COMPARE_FUNC, comparisonFunction);
                gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_COMPARE_MODE, gl.COMPARE_REF_TO_TEXTURE);
            }

            this._bindTextureDirectly(this._gl.TEXTURE_CUBE_MAP, null);
        } else {
            this._bindTextureDirectly(this._gl.TEXTURE_2D, texture, true);

            if (comparisonFunction === 0) {
                gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_COMPARE_FUNC, Engine.LEQUAL);
                gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_COMPARE_MODE, gl.NONE);
            }
            else {
                gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_COMPARE_FUNC, comparisonFunction);
                gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_COMPARE_MODE, gl.COMPARE_REF_TO_TEXTURE);
            }

            this._bindTextureDirectly(this._gl.TEXTURE_2D, null);
        }

        texture._comparisonFunction = comparisonFunction;
    }

    private _setupDepthStencilTexture(internalTexture: InternalTexture, size: number | { width: number, height: number }, generateStencil: boolean, bilinearFiltering: boolean, comparisonFunction: number): void {
        var width = (<{ width: number, height: number }>size).width || <number>size;
        var height = (<{ width: number, height: number }>size).height || <number>size;
        internalTexture.baseWidth = width;
        internalTexture.baseHeight = height;
        internalTexture.width = width;
        internalTexture.height = height;
        internalTexture.isReady = true;
        internalTexture.samples = 1;
        internalTexture.generateMipMaps = false;
        internalTexture._generateDepthBuffer = true;
        internalTexture._generateStencilBuffer = generateStencil;
        internalTexture.samplingMode = bilinearFiltering ? Engine.TEXTURE_BILINEAR_SAMPLINGMODE : Engine.TEXTURE_NEAREST_SAMPLINGMODE;
        internalTexture.type = Engine.TEXTURETYPE_UNSIGNED_INT;
        internalTexture._comparisonFunction = comparisonFunction;

        var gl = this._gl;
        var target = internalTexture.isCube ? gl.TEXTURE_CUBE_MAP : gl.TEXTURE_2D;
        var samplingParameters = this._getSamplingParameters(internalTexture.samplingMode, false);
        gl.texParameteri(target, gl.TEXTURE_MAG_FILTER, samplingParameters.mag);
        gl.texParameteri(target, gl.TEXTURE_MIN_FILTER, samplingParameters.min);
        gl.texParameteri(target, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
        gl.texParameteri(target, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);

        if (comparisonFunction === 0) {
            gl.texParameteri(target, gl.TEXTURE_COMPARE_FUNC, Engine.LEQUAL);
            gl.texParameteri(target, gl.TEXTURE_COMPARE_MODE, gl.NONE);
        }
        else {
            gl.texParameteri(target, gl.TEXTURE_COMPARE_FUNC, comparisonFunction);
            gl.texParameteri(target, gl.TEXTURE_COMPARE_MODE, gl.COMPARE_REF_TO_TEXTURE);
        }
    }

    /**
     * Creates a depth stencil texture.
     * This is only available in WebGL 2 or with the depth texture extension available.
     * @param size The size of face edge in the texture.
     * @param options The options defining the texture.
     * @returns The texture
     */
    public createDepthStencilTexture(size: number | { width: number, height: number }, options: DepthTextureCreationOptions): InternalTexture {
        if (options.isCube) {
            let width = (<{ width: number, height: number }>size).width || <number>size;
            return this._createDepthStencilCubeTexture(width, options);
        }
        else {
            return this._createDepthStencilTexture(size, options);
        }
    }

    /**
     * Creates a depth stencil texture.
     * This is only available in WebGL 2 or with the depth texture extension available.
     * @param size The size of face edge in the texture.
     * @param options The options defining the texture.
     * @returns The texture
     */
    private _createDepthStencilTexture(size: number | { width: number, height: number }, options: DepthTextureCreationOptions): InternalTexture {
        var internalTexture = new InternalTexture(this, InternalTexture.DATASOURCE_DEPTHTEXTURE);

        if (!this._caps.depthTextureExtension) {
            Logger.Error("Depth texture is not supported by your browser or hardware.");
            return internalTexture;
        }

        var internalOptions = {
            bilinearFiltering: false,
            comparisonFunction: 0,
            generateStencil: false,
            ...options
        };

        var gl = this._gl;
        this._bindTextureDirectly(gl.TEXTURE_2D, internalTexture, true);

        this._setupDepthStencilTexture(internalTexture, size, internalOptions.generateStencil, internalOptions.bilinearFiltering, internalOptions.comparisonFunction);

        if (this.webGLVersion > 1) {
            if (internalOptions.generateStencil) {
                gl.texImage2D(gl.TEXTURE_2D, 0, gl.DEPTH24_STENCIL8, internalTexture.width, internalTexture.height, 0, gl.DEPTH_STENCIL, gl.UNSIGNED_INT_24_8, null);
            }
            else {
                gl.texImage2D(gl.TEXTURE_2D, 0, gl.DEPTH_COMPONENT24, internalTexture.width, internalTexture.height, 0, gl.DEPTH_COMPONENT, gl.UNSIGNED_INT, null);
            }
        }
        else {
            if (internalOptions.generateStencil) {
                gl.texImage2D(gl.TEXTURE_2D, 0, gl.DEPTH_STENCIL, internalTexture.width, internalTexture.height, 0, gl.DEPTH_STENCIL, gl.UNSIGNED_INT_24_8, null);
            }
            else {
                gl.texImage2D(gl.TEXTURE_2D, 0, gl.DEPTH_COMPONENT, internalTexture.width, internalTexture.height, 0, gl.DEPTH_COMPONENT, gl.UNSIGNED_INT, null);
            }
        }

        this._bindTextureDirectly(gl.TEXTURE_2D, null);

        return internalTexture;
    }

    /**
     * Creates a depth stencil cube texture.
     * This is only available in WebGL 2.
     * @param size The size of face edge in the cube texture.
     * @param options The options defining the cube texture.
     * @returns The cube texture
     */
    private _createDepthStencilCubeTexture(size: number, options: DepthTextureCreationOptions): InternalTexture {
        var internalTexture = new InternalTexture(this, InternalTexture.DATASOURCE_UNKNOWN);
        internalTexture.isCube = true;

        if (this.webGLVersion === 1) {
            Logger.Error("Depth cube texture is not supported by WebGL 1.");
            return internalTexture;
        }

        var internalOptions = {
            bilinearFiltering: false,
            comparisonFunction: 0,
            generateStencil: false,
            ...options
        };

        var gl = this._gl;
        this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, internalTexture, true);

        this._setupDepthStencilTexture(internalTexture, size, internalOptions.generateStencil, internalOptions.bilinearFiltering, internalOptions.comparisonFunction);

        // Create the depth/stencil buffer
        for (var face = 0; face < 6; face++) {
            if (internalOptions.generateStencil) {
                gl.texImage2D(gl.TEXTURE_CUBE_MAP_POSITIVE_X + face, 0, gl.DEPTH24_STENCIL8, size, size, 0, gl.DEPTH_STENCIL, gl.UNSIGNED_INT_24_8, null);
            }
            else {
                gl.texImage2D(gl.TEXTURE_CUBE_MAP_POSITIVE_X + face, 0, gl.DEPTH_COMPONENT24, size, size, 0, gl.DEPTH_COMPONENT, gl.UNSIGNED_INT, null);
            }
        }

        this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, null);

        return internalTexture;
    }

    /**
     * Sets the frame buffer Depth / Stencil attachement of the render target to the defined depth stencil texture.
     * @param renderTarget The render target to set the frame buffer for
     */
    public setFrameBufferDepthStencilTexture(renderTarget: RenderTargetTexture): void {
        // Create the framebuffer
        var internalTexture = renderTarget.getInternalTexture();
        if (!internalTexture || !internalTexture._framebuffer || !renderTarget.depthStencilTexture) {
            return;
        }

        var gl = this._gl;
        var depthStencilTexture = renderTarget.depthStencilTexture;

        this.bindUnboundFramebuffer(internalTexture._framebuffer);
        if (depthStencilTexture.isCube) {
            if (depthStencilTexture._generateStencilBuffer) {
                gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.TEXTURE_CUBE_MAP_POSITIVE_X, depthStencilTexture._webGLTexture, 0);
            }
            else {
                gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.TEXTURE_CUBE_MAP_POSITIVE_X, depthStencilTexture._webGLTexture, 0);
            }
        }
        else {
            if (depthStencilTexture._generateStencilBuffer) {
                gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.TEXTURE_2D, depthStencilTexture._webGLTexture, 0);
            }
            else {
                gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.TEXTURE_2D, depthStencilTexture._webGLTexture, 0);
            }
        }
        this.bindUnboundFramebuffer(null);
    }

    /**
     * Creates a new render target texture
     * @param size defines the size of the texture
     * @param options defines the options used to create the texture
     * @returns a new render target texture stored in an InternalTexture
     */
    public createRenderTargetTexture(size: number | { width: number, height: number }, options: boolean | RenderTargetCreationOptions): InternalTexture {
        let fullOptions = new RenderTargetCreationOptions();

        if (options !== undefined && typeof options === "object") {
            fullOptions.generateMipMaps = options.generateMipMaps;
            fullOptions.generateDepthBuffer = options.generateDepthBuffer === undefined ? true : options.generateDepthBuffer;
            fullOptions.generateStencilBuffer = fullOptions.generateDepthBuffer && options.generateStencilBuffer;
            fullOptions.type = options.type === undefined ? Engine.TEXTURETYPE_UNSIGNED_INT : options.type;
            fullOptions.samplingMode = options.samplingMode === undefined ? Engine.TEXTURE_TRILINEAR_SAMPLINGMODE : options.samplingMode;
            fullOptions.format = options.format === undefined ? Engine.TEXTUREFORMAT_RGBA : options.format;
        } else {
            fullOptions.generateMipMaps = <boolean>options;
            fullOptions.generateDepthBuffer = true;
            fullOptions.generateStencilBuffer = false;
            fullOptions.type = Engine.TEXTURETYPE_UNSIGNED_INT;
            fullOptions.samplingMode = Engine.TEXTURE_TRILINEAR_SAMPLINGMODE;
            fullOptions.format = Engine.TEXTUREFORMAT_RGBA;
        }

        if (fullOptions.type === Engine.TEXTURETYPE_FLOAT && !this._caps.textureFloatLinearFiltering) {
            // if floating point linear (gl.FLOAT) then force to NEAREST_SAMPLINGMODE
            fullOptions.samplingMode = Engine.TEXTURE_NEAREST_SAMPLINGMODE;
        }
        else if (fullOptions.type === Engine.TEXTURETYPE_HALF_FLOAT && !this._caps.textureHalfFloatLinearFiltering) {
            // if floating point linear (HALF_FLOAT) then force to NEAREST_SAMPLINGMODE
            fullOptions.samplingMode = Engine.TEXTURE_NEAREST_SAMPLINGMODE;
        }
        var gl = this._gl;

        var texture = new InternalTexture(this, InternalTexture.DATASOURCE_RENDERTARGET);
        this._bindTextureDirectly(gl.TEXTURE_2D, texture, true);

        var width = (<{ width: number, height: number }>size).width || <number>size;
        var height = (<{ width: number, height: number }>size).height || <number>size;

        var filters = this._getSamplingParameters(fullOptions.samplingMode, fullOptions.generateMipMaps ? true : false);

        if (fullOptions.type === Engine.TEXTURETYPE_FLOAT && !this._caps.textureFloat) {
            fullOptions.type = Engine.TEXTURETYPE_UNSIGNED_INT;
            Logger.Warn("Float textures are not supported. Render target forced to TEXTURETYPE_UNSIGNED_BYTE type");
        }

        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, filters.mag);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, filters.min);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);

        gl.texImage2D(gl.TEXTURE_2D, 0, this._getRGBABufferInternalSizedFormat(fullOptions.type, fullOptions.format), width, height, 0, this._getInternalFormat(fullOptions.format), this._getWebGLTextureType(fullOptions.type), null);

        // Create the framebuffer
        var currentFrameBuffer = this._currentFramebuffer;
        var framebuffer = gl.createFramebuffer();
        this.bindUnboundFramebuffer(framebuffer);
        gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture._webGLTexture, 0);

        texture._depthStencilBuffer = this._setupFramebufferDepthAttachments(fullOptions.generateStencilBuffer ? true : false, fullOptions.generateDepthBuffer, width, height);

        if (fullOptions.generateMipMaps) {
            this._gl.generateMipmap(this._gl.TEXTURE_2D);
        }

        // Unbind
        this._bindTextureDirectly(gl.TEXTURE_2D, null);
        gl.bindRenderbuffer(gl.RENDERBUFFER, null);
        this.bindUnboundFramebuffer(currentFrameBuffer);

        texture._framebuffer = framebuffer;
        texture.baseWidth = width;
        texture.baseHeight = height;
        texture.width = width;
        texture.height = height;
        texture.isReady = true;
        texture.samples = 1;
        texture.generateMipMaps = fullOptions.generateMipMaps ? true : false;
        texture.samplingMode = fullOptions.samplingMode;
        texture.type = fullOptions.type;
        texture.format = fullOptions.format;
        texture._generateDepthBuffer = fullOptions.generateDepthBuffer;
        texture._generateStencilBuffer = fullOptions.generateStencilBuffer ? true : false;

        // this.resetTextureCache();

        this._internalTexturesCache.push(texture);

        return texture;
    }

    /**
     * Create a multi render target texture
     * @see http://doc.babylonjs.com/features/webgl2#multiple-render-target
     * @param size defines the size of the texture
     * @param options defines the creation options
     * @returns the cube texture as an InternalTexture
     */
    public createMultipleRenderTarget(size: any, options: IMultiRenderTargetOptions): InternalTexture[] {
        var generateMipMaps = false;
        var generateDepthBuffer = true;
        var generateStencilBuffer = false;
        var generateDepthTexture = false;
        var textureCount = 1;

        var defaultType = Engine.TEXTURETYPE_UNSIGNED_INT;
        var defaultSamplingMode = Engine.TEXTURE_TRILINEAR_SAMPLINGMODE;

        var types = new Array<number>();
        var samplingModes = new Array<number>();

        if (options !== undefined) {
            generateMipMaps = options.generateMipMaps === undefined ? false : options.generateMipMaps;
            generateDepthBuffer = options.generateDepthBuffer === undefined ? true : options.generateDepthBuffer;
            generateStencilBuffer = options.generateStencilBuffer === undefined ? false : options.generateStencilBuffer;
            generateDepthTexture = options.generateDepthTexture === undefined ? false : options.generateDepthTexture;
            textureCount = options.textureCount || 1;

            if (options.types) {
                types = options.types;
            }
            if (options.samplingModes) {
                samplingModes = options.samplingModes;
            }

        }
        var gl = this._gl;
        // Create the framebuffer
        var framebuffer = gl.createFramebuffer();
        this.bindUnboundFramebuffer(framebuffer);

        var width = size.width || size;
        var height = size.height || size;

        var textures = [];
        var attachments = [];

        var depthStencilBuffer = this._setupFramebufferDepthAttachments(generateStencilBuffer, generateDepthBuffer, width, height);

        for (var i = 0; i < textureCount; i++) {
            var samplingMode = samplingModes[i] || defaultSamplingMode;
            var type = types[i] || defaultType;

            if (type === Engine.TEXTURETYPE_FLOAT && !this._caps.textureFloatLinearFiltering) {
                // if floating point linear (gl.FLOAT) then force to NEAREST_SAMPLINGMODE
                samplingMode = Engine.TEXTURE_NEAREST_SAMPLINGMODE;
            }
            else if (type === Engine.TEXTURETYPE_HALF_FLOAT && !this._caps.textureHalfFloatLinearFiltering) {
                // if floating point linear (HALF_FLOAT) then force to NEAREST_SAMPLINGMODE
                samplingMode = Engine.TEXTURE_NEAREST_SAMPLINGMODE;
            }

            var filters = this._getSamplingParameters(samplingMode, generateMipMaps);
            if (type === Engine.TEXTURETYPE_FLOAT && !this._caps.textureFloat) {
                type = Engine.TEXTURETYPE_UNSIGNED_INT;
                Logger.Warn("Float textures are not supported. Render target forced to TEXTURETYPE_UNSIGNED_BYTE type");
            }

            var texture = new InternalTexture(this, InternalTexture.DATASOURCE_MULTIRENDERTARGET);
            var attachment = (<any>gl)[this.webGLVersion > 1 ? "COLOR_ATTACHMENT" + i : "COLOR_ATTACHMENT" + i + "_WEBGL"];

            textures.push(texture);
            attachments.push(attachment);

            gl.activeTexture((<any>gl)["TEXTURE" + i]);
            gl.bindTexture(gl.TEXTURE_2D, texture._webGLTexture);

            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, filters.mag);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, filters.min);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);

            gl.texImage2D(gl.TEXTURE_2D, 0, this._getRGBABufferInternalSizedFormat(type), width, height, 0, gl.RGBA, this._getWebGLTextureType(type), null);

            gl.framebufferTexture2D(gl.DRAW_FRAMEBUFFER, attachment, gl.TEXTURE_2D, texture._webGLTexture, 0);

            if (generateMipMaps) {
                this._gl.generateMipmap(this._gl.TEXTURE_2D);
            }

            // Unbind
            this._bindTextureDirectly(gl.TEXTURE_2D, null);

            texture._framebuffer = framebuffer;
            texture._depthStencilBuffer = depthStencilBuffer;
            texture.baseWidth = width;
            texture.baseHeight = height;
            texture.width = width;
            texture.height = height;
            texture.isReady = true;
            texture.samples = 1;
            texture.generateMipMaps = generateMipMaps;
            texture.samplingMode = samplingMode;
            texture.type = type;
            texture._generateDepthBuffer = generateDepthBuffer;
            texture._generateStencilBuffer = generateStencilBuffer;
            texture._attachments = attachments;

            this._internalTexturesCache.push(texture);
        }

        if (generateDepthTexture && this._caps.depthTextureExtension) {
            // Depth texture
            var depthTexture = new InternalTexture(this, InternalTexture.DATASOURCE_MULTIRENDERTARGET);

            gl.activeTexture(gl.TEXTURE0);
            gl.bindTexture(gl.TEXTURE_2D, depthTexture._webGLTexture);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
            gl.texImage2D(
                gl.TEXTURE_2D,
                0,
                this.webGLVersion < 2 ? gl.DEPTH_COMPONENT : gl.DEPTH_COMPONENT16,
                width,
                height,
                0,
                gl.DEPTH_COMPONENT,
                gl.UNSIGNED_SHORT,
                null
            );

            gl.framebufferTexture2D(
                gl.FRAMEBUFFER,
                gl.DEPTH_ATTACHMENT,
                gl.TEXTURE_2D,
                depthTexture._webGLTexture,
                0
            );

            depthTexture._framebuffer = framebuffer;
            depthTexture.baseWidth = width;
            depthTexture.baseHeight = height;
            depthTexture.width = width;
            depthTexture.height = height;
            depthTexture.isReady = true;
            depthTexture.samples = 1;
            depthTexture.generateMipMaps = generateMipMaps;
            depthTexture.samplingMode = gl.NEAREST;
            depthTexture._generateDepthBuffer = generateDepthBuffer;
            depthTexture._generateStencilBuffer = generateStencilBuffer;

            textures.push(depthTexture);
            this._internalTexturesCache.push(depthTexture);
        }

        gl.drawBuffers(attachments);
        gl.bindRenderbuffer(gl.RENDERBUFFER, null);
        this.bindUnboundFramebuffer(null);

        this.resetTextureCache();

        return textures;
    }

    private _setupFramebufferDepthAttachments(generateStencilBuffer: boolean, generateDepthBuffer: boolean, width: number, height: number, samples = 1): Nullable<WebGLRenderbuffer> {
        var depthStencilBuffer: Nullable<WebGLRenderbuffer> = null;
        var gl = this._gl;

        // Create the depth/stencil buffer
        if (generateStencilBuffer) {
            depthStencilBuffer = gl.createRenderbuffer();
            gl.bindRenderbuffer(gl.RENDERBUFFER, depthStencilBuffer);

            if (samples > 1) {
                gl.renderbufferStorageMultisample(gl.RENDERBUFFER, samples, gl.DEPTH24_STENCIL8, width, height);
            } else {
                gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_STENCIL, width, height);
            }

            gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, depthStencilBuffer);
        }
        else if (generateDepthBuffer) {
            depthStencilBuffer = gl.createRenderbuffer();
            gl.bindRenderbuffer(gl.RENDERBUFFER, depthStencilBuffer);

            if (samples > 1) {
                gl.renderbufferStorageMultisample(gl.RENDERBUFFER, samples, gl.DEPTH_COMPONENT16, width, height);
            } else {
                gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, width, height);
            }

            gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, depthStencilBuffer);
        }

        return depthStencilBuffer;
    }

    /**
     * Updates the sample count of a render target texture
     * @see http://doc.babylonjs.com/features/webgl2#multisample-render-targets
     * @param texture defines the texture to update
     * @param samples defines the sample count to set
     * @returns the effective sample count (could be 0 if multisample render targets are not supported)
     */
    public updateRenderTargetTextureSampleCount(texture: Nullable<InternalTexture>, samples: number): number {
        if (this.webGLVersion < 2 || !texture) {
            return 1;
        }

        if (texture.samples === samples) {
            return samples;
        }

        var gl = this._gl;

        samples = Math.min(samples, gl.getParameter(gl.MAX_SAMPLES));

        // Dispose previous render buffers
        if (texture._depthStencilBuffer) {
            gl.deleteRenderbuffer(texture._depthStencilBuffer);
            texture._depthStencilBuffer = null;
        }

        if (texture._MSAAFramebuffer) {
            gl.deleteFramebuffer(texture._MSAAFramebuffer);
            texture._MSAAFramebuffer = null;
        }

        if (texture._MSAARenderBuffer) {
            gl.deleteRenderbuffer(texture._MSAARenderBuffer);
            texture._MSAARenderBuffer = null;
        }

        if (samples > 1) {
            let framebuffer = gl.createFramebuffer();

            if (!framebuffer) {
                throw new Error("Unable to create multi sampled framebuffer");
            }

            texture._MSAAFramebuffer = framebuffer;
            this.bindUnboundFramebuffer(texture._MSAAFramebuffer);

            var colorRenderbuffer = gl.createRenderbuffer();

            if (!colorRenderbuffer) {
                throw new Error("Unable to create multi sampled framebuffer");
            }

            gl.bindRenderbuffer(gl.RENDERBUFFER, colorRenderbuffer);
            gl.renderbufferStorageMultisample(gl.RENDERBUFFER, samples, this._getRGBAMultiSampleBufferFormat(texture.type), texture.width, texture.height);

            gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, colorRenderbuffer);

            texture._MSAARenderBuffer = colorRenderbuffer;
        } else {
            this.bindUnboundFramebuffer(texture._framebuffer);
        }

        texture.samples = samples;
        texture._depthStencilBuffer = this._setupFramebufferDepthAttachments(texture._generateStencilBuffer, texture._generateDepthBuffer, texture.width, texture.height, samples);

        gl.bindRenderbuffer(gl.RENDERBUFFER, null);
        this.bindUnboundFramebuffer(null);

        return samples;
    }

    /**
     * Update the sample count for a given multiple render target texture
     * @see http://doc.babylonjs.com/features/webgl2#multisample-render-targets
     * @param textures defines the textures to update
     * @param samples defines the sample count to set
     * @returns the effective sample count (could be 0 if multisample render targets are not supported)
     */
    public updateMultipleRenderTargetTextureSampleCount(textures: Nullable<InternalTexture[]>, samples: number): number {
        if (this.webGLVersion < 2 || !textures || textures.length == 0) {
            return 1;
        }

        if (textures[0].samples === samples) {
            return samples;
        }

        var gl = this._gl;

        samples = Math.min(samples, gl.getParameter(gl.MAX_SAMPLES));

        // Dispose previous render buffers
        if (textures[0]._depthStencilBuffer) {
            gl.deleteRenderbuffer(textures[0]._depthStencilBuffer);
            textures[0]._depthStencilBuffer = null;
        }

        if (textures[0]._MSAAFramebuffer) {
            gl.deleteFramebuffer(textures[0]._MSAAFramebuffer);
            textures[0]._MSAAFramebuffer = null;
        }

        for (var i = 0; i < textures.length; i++) {
            if (textures[i]._MSAARenderBuffer) {
                gl.deleteRenderbuffer(textures[i]._MSAARenderBuffer);
                textures[i]._MSAARenderBuffer = null;
            }
        }

        if (samples > 1) {
            let framebuffer = gl.createFramebuffer();

            if (!framebuffer) {
                throw new Error("Unable to create multi sampled framebuffer");
            }

            this.bindUnboundFramebuffer(framebuffer);

            let depthStencilBuffer = this._setupFramebufferDepthAttachments(textures[0]._generateStencilBuffer, textures[0]._generateDepthBuffer, textures[0].width, textures[0].height, samples);

            var attachments = [];

            for (var i = 0; i < textures.length; i++) {
                var texture = textures[i];
                var attachment = (<any>gl)[this.webGLVersion > 1 ? "COLOR_ATTACHMENT" + i : "COLOR_ATTACHMENT" + i + "_WEBGL"];

                var colorRenderbuffer = gl.createRenderbuffer();

                if (!colorRenderbuffer) {
                    throw new Error("Unable to create multi sampled framebuffer");
                }

                gl.bindRenderbuffer(gl.RENDERBUFFER, colorRenderbuffer);
                gl.renderbufferStorageMultisample(gl.RENDERBUFFER, samples, this._getRGBAMultiSampleBufferFormat(texture.type), texture.width, texture.height);

                gl.framebufferRenderbuffer(gl.FRAMEBUFFER, attachment, gl.RENDERBUFFER, colorRenderbuffer);

                texture._MSAAFramebuffer = framebuffer;
                texture._MSAARenderBuffer = colorRenderbuffer;
                texture.samples = samples;
                texture._depthStencilBuffer = depthStencilBuffer;
                gl.bindRenderbuffer(gl.RENDERBUFFER, null);
                attachments.push(attachment);
            }
            gl.drawBuffers(attachments);
        } else {
            this.bindUnboundFramebuffer(textures[0]._framebuffer);
        }

        this.bindUnboundFramebuffer(null);

        return samples;
    }

    /** @hidden */
    public _uploadCompressedDataToTextureDirectly(texture: InternalTexture, internalFormat: number, width: number, height: number, data: ArrayBufferView, faceIndex: number = 0, lod: number = 0) {
        var gl = this._gl;

        var target = gl.TEXTURE_2D;
        if (texture.isCube) {
            target = gl.TEXTURE_CUBE_MAP_POSITIVE_X + faceIndex;
        }

        this._gl.compressedTexImage2D(target, lod, internalFormat, width, height, 0, <DataView>data);
    }

    /** @hidden */
    public _uploadDataToTextureDirectly(texture: InternalTexture, imageData: ArrayBufferView, faceIndex: number = 0, lod: number = 0): void {
        var gl = this._gl;

        var textureType = this._getWebGLTextureType(texture.type);
        var format = this._getInternalFormat(texture.format);
        var internalFormat = this._getRGBABufferInternalSizedFormat(texture.type, format);

        this._unpackFlipY(texture.invertY);

        var target = gl.TEXTURE_2D;
        if (texture.isCube) {
            target = gl.TEXTURE_CUBE_MAP_POSITIVE_X + faceIndex;
        }

        const lodMaxWidth = Math.round(Scalar.Log2(texture.width));
        const lodMaxHeight = Math.round(Scalar.Log2(texture.height));
        const width = Math.pow(2, Math.max(lodMaxWidth - lod, 0));
        const height = Math.pow(2, Math.max(lodMaxHeight - lod, 0));

        gl.texImage2D(target, lod, internalFormat, width, height, 0, format, textureType, imageData);
    }

    /** @hidden */
    public _uploadArrayBufferViewToTexture(texture: InternalTexture, imageData: ArrayBufferView, faceIndex: number = 0, lod: number = 0): void {
        var gl = this._gl;
        var bindTarget = texture.isCube ? gl.TEXTURE_CUBE_MAP : gl.TEXTURE_2D;

        this._bindTextureDirectly(bindTarget, texture, true);

        this._uploadDataToTextureDirectly(texture, imageData, faceIndex, lod);

        this._bindTextureDirectly(bindTarget, null, true);
    }

    /** @hidden */
    public _uploadImageToTexture(texture: InternalTexture, image: HTMLImageElement, faceIndex: number = 0, lod: number = 0) {
        var gl = this._gl;

        var textureType = this._getWebGLTextureType(texture.type);
        var format = this._getInternalFormat(texture.format);
        var internalFormat = this._getRGBABufferInternalSizedFormat(texture.type, format);

        var bindTarget = texture.isCube ? gl.TEXTURE_CUBE_MAP : gl.TEXTURE_2D;

        this._bindTextureDirectly(bindTarget, texture, true);
        this._unpackFlipY(texture.invertY);

        var target = gl.TEXTURE_2D;
        if (texture.isCube) {
            target = gl.TEXTURE_CUBE_MAP_POSITIVE_X + faceIndex;
        }

        gl.texImage2D(target, lod, internalFormat, format, textureType, image);
        this._bindTextureDirectly(bindTarget, null, true);
    }

    /**
     * Creates a new render target cube texture
     * @param size defines the size of the texture
     * @param options defines the options used to create the texture
     * @returns a new render target cube texture stored in an InternalTexture
     */
    public createRenderTargetCubeTexture(size: number, options?: Partial<RenderTargetCreationOptions>): InternalTexture {
        let fullOptions = {
            generateMipMaps: true,
            generateDepthBuffer: true,
            generateStencilBuffer: false,
            type: Engine.TEXTURETYPE_UNSIGNED_INT,
            samplingMode: Engine.TEXTURE_TRILINEAR_SAMPLINGMODE,
            format: Engine.TEXTUREFORMAT_RGBA,
            ...options
        };
        fullOptions.generateStencilBuffer = fullOptions.generateDepthBuffer && fullOptions.generateStencilBuffer;

        if (fullOptions.type === Engine.TEXTURETYPE_FLOAT && !this._caps.textureFloatLinearFiltering) {
            // if floating point linear (gl.FLOAT) then force to NEAREST_SAMPLINGMODE
            fullOptions.samplingMode = Engine.TEXTURE_NEAREST_SAMPLINGMODE;
        }
        else if (fullOptions.type === Engine.TEXTURETYPE_HALF_FLOAT && !this._caps.textureHalfFloatLinearFiltering) {
            // if floating point linear (HALF_FLOAT) then force to NEAREST_SAMPLINGMODE
            fullOptions.samplingMode = Engine.TEXTURE_NEAREST_SAMPLINGMODE;
        }
        var gl = this._gl;

        var texture = new InternalTexture(this, InternalTexture.DATASOURCE_RENDERTARGET);
        this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, texture, true);

        var filters = this._getSamplingParameters(fullOptions.samplingMode, fullOptions.generateMipMaps);

        if (fullOptions.type === Engine.TEXTURETYPE_FLOAT && !this._caps.textureFloat) {
            fullOptions.type = Engine.TEXTURETYPE_UNSIGNED_INT;
            Logger.Warn("Float textures are not supported. Cube render target forced to TEXTURETYPE_UNESIGNED_BYTE type");
        }

        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MAG_FILTER, filters.mag);
        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MIN_FILTER, filters.min);
        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);

        for (var face = 0; face < 6; face++) {
            gl.texImage2D((gl.TEXTURE_CUBE_MAP_POSITIVE_X + face), 0, this._getRGBABufferInternalSizedFormat(fullOptions.type, fullOptions.format), size, size, 0, this._getInternalFormat(fullOptions.format), this._getWebGLTextureType(fullOptions.type), null);
        }

        // Create the framebuffer
        var framebuffer = gl.createFramebuffer();
        this.bindUnboundFramebuffer(framebuffer);

        texture._depthStencilBuffer = this._setupFramebufferDepthAttachments(fullOptions.generateStencilBuffer, fullOptions.generateDepthBuffer, size, size);

        // MipMaps
        if (fullOptions.generateMipMaps) {
            gl.generateMipmap(gl.TEXTURE_CUBE_MAP);
        }

        // Unbind
        this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, null);
        gl.bindRenderbuffer(gl.RENDERBUFFER, null);
        this.bindUnboundFramebuffer(null);

        texture._framebuffer = framebuffer;
        texture.width = size;
        texture.height = size;
        texture.isReady = true;
        texture.isCube = true;
        texture.samples = 1;
        texture.generateMipMaps = fullOptions.generateMipMaps;
        texture.samplingMode = fullOptions.samplingMode;
        texture.type = fullOptions.type;
        texture.format = fullOptions.format;
        texture._generateDepthBuffer = fullOptions.generateDepthBuffer;
        texture._generateStencilBuffer = fullOptions.generateStencilBuffer;

        this._internalTexturesCache.push(texture);

        return texture;
    }

    /**
     * Creates a cube texture
     * @param rootUrl defines the url where the files to load is located
     * @param scene defines the current scene
     * @param files defines the list of files to load (1 per face)
     * @param noMipmap defines a boolean indicating that no mipmaps shall be generated (false by default)
     * @param onLoad defines an optional callback raised when the texture is loaded
     * @param onError defines an optional callback raised if there is an issue to load the texture
     * @param format defines the format of the data
     * @param forcedExtension defines the extension to use to pick the right loader
     * @param createPolynomials if a polynomial sphere should be created for the cube texture
     * @param lodScale defines the scale applied to environment texture. This manages the range of LOD level used for IBL according to the roughness
     * @param lodOffset defines the offset applied to environment texture. This manages first LOD level used for IBL according to the roughness
     * @param fallback defines texture to use while falling back when (compressed) texture file not found.
     * @param excludeLoaders array of texture loaders that should be excluded when picking a loader for the texture (defualt: empty array)
     * @returns the cube texture as an InternalTexture
     */
    public createCubeTexture(rootUrl: string, scene: Nullable<Scene>, files: Nullable<string[]>, noMipmap?: boolean, onLoad: Nullable<(data?: any) => void> = null, onError: Nullable<(message?: string, exception?: any) => void> = null, format?: number, forcedExtension: any = null, createPolynomials = false, lodScale: number = 0, lodOffset: number = 0, fallback: Nullable<InternalTexture> = null, excludeLoaders: Array<IInternalTextureLoader> = []): InternalTexture {
        var gl = this._gl;

        var texture = fallback ? fallback : new InternalTexture(this, InternalTexture.DATASOURCE_CUBE);
        texture.isCube = true;
        texture.url = rootUrl;
        texture.generateMipMaps = !noMipmap;
        texture._lodGenerationScale = lodScale;
        texture._lodGenerationOffset = lodOffset;

        if (!this._doNotHandleContextLost) {
            texture._extension = forcedExtension;
            texture._files = files;
        }

        var lastDot = rootUrl.lastIndexOf('.');
        var extension = forcedExtension ? forcedExtension : (lastDot > -1 ? rootUrl.substring(lastDot).toLowerCase() : "");

        let loader: Nullable<IInternalTextureLoader> = null;
        for (let availableLoader of Engine._TextureLoaders) {
            if (excludeLoaders.indexOf(availableLoader) === -1 && availableLoader.canLoad(extension, this._textureFormatInUse, fallback, false, false)) {
                loader = availableLoader;
                break;
            }
        }

        let onInternalError = (request?: WebRequest, exception?: any) => {
            if (loader) {
                const fallbackUrl = loader.getFallbackTextureUrl(texture.url, this._textureFormatInUse);
                Logger.Warn((loader.constructor as any).name + " failed when trying to load " + texture.url + ", falling back to the next supported loader");
                if (fallbackUrl) {
                    excludeLoaders.push(loader);
                    this.createCubeTexture(fallbackUrl, scene, files, noMipmap, onLoad, onError, format, extension, createPolynomials, lodScale, lodOffset, texture, excludeLoaders);
                    return;
                }
            }

            if (onError && request) {
                onError(request.status + " " + request.statusText, exception);
            }
        };

        if (loader) {
            rootUrl = loader.transformUrl(rootUrl, this._textureFormatInUse);

            const onloaddata = (data: any) => {
                this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, texture, true);
                loader!.loadCubeData(data, texture, createPolynomials, onLoad, onError);
            };
            if (files && files.length === 6) {
                if (loader.supportCascades) {
                    this._cascadeLoadFiles(scene, onloaddata, files, onError);
                }
                else if (onError) {
                    onError("Textures type does not support cascades.");
                }
            }
            else {
                this._loadFile(rootUrl, onloaddata, undefined, undefined, true, onInternalError);
            }
        }
        else {
            if (!files) {
                throw new Error("Cannot load cubemap because files were not defined");
            }

            this._cascadeLoadImgs(scene, (imgs) => {
                var width = this.needPOTTextures ? Tools.GetExponentOfTwo(imgs[0].width, this._caps.maxCubemapTextureSize) : imgs[0].width;
                var height = width;

                this._prepareWorkingCanvas();

                if (!this._workingCanvas || !this._workingContext) {
                    return;
                }
                this._workingCanvas.width = width;
                this._workingCanvas.height = height;

                var faces = [
                    gl.TEXTURE_CUBE_MAP_POSITIVE_X, gl.TEXTURE_CUBE_MAP_POSITIVE_Y, gl.TEXTURE_CUBE_MAP_POSITIVE_Z,
                    gl.TEXTURE_CUBE_MAP_NEGATIVE_X, gl.TEXTURE_CUBE_MAP_NEGATIVE_Y, gl.TEXTURE_CUBE_MAP_NEGATIVE_Z
                ];

                this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, texture, true);
                this._unpackFlipY(false);

                let internalFormat = format ? this._getInternalFormat(format) : this._gl.RGBA;
                for (var index = 0; index < faces.length; index++) {
                    if (imgs[index].width !== width || imgs[index].height !== height) {
                        this._workingContext.drawImage(imgs[index], 0, 0, imgs[index].width, imgs[index].height, 0, 0, width, height);
                        gl.texImage2D(faces[index], 0, internalFormat, internalFormat, gl.UNSIGNED_BYTE, this._workingCanvas);
                    } else {
                        gl.texImage2D(faces[index], 0, internalFormat, internalFormat, gl.UNSIGNED_BYTE, imgs[index]);
                    }
                }

                if (!noMipmap) {
                    gl.generateMipmap(gl.TEXTURE_CUBE_MAP);
                }

                this._setCubeMapTextureParams(!noMipmap);

                texture.width = width;
                texture.height = height;
                texture.isReady = true;
                if (format) {
                    texture.format = format;
                }

                texture.onLoadedObservable.notifyObservers(texture);
                texture.onLoadedObservable.clear();

                if (onLoad) {
                    onLoad();
                }
            }, files, onError);
        }

        this._internalTexturesCache.push(texture);

        return texture;
    }

    /**
     * @hidden
     */
    public _setCubeMapTextureParams(loadMipmap: boolean): void {
        var gl = this._gl;
        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MIN_FILTER, loadMipmap ? gl.LINEAR_MIPMAP_LINEAR : gl.LINEAR);
        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);

        this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, null);

        //  this.resetTextureCache();
    }

    /**
     * Update a raw cube texture
     * @param texture defines the texture to udpdate
     * @param data defines the data to store
     * @param format defines the data format
     * @param type defines the type fo the data (Engine.TEXTURETYPE_UNSIGNED_INT by default)
     * @param invertY defines if data must be stored with Y axis inverted
     * @param compression defines the compression used (null by default)
     * @param level defines which level of the texture to update
     */
    public updateRawCubeTexture(texture: InternalTexture, data: ArrayBufferView[], format: number, type: number, invertY: boolean, compression: Nullable<string> = null, level = 0): void {
        texture._bufferViewArray = data;
        texture.format = format;
        texture.type = type;
        texture.invertY = invertY;
        texture._compression = compression;

        var gl = this._gl;
        var textureType = this._getWebGLTextureType(type);
        var internalFormat = this._getInternalFormat(format);
        var internalSizedFomat = this._getRGBABufferInternalSizedFormat(type);

        var needConversion = false;
        if (internalFormat === gl.RGB) {
            internalFormat = gl.RGBA;
            needConversion = true;
        }

        this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, texture, true);
        this._unpackFlipY(invertY === undefined ? true : (invertY ? true : false));

        if (texture.width % 4 !== 0) {
            gl.pixelStorei(gl.UNPACK_ALIGNMENT, 1);
        }

        // Data are known to be in +X +Y +Z -X -Y -Z
        for (let faceIndex = 0; faceIndex < 6; faceIndex++) {
            let faceData = data[faceIndex];

            if (compression) {
                gl.compressedTexImage2D(gl.TEXTURE_CUBE_MAP_POSITIVE_X + faceIndex, level, (<any>(this.getCaps().s3tc))[compression], texture.width, texture.height, 0, <DataView>faceData);
            } else {
                if (needConversion) {
                    faceData = this._convertRGBtoRGBATextureData(faceData, texture.width, texture.height, type);
                }
                gl.texImage2D(gl.TEXTURE_CUBE_MAP_POSITIVE_X + faceIndex, level, internalSizedFomat, texture.width, texture.height, 0, internalFormat, textureType, faceData);
            }
        }

        var isPot = !this.needPOTTextures || (Tools.IsExponentOfTwo(texture.width) && Tools.IsExponentOfTwo(texture.height));
        if (isPot && texture.generateMipMaps && level === 0) {
            this._gl.generateMipmap(this._gl.TEXTURE_CUBE_MAP);
        }
        this._bindTextureDirectly(this._gl.TEXTURE_CUBE_MAP, null);

        // this.resetTextureCache();
        texture.isReady = true;
    }

    /**
     * Creates a new raw cube texture
     * @param data defines the array of data to use to create each face
     * @param size defines the size of the textures
     * @param format defines the format of the data
     * @param type defines the type of the data (like Engine.TEXTURETYPE_UNSIGNED_INT)
     * @param generateMipMaps  defines if the engine should generate the mip levels
     * @param invertY defines if data must be stored with Y axis inverted
     * @param samplingMode defines the required sampling mode (like Texture.NEAREST_SAMPLINGMODE)
     * @param compression defines the compression used (null by default)
     * @returns the cube texture as an InternalTexture
     */
    public createRawCubeTexture(data: Nullable<ArrayBufferView[]>, size: number, format: number, type: number,
        generateMipMaps: boolean, invertY: boolean, samplingMode: number,
        compression: Nullable<string> = null): InternalTexture {
        var gl = this._gl;
        var texture = new InternalTexture(this, InternalTexture.DATASOURCE_CUBERAW);
        texture.isCube = true;
        texture.format = format;
        texture.type = type;
        if (!this._doNotHandleContextLost) {
            texture._bufferViewArray = data;
        }

        var textureType = this._getWebGLTextureType(type);
        var internalFormat = this._getInternalFormat(format);

        if (internalFormat === gl.RGB) {
            internalFormat = gl.RGBA;
        }

        // Mipmap generation needs a sized internal format that is both color-renderable and texture-filterable
        if (textureType === gl.FLOAT && !this._caps.textureFloatLinearFiltering) {
            generateMipMaps = false;
            samplingMode = Engine.TEXTURE_NEAREST_SAMPLINGMODE;
            Logger.Warn("Float texture filtering is not supported. Mipmap generation and sampling mode are forced to false and TEXTURE_NEAREST_SAMPLINGMODE, respectively.");
        }
        else if (textureType === this._gl.HALF_FLOAT_OES && !this._caps.textureHalfFloatLinearFiltering) {
            generateMipMaps = false;
            samplingMode = Engine.TEXTURE_NEAREST_SAMPLINGMODE;
            Logger.Warn("Half float texture filtering is not supported. Mipmap generation and sampling mode are forced to false and TEXTURE_NEAREST_SAMPLINGMODE, respectively.");
        }
        else if (textureType === gl.FLOAT && !this._caps.textureFloatRender) {
            generateMipMaps = false;
            Logger.Warn("Render to float textures is not supported. Mipmap generation forced to false.");
        }
        else if (textureType === gl.HALF_FLOAT && !this._caps.colorBufferFloat) {
            generateMipMaps = false;
            Logger.Warn("Render to half float textures is not supported. Mipmap generation forced to false.");
        }

        var width = size;
        var height = width;

        texture.width = width;
        texture.height = height;

        // Double check on POT to generate Mips.
        var isPot = !this.needPOTTextures || (Tools.IsExponentOfTwo(texture.width) && Tools.IsExponentOfTwo(texture.height));
        if (!isPot) {
            generateMipMaps = false;
        }

        // Upload data if needed. The texture won't be ready until then.
        if (data) {
            this.updateRawCubeTexture(texture, data, format, type, invertY, compression);
        }

        this._bindTextureDirectly(this._gl.TEXTURE_CUBE_MAP, texture, true);

        // Filters
        if (data && generateMipMaps) {
            this._gl.generateMipmap(this._gl.TEXTURE_CUBE_MAP);
        }

        var filters = this._getSamplingParameters(samplingMode, generateMipMaps);
        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MAG_FILTER, filters.mag);
        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MIN_FILTER, filters.min);

        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
        gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
        this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, null);

        texture.generateMipMaps = generateMipMaps;

        return texture;
    }

    /**
     * Creates a new raw cube texture from a specified url
     * @param url defines the url where the data is located
     * @param scene defines the current scene
     * @param size defines the size of the textures
     * @param format defines the format of the data
     * @param type defines the type fo the data (like Engine.TEXTURETYPE_UNSIGNED_INT)
     * @param noMipmap defines if the engine should avoid generating the mip levels
     * @param callback defines a callback used to extract texture data from loaded data
     * @param mipmapGenerator defines to provide an optional tool to generate mip levels
     * @param onLoad defines a callback called when texture is loaded
     * @param onError defines a callback called if there is an error
     * @param samplingMode defines the required sampling mode (like Texture.NEAREST_SAMPLINGMODE)
     * @param invertY defines if data must be stored with Y axis inverted
     * @returns the cube texture as an InternalTexture
     */
    public createRawCubeTextureFromUrl(url: string, scene: Scene, size: number, format: number, type: number, noMipmap: boolean,
        callback: (ArrayBuffer: ArrayBuffer) => Nullable<ArrayBufferView[]>,
        mipmapGenerator: Nullable<((faces: ArrayBufferView[]) => ArrayBufferView[][])>,
        onLoad: Nullable<() => void> = null,
        onError: Nullable<(message?: string, exception?: any) => void> = null,
        samplingMode = Engine.TEXTURE_TRILINEAR_SAMPLINGMODE,
        invertY = false): InternalTexture {

        var gl = this._gl;
        var texture = this.createRawCubeTexture(null, size, format, type, !noMipmap, invertY, samplingMode);
        scene._addPendingData(texture);
        texture.url = url;
        this._internalTexturesCache.push(texture);

        var onerror = (request?: WebRequest, exception?: any) => {
            scene._removePendingData(texture);
            if (onError && request) {
                onError(request.status + " " + request.statusText, exception);
            }
        };

        var internalCallback = (data: any) => {
            var width = texture.width;
            var faceDataArrays = callback(data);

            if (!faceDataArrays) {
                return;
            }

            if (mipmapGenerator) {
                var textureType = this._getWebGLTextureType(type);
                var internalFormat = this._getInternalFormat(format);
                var internalSizedFomat = this._getRGBABufferInternalSizedFormat(type);

                var needConversion = false;
                if (internalFormat === gl.RGB) {
                    internalFormat = gl.RGBA;
                    needConversion = true;
                }

                this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, texture, true);
                this._unpackFlipY(false);

                var mipData = mipmapGenerator(faceDataArrays);
                for (var level = 0; level < mipData.length; level++) {
                    var mipSize = width >> level;

                    for (var faceIndex = 0; faceIndex < 6; faceIndex++) {
                        let mipFaceData = mipData[level][faceIndex];
                        if (needConversion) {
                            mipFaceData = this._convertRGBtoRGBATextureData(mipFaceData, mipSize, mipSize, type);
                        }
                        gl.texImage2D(faceIndex, level, internalSizedFomat, mipSize, mipSize, 0, internalFormat, textureType, mipFaceData);
                    }
                }

                this._bindTextureDirectly(gl.TEXTURE_CUBE_MAP, null);
            }
            else {
                this.updateRawCubeTexture(texture, faceDataArrays, format, type, invertY);
            }

            texture.isReady = true;
            // this.resetTextureCache();
            scene._removePendingData(texture);

            if (onLoad) {
                onLoad();
            }
        };

        this._loadFile(url, (data) => {
            internalCallback(data);
        }, undefined, scene.offlineProvider, true, onerror);

        return texture;
    }

    /**
     * Update a raw 3D texture
     * @param texture defines the texture to update
     * @param data defines the data to store
     * @param format defines the data format
     * @param invertY defines if data must be stored with Y axis inverted
     * @param compression defines the used compression (can be null)
     * @param textureType defines the texture Type (Engine.TEXTURETYPE_UNSIGNED_INT, Engine.TEXTURETYPE_FLOAT...)
     */
    public updateRawTexture3D(texture: InternalTexture, data: Nullable<ArrayBufferView>, format: number, invertY: boolean, compression: Nullable<string> = null, textureType = Engine.TEXTURETYPE_UNSIGNED_INT): void {
        var internalType = this._getWebGLTextureType(textureType);
        var internalFormat = this._getInternalFormat(format);
        var internalSizedFomat = this._getRGBABufferInternalSizedFormat(textureType, format);

        this._bindTextureDirectly(this._gl.TEXTURE_3D, texture, true);
        this._unpackFlipY(invertY === undefined ? true : (invertY ? true : false));

        if (!this._doNotHandleContextLost) {
            texture._bufferView = data;
            texture.format = format;
            texture.invertY = invertY;
            texture._compression = compression;
        }

        if (texture.width % 4 !== 0) {
            this._gl.pixelStorei(this._gl.UNPACK_ALIGNMENT, 1);
        }

        if (compression && data) {
            this._gl.compressedTexImage3D(this._gl.TEXTURE_3D, 0, (<any>this.getCaps().s3tc)[compression], texture.width, texture.height, texture.depth, 0, data);
        } else {
            this._gl.texImage3D(this._gl.TEXTURE_3D, 0, internalSizedFomat, texture.width, texture.height, texture.depth, 0, internalFormat, internalType, data);
        }

        if (texture.generateMipMaps) {
            this._gl.generateMipmap(this._gl.TEXTURE_3D);
        }
        this._bindTextureDirectly(this._gl.TEXTURE_3D, null);
        // this.resetTextureCache();
        texture.isReady = true;
    }

    /**
     * Creates a new raw 3D texture
     * @param data defines the data used to create the texture
     * @param width defines the width of the texture
     * @param height defines the height of the texture
     * @param depth defines the depth of the texture
     * @param format defines the format of the texture
     * @param generateMipMaps defines if the engine must generate mip levels
     * @param invertY defines if data must be stored with Y axis inverted
     * @param samplingMode defines the required sampling mode (like Texture.NEAREST_SAMPLINGMODE)
     * @param compression defines the compressed used (can be null)
     * @param textureType defines the compressed used (can be null)
     * @returns a new raw 3D texture (stored in an InternalTexture)
     */
    public createRawTexture3D(data: Nullable<ArrayBufferView>, width: number, height: number, depth: number, format: number, generateMipMaps: boolean, invertY: boolean, samplingMode: number, compression: Nullable<string> = null, textureType = Engine.TEXTURETYPE_UNSIGNED_INT): InternalTexture {
        var texture = new InternalTexture(this, InternalTexture.DATASOURCE_RAW3D);
        texture.baseWidth = width;
        texture.baseHeight = height;
        texture.baseDepth = depth;
        texture.width = width;
        texture.height = height;
        texture.depth = depth;
        texture.format = format;
        texture.type = textureType;
        texture.generateMipMaps = generateMipMaps;
        texture.samplingMode = samplingMode;
        texture.is3D = true;

        if (!this._doNotHandleContextLost) {
            texture._bufferView = data;
        }

        this.updateRawTexture3D(texture, data, format, invertY, compression, textureType);
        this._bindTextureDirectly(this._gl.TEXTURE_3D, texture, true);

        // Filters
        var filters = this._getSamplingParameters(samplingMode, generateMipMaps);

        this._gl.texParameteri(this._gl.TEXTURE_3D, this._gl.TEXTURE_MAG_FILTER, filters.mag);
        this._gl.texParameteri(this._gl.TEXTURE_3D, this._gl.TEXTURE_MIN_FILTER, filters.min);

        if (generateMipMaps) {
            this._gl.generateMipmap(this._gl.TEXTURE_3D);
        }

        this._bindTextureDirectly(this._gl.TEXTURE_3D, null);

        this._internalTexturesCache.push(texture);

        return texture;
    }

    private _prepareWebGLTextureContinuation(texture: InternalTexture, scene: Nullable<Scene>, noMipmap: boolean, isCompressed: boolean, samplingMode: number): void {
        var gl = this._gl;
        if (!gl) {
            return;
        }

        var filters = this._getSamplingParameters(samplingMode, !noMipmap);

        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, filters.mag);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, filters.min);

        if (!noMipmap && !isCompressed) {
            gl.generateMipmap(gl.TEXTURE_2D);
        }

        this._bindTextureDirectly(gl.TEXTURE_2D, null);

        // this.resetTextureCache();
        if (scene) {
            scene._removePendingData(texture);
        }

        texture.onLoadedObservable.notifyObservers(texture);
        texture.onLoadedObservable.clear();
    }

    private _prepareWebGLTexture(texture: InternalTexture, scene: Nullable<Scene>, width: number, height: number, invertY: boolean, noMipmap: boolean, isCompressed: boolean,
        processFunction: (width: number, height: number, continuationCallback: () => void) => boolean, samplingMode: number = Engine.TEXTURE_TRILINEAR_SAMPLINGMODE): void {
        var maxTextureSize = this.getCaps().maxTextureSize;
        var potWidth = Math.min(maxTextureSize, this.needPOTTextures ? Tools.GetExponentOfTwo(width, maxTextureSize) : width);
        var potHeight = Math.min(maxTextureSize, this.needPOTTextures ? Tools.GetExponentOfTwo(height, maxTextureSize) : height);

        var gl = this._gl;
        if (!gl) {
            return;
        }

        if (!texture._webGLTexture) {
            //  this.resetTextureCache();
            if (scene) {
                scene._removePendingData(texture);
            }

            return;
        }

        this._bindTextureDirectly(gl.TEXTURE_2D, texture, true);
        this._unpackFlipY(invertY === undefined ? true : (invertY ? true : false));

        texture.baseWidth = width;
        texture.baseHeight = height;
        texture.width = potWidth;
        texture.height = potHeight;
        texture.isReady = true;

        if (processFunction(potWidth, potHeight, () => {
            this._prepareWebGLTextureContinuation(texture, scene, noMipmap, isCompressed, samplingMode);
        })) {
            // Returning as texture needs extra async steps
            return;
        }

        this._prepareWebGLTextureContinuation(texture, scene, noMipmap, isCompressed, samplingMode);
    }

    private _convertRGBtoRGBATextureData(rgbData: any, width: number, height: number, textureType: number): ArrayBufferView {
        // Create new RGBA data container.
        var rgbaData: any;
        if (textureType === Engine.TEXTURETYPE_FLOAT) {
            rgbaData = new Float32Array(width * height * 4);
        }
        else {
            rgbaData = new Uint32Array(width * height * 4);
        }

        // Convert each pixel.
        for (let x = 0; x < width; x++) {
            for (let y = 0; y < height; y++) {
                let index = (y * width + x) * 3;
                let newIndex = (y * width + x) * 4;

                // Map Old Value to new value.
                rgbaData[newIndex + 0] = rgbData[index + 0];
                rgbaData[newIndex + 1] = rgbData[index + 1];
                rgbaData[newIndex + 2] = rgbData[index + 2];

                // Add fully opaque alpha channel.
                rgbaData[newIndex + 3] = 1;
            }
        }

        return rgbaData;
    }

    /** @hidden */
    public _releaseFramebufferObjects(texture: InternalTexture): void {
        var gl = this._gl;

        if (texture._framebuffer) {
            gl.deleteFramebuffer(texture._framebuffer);
            texture._framebuffer = null;
        }

        if (texture._depthStencilBuffer) {
            gl.deleteRenderbuffer(texture._depthStencilBuffer);
            texture._depthStencilBuffer = null;
        }

        if (texture._MSAAFramebuffer) {
            gl.deleteFramebuffer(texture._MSAAFramebuffer);
            texture._MSAAFramebuffer = null;
        }

        if (texture._MSAARenderBuffer) {
            gl.deleteRenderbuffer(texture._MSAARenderBuffer);
            texture._MSAARenderBuffer = null;
        }
    }

    /** @hidden */
    public _releaseTexture(texture: InternalTexture): void {
        var gl = this._gl;

        this._releaseFramebufferObjects(texture);

        gl.deleteTexture(texture._webGLTexture);

        // Unbind channels
        this.unbindAllTextures();

        var index = this._internalTexturesCache.indexOf(texture);
        if (index !== -1) {
            this._internalTexturesCache.splice(index, 1);
        }

        // Integrated fixed lod samplers.
        if (texture._lodTextureHigh) {
            texture._lodTextureHigh.dispose();
        }
        if (texture._lodTextureMid) {
            texture._lodTextureMid.dispose();
        }
        if (texture._lodTextureLow) {
            texture._lodTextureLow.dispose();
        }

        // Set output texture of post process to null if the texture has been released/disposed
        this.scenes.forEach((scene) => {
            scene.postProcesses.forEach((postProcess) => {
                if (postProcess._outputTexture == texture) {
                    postProcess._outputTexture = null;
                }
            });
            scene.cameras.forEach((camera) => {
                camera._postProcesses.forEach((postProcess) => {
                    if (postProcess) {
                        if (postProcess._outputTexture == texture) {
                            postProcess._outputTexture = null;
                        }
                    }
                });
            });
        });
    }

    private setProgram(program: WebGLProgram): void {
        if (this._currentProgram !== program) {
            this._gl.useProgram(program);
            this._currentProgram = program;
        }
    }

    private _boundUniforms: { [key: number]: WebGLUniformLocation } = {};

    /**
     * Binds an effect to the webGL context
     * @param effect defines the effect to bind
     */
    public bindSamplers(effect: Effect): void {
        this.setProgram(effect.getProgram());

        var samplers = effect.getSamplers();
        for (var index = 0; index < samplers.length; index++) {
            var uniform = effect.getUniform(samplers[index]);

            if (uniform) {
                this._boundUniforms[index] = uniform;
            }
        }
        this._currentEffect = null;
    }

    private _moveBoundTextureOnTop(internalTexture: InternalTexture): void {
        if (this.disableTextureBindingOptimization || this._lastBoundInternalTextureTracker.previous === internalTexture) {
            return;
        }

        // Remove
        this._linkTrackers(internalTexture.previous, internalTexture.next);

        // Bind last to it
        this._linkTrackers(this._lastBoundInternalTextureTracker.previous, internalTexture);

        // Bind to dummy
        this._linkTrackers(internalTexture, this._lastBoundInternalTextureTracker);
    }

    private _getCorrectTextureChannel(channel: number, internalTexture: Nullable<InternalTexture>): number {
        if (!internalTexture) {
            return -1;
        }

        internalTexture._initialSlot = channel;

        if (this.disableTextureBindingOptimization) { // We want texture sampler ID === texture channel
            if (channel !== internalTexture._designatedSlot) {
                this._textureCollisions.addCount(1, false);
            }
        } else {
            if (channel !== internalTexture._designatedSlot) {
                if (internalTexture._designatedSlot > -1) { // Texture is already assigned to a slot
                    return internalTexture._designatedSlot;
                } else {
                    // No slot for this texture, let's pick a new one (if we find a free slot)
                    if (this._nextFreeTextureSlots.length) {
                        return this._nextFreeTextureSlots[0];
                    }

                    // We need to recycle the oldest bound texture, sorry.
                    this._textureCollisions.addCount(1, false);
                    return this._removeDesignatedSlot(<InternalTexture>this._firstBoundInternalTextureTracker.next);
                }
            }
        }

        return channel;
    }

    private _linkTrackers(previous: Nullable<IInternalTextureTracker>, next: Nullable<IInternalTextureTracker>) {
        previous!.next = next;
        next!.previous = previous;
    }

    private _removeDesignatedSlot(internalTexture: InternalTexture): number {
        let currentSlot = internalTexture._designatedSlot;
        if (currentSlot === -1) {
            return -1;
        }

        internalTexture._designatedSlot = -1;

        if (this.disableTextureBindingOptimization) {
            return -1;
        }

        // Remove from bound list
        this._linkTrackers(internalTexture.previous, internalTexture.next);

        // Free the slot
        this._boundTexturesCache[currentSlot] = null;
        this._nextFreeTextureSlots.push(currentSlot);

        return currentSlot;
    }

    private _activateCurrentTexture() {
        if (this._currentTextureChannel !== this._activeChannel) {
            this._gl.activeTexture(this._gl.TEXTURE0 + this._activeChannel);
            this._currentTextureChannel = this._activeChannel;
        }
    }

    /** @hidden */
    public _bindTextureDirectly(target: number, texture: Nullable<InternalTexture>, forTextureDataUpdate = false, force = false): boolean {
        var wasPreviouslyBound = false;
        if (forTextureDataUpdate && texture && texture._designatedSlot > -1) {
            this._activeChannel = texture._designatedSlot;
        }

        let currentTextureBound = this._boundTexturesCache[this._activeChannel];
        let isTextureForRendering = texture && texture._initialSlot > -1;

        if (currentTextureBound !== texture || force) {
            if (currentTextureBound) {
                this._removeDesignatedSlot(currentTextureBound);
            }

            this._activateCurrentTexture();

            this._gl.bindTexture(target, texture ? texture._webGLTexture : null);
            this._boundTexturesCache[this._activeChannel] = texture;

            if (texture) {
                if (!this.disableTextureBindingOptimization) {
                    let slotIndex = this._nextFreeTextureSlots.indexOf(this._activeChannel);
                    if (slotIndex > -1) {
                        this._nextFreeTextureSlots.splice(slotIndex, 1);
                    }

                    this._linkTrackers(this._lastBoundInternalTextureTracker.previous, texture);
                    this._linkTrackers(texture, this._lastBoundInternalTextureTracker);
                }

                texture._designatedSlot = this._activeChannel;
            }
        } else if (forTextureDataUpdate) {
            wasPreviouslyBound = true;
            this._activateCurrentTexture();
        }

        if (isTextureForRendering && !forTextureDataUpdate) {
            this._bindSamplerUniformToChannel(texture!._initialSlot, this._activeChannel);
        }

        return wasPreviouslyBound;
    }

    /** @hidden */
    public _bindTexture(channel: number, texture: Nullable<InternalTexture>): void {
        if (channel < 0) {
            return;
        }

        if (texture) {
            channel = this._getCorrectTextureChannel(channel, texture);
        }

        this._activeChannel = channel;
        this._bindTextureDirectly(this._gl.TEXTURE_2D, texture);
    }

    /**
     * Sets a texture to the webGL context from a postprocess
     * @param channel defines the channel to use
     * @param postProcess defines the source postprocess
     */
    public setTextureFromPostProcess(channel: number, postProcess: Nullable<PostProcess>): void {
        this._bindTexture(channel, postProcess ? postProcess._textures.data[postProcess._currentRenderTextureInd] : null);
    }

    /**
     * Binds the output of the passed in post process to the texture channel specified
     * @param channel The channel the texture should be bound to
     * @param postProcess The post process which's output should be bound
     */
    public setTextureFromPostProcessOutput(channel: number, postProcess: Nullable<PostProcess>): void {
        this._bindTexture(channel, postProcess ? postProcess._outputTexture : null);
    }

    /**
     * Unbind all textures from the webGL context
     */
    public unbindAllTextures(): void {
        for (var channel = 0; channel < this._maxSimultaneousTextures; channel++) {
            this._activeChannel = channel;
            this._bindTextureDirectly(this._gl.TEXTURE_2D, null);
            this._bindTextureDirectly(this._gl.TEXTURE_CUBE_MAP, null);
            if (this.webGLVersion > 1) {
                this._bindTextureDirectly(this._gl.TEXTURE_3D, null);
            }
        }
    }

    /**
     * Sets a texture to the according uniform.
     * @param channel The texture channel
     * @param uniform The uniform to set
     * @param texture The texture to apply
     */
    public setTexture(channel: number, uniform: Nullable<WebGLUniformLocation>, texture: Nullable<BaseTexture>): void {
        if (channel < 0) {
            return;
        }

        if (uniform) {
            this._boundUniforms[channel] = uniform;
        }

        this._setTexture(channel, texture);
    }

    /**
     * Sets a depth stencil texture from a render target to the according uniform.
     * @param channel The texture channel
     * @param uniform The uniform to set
     * @param texture The render target texture containing the depth stencil texture to apply
     */
    public setDepthStencilTexture(channel: number, uniform: Nullable<WebGLUniformLocation>, texture: Nullable<RenderTargetTexture>): void {
        if (channel < 0) {
            return;
        }

        if (uniform) {
            this._boundUniforms[channel] = uniform;
        }

        if (!texture || !texture.depthStencilTexture) {
            this._setTexture(channel, null);
        }
        else {
            this._setTexture(channel, texture, false, true);
        }
    }

    private _bindSamplerUniformToChannel(sourceSlot: number, destination: number) {
        let uniform = this._boundUniforms[sourceSlot];
        if (uniform._currentState === destination) {
            return;
        }
        this._gl.uniform1i(uniform, destination);
        uniform._currentState = destination;
    }

    private _getTextureWrapMode(mode: number): number {
        switch (mode) {
            case Engine.TEXTURE_WRAP_ADDRESSMODE:
                return this._gl.REPEAT;
            case Engine.TEXTURE_CLAMP_ADDRESSMODE:
                return this._gl.CLAMP_TO_EDGE;
            case Engine.TEXTURE_MIRROR_ADDRESSMODE:
                return this._gl.MIRRORED_REPEAT;
        }
        return this._gl.REPEAT;
    }

    private _setTexture(channel: number, texture: Nullable<BaseTexture>, isPartOfTextureArray = false, depthStencilTexture = false): boolean {
        // Not ready?
        if (!texture) {
            if (this._boundTexturesCache[channel] != null) {
                this._activeChannel = channel;
                this._bindTextureDirectly(this._gl.TEXTURE_2D, null);
                this._bindTextureDirectly(this._gl.TEXTURE_CUBE_MAP, null);
                if (this.webGLVersion > 1) {
                    this._bindTextureDirectly(this._gl.TEXTURE_3D, null);
                }
            }
            return false;
        }

        // Video
        if ((<VideoTexture>texture).video) {
            this._activeChannel = channel;
            (<VideoTexture>texture).update();
        } else if (texture.delayLoadState === Engine.DELAYLOADSTATE_NOTLOADED) { // Delay loading
            texture.delayLoad();
            return false;
        }

        let internalTexture: InternalTexture;
        if (depthStencilTexture) {
            internalTexture = (<RenderTargetTexture>texture).depthStencilTexture!;
        }
        else if (texture.isReady()) {
            internalTexture = <InternalTexture>texture.getInternalTexture();
        }
        else if (texture.isCube) {
            internalTexture = this.emptyCubeTexture;
        }
        else if (texture.is3D) {
            internalTexture = this.emptyTexture3D;
        }
        else {
            internalTexture = this.emptyTexture;
        }

        if (!isPartOfTextureArray) {
            channel = this._getCorrectTextureChannel(channel, internalTexture);
        }

        let needToBind = true;
        if (this._boundTexturesCache[channel] === internalTexture) {
            this._moveBoundTextureOnTop(internalTexture);
            if (!isPartOfTextureArray) {
                this._bindSamplerUniformToChannel(internalTexture._initialSlot, channel);
            }

            needToBind = false;
        }

        this._activeChannel = channel;

        if (internalTexture && internalTexture.is3D) {
            if (needToBind) {
                this._bindTextureDirectly(this._gl.TEXTURE_3D, internalTexture, isPartOfTextureArray);
            }

            if (internalTexture && internalTexture._cachedWrapU !== texture.wrapU) {
                internalTexture._cachedWrapU = texture.wrapU;
                this._setTextureParameterInteger(this._gl.TEXTURE_3D, this._gl.TEXTURE_WRAP_S, this._getTextureWrapMode(texture.wrapU), internalTexture);
            }

            if (internalTexture && internalTexture._cachedWrapV !== texture.wrapV) {
                internalTexture._cachedWrapV = texture.wrapV;
                this._setTextureParameterInteger(this._gl.TEXTURE_3D, this._gl.TEXTURE_WRAP_T, this._getTextureWrapMode(texture.wrapV), internalTexture);
            }

            if (internalTexture && internalTexture._cachedWrapR !== texture.wrapR) {
                internalTexture._cachedWrapR = texture.wrapR;
                this._setTextureParameterInteger(this._gl.TEXTURE_3D, this._gl.TEXTURE_WRAP_R, this._getTextureWrapMode(texture.wrapR), internalTexture);
            }

            this._setAnisotropicLevel(this._gl.TEXTURE_3D, texture);
        }
        else if (internalTexture && internalTexture.isCube) {
            if (needToBind) {
                this._bindTextureDirectly(this._gl.TEXTURE_CUBE_MAP, internalTexture, isPartOfTextureArray);
            }

            if (internalTexture._cachedCoordinatesMode !== texture.coordinatesMode) {
                internalTexture._cachedCoordinatesMode = texture.coordinatesMode;
                // CUBIC_MODE and SKYBOX_MODE both require CLAMP_TO_EDGE.  All other modes use REPEAT.
                var textureWrapMode = (texture.coordinatesMode !== Engine.TEXTURE_CUBIC_MODE && texture.coordinatesMode !== Engine.TEXTURE_SKYBOX_MODE) ? this._gl.REPEAT : this._gl.CLAMP_TO_EDGE;
                this._setTextureParameterInteger(this._gl.TEXTURE_CUBE_MAP, this._gl.TEXTURE_WRAP_S, textureWrapMode, internalTexture);
                this._setTextureParameterInteger(this._gl.TEXTURE_CUBE_MAP, this._gl.TEXTURE_WRAP_T, textureWrapMode);
            }

            this._setAnisotropicLevel(this._gl.TEXTURE_CUBE_MAP, texture);
        } else {
            if (needToBind) {
                this._bindTextureDirectly(this._gl.TEXTURE_2D, internalTexture, isPartOfTextureArray);
            }

            if (internalTexture && internalTexture._cachedWrapU !== texture.wrapU) {
                internalTexture._cachedWrapU = texture.wrapU;
                this._setTextureParameterInteger(this._gl.TEXTURE_2D, this._gl.TEXTURE_WRAP_S, this._getTextureWrapMode(texture.wrapU), internalTexture);
            }

            if (internalTexture && internalTexture._cachedWrapV !== texture.wrapV) {
                internalTexture._cachedWrapV = texture.wrapV;
                this._setTextureParameterInteger(this._gl.TEXTURE_2D, this._gl.TEXTURE_WRAP_T, this._getTextureWrapMode(texture.wrapV), internalTexture);
            }

            this._setAnisotropicLevel(this._gl.TEXTURE_2D, texture);
        }

        return true;
    }

    /**
     * Sets an array of texture to the webGL context
     * @param channel defines the channel where the texture array must be set
     * @param uniform defines the associated uniform location
     * @param textures defines the array of textures to bind
     */
    public setTextureArray(channel: number, uniform: Nullable<WebGLUniformLocation>, textures: BaseTexture[]): void {
        if (channel < 0 || !uniform) {
            return;
        }

        if (!this._textureUnits || this._textureUnits.length !== textures.length) {
            this._textureUnits = new Int32Array(textures.length);
        }
        for (let i = 0; i < textures.length; i++) {
            this._textureUnits[i] = this._getCorrectTextureChannel(channel + i, textures[i].getInternalTexture());
        }
        this._gl.uniform1iv(uniform, this._textureUnits);

        for (var index = 0; index < textures.length; index++) {
            this._setTexture(this._textureUnits[index], textures[index], true);
        }
    }

    /** @hidden */
    public _setAnisotropicLevel(target: number, texture: BaseTexture) {
        var internalTexture = texture.getInternalTexture();

        if (!internalTexture) {
            return;
        }

        var anisotropicFilterExtension = this._caps.textureAnisotropicFilterExtension;
        var value = texture.anisotropicFilteringLevel;

        if (internalTexture.samplingMode !== Engine.TEXTURE_LINEAR_LINEAR_MIPNEAREST
            && internalTexture.samplingMode !== Engine.TEXTURE_LINEAR_LINEAR_MIPLINEAR
            && internalTexture.samplingMode !== Engine.TEXTURE_LINEAR_LINEAR) {
            value = 1; // Forcing the anisotropic to 1 because else webgl will force filters to linear
        }

        if (anisotropicFilterExtension && internalTexture._cachedAnisotropicFilteringLevel !== value) {
            this._setTextureParameterFloat(target, anisotropicFilterExtension.TEXTURE_MAX_ANISOTROPY_EXT, Math.min(value, this._caps.maxAnisotropy), internalTexture);
            internalTexture._cachedAnisotropicFilteringLevel = value;
        }
    }

    private _setTextureParameterFloat(target: number, parameter: number, value: number, texture: InternalTexture): void {
        this._bindTextureDirectly(target, texture, true, true);
        this._gl.texParameterf(target, parameter, value);
    }

    private _setTextureParameterInteger(target: number, parameter: number, value: number, texture?: InternalTexture) {
        if (texture) {
            this._bindTextureDirectly(target, texture, true, true);
        }
        this._gl.texParameteri(target, parameter, value);
    }

    /**
     * Reads pixels from the current frame buffer. Please note that this function can be slow
     * @param x defines the x coordinate of the rectangle where pixels must be read
     * @param y defines the y coordinate of the rectangle where pixels must be read
     * @param width defines the width of the rectangle where pixels must be read
     * @param height defines the height of the rectangle where pixels must be read
     * @returns a Uint8Array containing RGBA colors
     */
    public readPixels(x: number, y: number, width: number, height: number): Uint8Array {
        var data = new Uint8Array(height * width * 4);
        this._gl.readPixels(x, y, width, height, this._gl.RGBA, this._gl.UNSIGNED_BYTE, data);
        return data;
    }

    /**
     * Add an externaly attached data from its key.
     * This method call will fail and return false, if such key already exists.
     * If you don't care and just want to get the data no matter what, use the more convenient getOrAddExternalDataWithFactory() method.
     * @param key the unique key that identifies the data
     * @param data the data object to associate to the key for this Engine instance
     * @return true if no such key were already present and the data was added successfully, false otherwise
     */
    public addExternalData<T>(key: string, data: T): boolean {
        if (!this._externalData) {
            this._externalData = new StringDictionary<Object>();
        }
        return this._externalData.add(key, data);
    }

    /**
     * Get an externaly attached data from its key
     * @param key the unique key that identifies the data
     * @return the associated data, if present (can be null), or undefined if not present
     */
    public getExternalData<T>(key: string): T {
        if (!this._externalData) {
            this._externalData = new StringDictionary<Object>();
        }
        return <T>this._externalData.get(key);
    }

    /**
     * Get an externaly attached data from its key, create it using a factory if it's not already present
     * @param key the unique key that identifies the data
     * @param factory the factory that will be called to create the instance if and only if it doesn't exists
     * @return the associated data, can be null if the factory returned null.
     */
    public getOrAddExternalDataWithFactory<T>(key: string, factory: (k: string) => T): T {
        if (!this._externalData) {
            this._externalData = new StringDictionary<Object>();
        }
        return <T>this._externalData.getOrAddWithFactory(key, factory);
    }

    /**
     * Remove an externaly attached data from the Engine instance
     * @param key the unique key that identifies the data
     * @return true if the data was successfully removed, false if it doesn't exist
     */
    public removeExternalData(key: string): boolean {
        if (!this._externalData) {
            this._externalData = new StringDictionary<Object>();
        }

        return this._externalData.remove(key);
    }

    /**
     * Unbind all vertex attributes from the webGL context
     */
    public unbindAllAttributes() {
        if (this._mustWipeVertexAttributes) {
            this._mustWipeVertexAttributes = false;

            for (var i = 0; i < this._caps.maxVertexAttribs; i++) {
                this._gl.disableVertexAttribArray(i);
                this._vertexAttribArraysEnabled[i] = false;
                this._currentBufferPointers[i].active = false;
            }
            return;
        }

        for (var i = 0, ul = this._vertexAttribArraysEnabled.length; i < ul; i++) {
            if (i >= this._caps.maxVertexAttribs || !this._vertexAttribArraysEnabled[i]) {
                continue;
            }

            this._gl.disableVertexAttribArray(i);
            this._vertexAttribArraysEnabled[i] = false;
            this._currentBufferPointers[i].active = false;
        }
    }

    /**
     * Force the engine to release all cached effects. This means that next effect compilation will have to be done completely even if a similar effect was already compiled
     */
    public releaseEffects() {
        for (var name in this._compiledEffects) {
            this._deleteProgram(this._compiledEffects[name]._program);
        }

        this._compiledEffects = {};
    }

    /**
     * Dispose and release all associated resources
     */
    public dispose(): void {
        this.hideLoadingUI();

        this.stopRenderLoop();

        this.onNewSceneAddedObservable.clear();

        // Release postProcesses
        while (this.postProcesses.length) {
            this.postProcesses[0].dispose();
        }

        // Empty texture
        if (this._emptyTexture) {
            this._releaseTexture(this._emptyTexture);
            this._emptyTexture = null;
        }
        if (this._emptyCubeTexture) {
            this._releaseTexture(this._emptyCubeTexture);
            this._emptyCubeTexture = null;
        }

        // Rescale PP
        if (this._rescalePostProcess) {
            this._rescalePostProcess.dispose();
        }

        // Release scenes
        while (this.scenes.length) {
            this.scenes[0].dispose();
        }

        // Release audio engine
        if (Engine.Instances.length === 1 && Engine.audioEngine) {
            Engine.audioEngine.dispose();
        }

        // Release effects
        this.releaseEffects();

        // Unbind
        this.unbindAllAttributes();
        this._boundUniforms = [];

        if (this._dummyFramebuffer) {
            this._gl.deleteFramebuffer(this._dummyFramebuffer);
        }

        //WebVR
        this.disableVR();

        // Events
        if (DomManagement.IsWindowObjectExist()) {
            window.removeEventListener("blur", this._onBlur);
            window.removeEventListener("focus", this._onFocus);
            window.removeEventListener('vrdisplaypointerrestricted', this._onVRDisplayPointerRestricted);
            window.removeEventListener('vrdisplaypointerunrestricted', this._onVRDisplayPointerUnrestricted);
            if (this._renderingCanvas) {
                this._renderingCanvas.removeEventListener("focus", this._onCanvasFocus);
                this._renderingCanvas.removeEventListener("blur", this._onCanvasBlur);
                this._renderingCanvas.removeEventListener("pointerout", this._onCanvasPointerOut);

                if (!this._doNotHandleContextLost) {
                    this._renderingCanvas.removeEventListener("webglcontextlost", this._onContextLost);
                    this._renderingCanvas.removeEventListener("webglcontextrestored", this._onContextRestored);
                }
            }
            document.removeEventListener("fullscreenchange", this._onFullscreenChange);
            document.removeEventListener("mozfullscreenchange", this._onFullscreenChange);
            document.removeEventListener("webkitfullscreenchange", this._onFullscreenChange);
            document.removeEventListener("msfullscreenchange", this._onFullscreenChange);
            document.removeEventListener("pointerlockchange", this._onPointerLockChange);
            document.removeEventListener("mspointerlockchange", this._onPointerLockChange);
            document.removeEventListener("mozpointerlockchange", this._onPointerLockChange);
            document.removeEventListener("webkitpointerlockchange", this._onPointerLockChange);

            if (this._onVrDisplayConnect) {
                window.removeEventListener('vrdisplayconnect', this._onVrDisplayConnect);
                if (this._onVrDisplayDisconnect) {
                    window.removeEventListener('vrdisplaydisconnect', this._onVrDisplayDisconnect);
                }

                if (this._onVrDisplayPresentChange) {
                    window.removeEventListener('vrdisplaypresentchange', this._onVrDisplayPresentChange);
                }
                this._onVrDisplayConnect = null;
                this._onVrDisplayDisconnect = null;
            }
        }

        // Remove from Instances
        var index = Engine.Instances.indexOf(this);

        if (index >= 0) {
            Engine.Instances.splice(index, 1);
        }

        this._workingCanvas = null;
        this._workingContext = null;
        this._currentBufferPointers = [];
        this._renderingCanvas = null;
        this._currentProgram = null;
        this._bindedRenderFunction = null;

        this.onResizeObservable.clear();
        this.onCanvasBlurObservable.clear();
        this.onCanvasFocusObservable.clear();
        this.onCanvasPointerOutObservable.clear();
        this.onBeginFrameObservable.clear();
        this.onEndFrameObservable.clear();

        Effect.ResetCache();

        // Abort active requests
        for (let request of this._activeRequests) {
            request.abort();
        }
    }

    // Loading screen

    /**
     * Display the loading screen
     * @see http://doc.babylonjs.com/how_to/creating_a_custom_loading_screen
     */
    public displayLoadingUI(): void {
        if (!DomManagement.IsWindowObjectExist()) {
            return;
        }
        const loadingScreen = this.loadingScreen;
        if (loadingScreen) {
            loadingScreen.displayLoadingUI();
        }
    }

    /**
     * Hide the loading screen
     * @see http://doc.babylonjs.com/how_to/creating_a_custom_loading_screen
     */
    public hideLoadingUI(): void {
        if (!DomManagement.IsWindowObjectExist()) {
            return;
        }
        const loadingScreen = this.loadingScreen;
        if (loadingScreen) {
            loadingScreen.hideLoadingUI();
        }
    }

    /**
     * Gets the current loading screen object
     * @see http://doc.babylonjs.com/how_to/creating_a_custom_loading_screen
     */
    public get loadingScreen(): ILoadingScreen {
        if (!this._loadingScreen && this._renderingCanvas) {
            this._loadingScreen = Engine.DefaultLoadingScreenFactory(this._renderingCanvas);
        }
        return this._loadingScreen;
    }

    /**
     * Sets the current loading screen object
     * @see http://doc.babylonjs.com/how_to/creating_a_custom_loading_screen
     */
    public set loadingScreen(loadingScreen: ILoadingScreen) {
        this._loadingScreen = loadingScreen;
    }

    /**
     * Sets the current loading screen text
     * @see http://doc.babylonjs.com/how_to/creating_a_custom_loading_screen
     */
    public set loadingUIText(text: string) {
        this.loadingScreen.loadingUIText = text;
    }

    /**
     * Sets the current loading screen background color
     * @see http://doc.babylonjs.com/how_to/creating_a_custom_loading_screen
     */
    public set loadingUIBackgroundColor(color: string) {
        this.loadingScreen.loadingUIBackgroundColor = color;
    }

    /**
     * Attach a new callback raised when context lost event is fired
     * @param callback defines the callback to call
     */
    public attachContextLostEvent(callback: ((event: WebGLContextEvent) => void)): void {
        if (this._renderingCanvas) {
            this._renderingCanvas.addEventListener("webglcontextlost", <any>callback, false);
        }
    }

    /**
     * Attach a new callback raised when context restored event is fired
     * @param callback defines the callback to call
     */
    public attachContextRestoredEvent(callback: ((event: WebGLContextEvent) => void)): void {
        if (this._renderingCanvas) {
            this._renderingCanvas.addEventListener("webglcontextrestored", <any>callback, false);
        }
    }

    /**
     * Gets the source code of the vertex shader associated with a specific webGL program
     * @param program defines the program to use
     * @returns a string containing the source code of the vertex shader associated with the program
     */
    public getVertexShaderSource(program: WebGLProgram): Nullable<string> {
        var shaders = this._gl.getAttachedShaders(program);

        if (!shaders) {
            return null;
        }

        return this._gl.getShaderSource(shaders[0]);
    }

    /**
     * Gets the source code of the fragment shader associated with a specific webGL program
     * @param program defines the program to use
     * @returns a string containing the source code of the fragment shader associated with the program
     */
    public getFragmentShaderSource(program: WebGLProgram): Nullable<string> {
        var shaders = this._gl.getAttachedShaders(program);

        if (!shaders) {
            return null;
        }

        return this._gl.getShaderSource(shaders[1]);
    }

    /**
     * Get the current error code of the webGL context
     * @returns the error code
     * @see https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/getError
     */
    public getError(): number {
        return this._gl.getError();
    }

    // FPS

    /**
     * Gets the current framerate
     * @returns a number representing the framerate
     */
    public getFps(): number {
        return this._fps;
    }

    /**
     * Gets the time spent between current and previous frame
     * @returns a number representing the delta time in ms
     */
    public getDeltaTime(): number {
        return this._deltaTime;
    }

    private _measureFps(): void {
        this._performanceMonitor.sampleFrame();
        this._fps = this._performanceMonitor.averageFPS;
        this._deltaTime = this._performanceMonitor.instantaneousFrameTime || 0;
    }

    /** @hidden */
    public _readTexturePixels(texture: InternalTexture, width: number, height: number, faceIndex = -1, level = 0, buffer: Nullable<ArrayBufferView> = null): ArrayBufferView {
        let gl = this._gl;
        if (!this._dummyFramebuffer) {
            let dummy = gl.createFramebuffer();

            if (!dummy) {
                throw new Error("Unable to create dummy framebuffer");
            }

            this._dummyFramebuffer = dummy;
        }
        gl.bindFramebuffer(gl.FRAMEBUFFER, this._dummyFramebuffer);

        if (faceIndex > -1) {
            gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_CUBE_MAP_POSITIVE_X + faceIndex, texture._webGLTexture, level);
        } else {
            gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture._webGLTexture, level);
        }

        let readType = (texture.type !== undefined) ? this._getWebGLTextureType(texture.type) : gl.UNSIGNED_BYTE;

        switch (readType) {
            case gl.UNSIGNED_BYTE:
                if (!buffer) {
                    buffer = new Uint8Array(4 * width * height);
                }
                readType = gl.UNSIGNED_BYTE;
                break;
            default:
                if (!buffer) {
                    buffer = new Float32Array(4 * width * height);
                }
                readType = gl.FLOAT;
                break;
        }

        gl.readPixels(0, 0, width, height, gl.RGBA, readType, <DataView>buffer);
        gl.bindFramebuffer(gl.FRAMEBUFFER, this._currentFramebuffer);

        return buffer;
    }

    private _canRenderToFloatFramebuffer(): boolean {
        if (this._webGLVersion > 1) {
            return this._caps.colorBufferFloat;
        }
        return this._canRenderToFramebuffer(Engine.TEXTURETYPE_FLOAT);
    }

    private _canRenderToHalfFloatFramebuffer(): boolean {
        if (this._webGLVersion > 1) {
            return this._caps.colorBufferFloat;
        }
        return this._canRenderToFramebuffer(Engine.TEXTURETYPE_HALF_FLOAT);
    }

    // Thank you : http://stackoverflow.com/questions/28827511/webgl-ios-render-to-floating-point-texture
    private _canRenderToFramebuffer(type: number): boolean {
        let gl = this._gl;

        //clear existing errors
        while (gl.getError() !== gl.NO_ERROR) { }

        let successful = true;

        let texture = gl.createTexture();
        gl.bindTexture(gl.TEXTURE_2D, texture);
        gl.texImage2D(gl.TEXTURE_2D, 0, this._getRGBABufferInternalSizedFormat(type), 1, 1, 0, gl.RGBA, this._getWebGLTextureType(type), null);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);

        let fb = gl.createFramebuffer();
        gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
        gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
        let status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);

        successful = successful && (status === gl.FRAMEBUFFER_COMPLETE);
        successful = successful && (gl.getError() === gl.NO_ERROR);

        //try render by clearing frame buffer's color buffer
        if (successful) {
            gl.clear(gl.COLOR_BUFFER_BIT);
            successful = successful && (gl.getError() === gl.NO_ERROR);
        }

        //try reading from frame to ensure render occurs (just creating the FBO is not sufficient to determine if rendering is supported)
        if (successful) {
            //in practice it's sufficient to just read from the backbuffer rather than handle potentially issues reading from the texture
            gl.bindFramebuffer(gl.FRAMEBUFFER, null);
            let readFormat = gl.RGBA;
            let readType = gl.UNSIGNED_BYTE;
            let buffer = new Uint8Array(4);
            gl.readPixels(0, 0, 1, 1, readFormat, readType, buffer);
            successful = successful && (gl.getError() === gl.NO_ERROR);
        }

        //clean up
        gl.deleteTexture(texture);
        gl.deleteFramebuffer(fb);
        gl.bindFramebuffer(gl.FRAMEBUFFER, null);

        //clear accumulated errors
        while (!successful && (gl.getError() !== gl.NO_ERROR)) { }

        return successful;
    }

    /** @hidden */
    public _getWebGLTextureType(type: number): number {
        if (this._webGLVersion === 1) {
            switch (type) {
                case Engine.TEXTURETYPE_FLOAT:
                    return this._gl.FLOAT;
                case Engine.TEXTURETYPE_HALF_FLOAT:
                    return this._gl.HALF_FLOAT_OES;
                case Engine.TEXTURETYPE_UNSIGNED_BYTE:
                    return this._gl.UNSIGNED_BYTE;
            }
            return this._gl.UNSIGNED_BYTE;
        }

        switch (type) {
            case Engine.TEXTURETYPE_BYTE:
                return this._gl.BYTE;
            case Engine.TEXTURETYPE_UNSIGNED_BYTE:
                return this._gl.UNSIGNED_BYTE;
            case Engine.TEXTURETYPE_SHORT:
                return this._gl.SHORT;
            case Engine.TEXTURETYPE_UNSIGNED_SHORT:
                return this._gl.UNSIGNED_SHORT;
            case Engine.TEXTURETYPE_INT:
                return this._gl.INT;
            case Engine.TEXTURETYPE_UNSIGNED_INTEGER: // Refers to UNSIGNED_INT
                return this._gl.UNSIGNED_INT;
            case Engine.TEXTURETYPE_FLOAT:
                return this._gl.FLOAT;
            case Engine.TEXTURETYPE_HALF_FLOAT:
                return this._gl.HALF_FLOAT;
            case Engine.TEXTURETYPE_UNSIGNED_SHORT_4_4_4_4:
                return this._gl.UNSIGNED_SHORT_4_4_4_4;
            case Engine.TEXTURETYPE_UNSIGNED_SHORT_5_5_5_1:
                return this._gl.UNSIGNED_SHORT_5_5_5_1;
            case Engine.TEXTURETYPE_UNSIGNED_SHORT_5_6_5:
                return this._gl.UNSIGNED_SHORT_5_6_5;
            case Engine.TEXTURETYPE_UNSIGNED_INT_2_10_10_10_REV:
                return this._gl.UNSIGNED_INT_2_10_10_10_REV;
            case Engine.TEXTURETYPE_UNSIGNED_INT_24_8:
                return this._gl.UNSIGNED_INT_24_8;
            case Engine.TEXTURETYPE_UNSIGNED_INT_10F_11F_11F_REV:
                return this._gl.UNSIGNED_INT_10F_11F_11F_REV;
            case Engine.TEXTURETYPE_UNSIGNED_INT_5_9_9_9_REV:
                return this._gl.UNSIGNED_INT_5_9_9_9_REV;
            case Engine.TEXTURETYPE_FLOAT_32_UNSIGNED_INT_24_8_REV:
                return this._gl.FLOAT_32_UNSIGNED_INT_24_8_REV;
        }

        return this._gl.UNSIGNED_BYTE;
    }

    private _getInternalFormat(format: number): number {
        var internalFormat = this._gl.RGBA;

        switch (format) {
            case Engine.TEXTUREFORMAT_ALPHA:
                internalFormat = this._gl.ALPHA;
                break;
            case Engine.TEXTUREFORMAT_LUMINANCE:
                internalFormat = this._gl.LUMINANCE;
                break;
            case Engine.TEXTUREFORMAT_LUMINANCE_ALPHA:
                internalFormat = this._gl.LUMINANCE_ALPHA;
                break;
            case Engine.TEXTUREFORMAT_RED:
                internalFormat = this._gl.RED;
                break;
            case Engine.TEXTUREFORMAT_RG:
                internalFormat = this._gl.RG;
                break;
            case Engine.TEXTUREFORMAT_RGB:
                internalFormat = this._gl.RGB;
                break;
            case Engine.TEXTUREFORMAT_RGBA:
                internalFormat = this._gl.RGBA;
                break;
        }

        if (this._webGLVersion > 1) {
            switch (format) {
                case Engine.TEXTUREFORMAT_RED_INTEGER:
                    internalFormat = this._gl.RED_INTEGER;
                    break;
                case Engine.TEXTUREFORMAT_RG_INTEGER:
                    internalFormat = this._gl.RG_INTEGER;
                    break;
                case Engine.TEXTUREFORMAT_RGB_INTEGER:
                    internalFormat = this._gl.RGB_INTEGER;
                    break;
                case Engine.TEXTUREFORMAT_RGBA_INTEGER:
                    internalFormat = this._gl.RGBA_INTEGER;
                    break;
            }
        }

        return internalFormat;
    }

    /** @hidden */
    public _getRGBABufferInternalSizedFormat(type: number, format?: number): number {
        if (this._webGLVersion === 1) {
            if (format !== undefined) {
                switch (format) {
                    case Engine.TEXTUREFORMAT_ALPHA:
                        return this._gl.ALPHA;
                    case Engine.TEXTUREFORMAT_LUMINANCE:
                        return this._gl.LUMINANCE;
                    case Engine.TEXTUREFORMAT_LUMINANCE_ALPHA:
                        return this._gl.LUMINANCE_ALPHA;
                }
            }
            return this._gl.RGBA;
        }

        switch (type) {
            case Engine.TEXTURETYPE_BYTE:
                switch (format) {
                    case Engine.TEXTUREFORMAT_RED:
                        return this._gl.R8_SNORM;
                    case Engine.TEXTUREFORMAT_RG:
                        return this._gl.RG8_SNORM;
                    case Engine.TEXTUREFORMAT_RGB:
                        return this._gl.RGB8_SNORM;
                    case Engine.TEXTUREFORMAT_RED_INTEGER:
                        return this._gl.R8I;
                    case Engine.TEXTUREFORMAT_RG_INTEGER:
                        return this._gl.RG8I;
                    case Engine.TEXTUREFORMAT_RGB_INTEGER:
                        return this._gl.RGB8I;
                    case Engine.TEXTUREFORMAT_RGBA_INTEGER:
                        return this._gl.RGBA8I;
                    default:
                        return this._gl.RGBA8_SNORM;
                }
            case Engine.TEXTURETYPE_UNSIGNED_BYTE:
                switch (format) {
                    case Engine.TEXTUREFORMAT_RED:
                        return this._gl.R8;
                    case Engine.TEXTUREFORMAT_RG:
                        return this._gl.RG8;
                    case Engine.TEXTUREFORMAT_RGB:
                        return this._gl.RGB8; // By default. Other possibilities are RGB565, SRGB8.
                    case Engine.TEXTUREFORMAT_RGBA:
                        return this._gl.RGBA8; // By default. Other possibilities are RGB5_A1, RGBA4, SRGB8_ALPHA8.
                    case Engine.TEXTUREFORMAT_RED_INTEGER:
                        return this._gl.R8UI;
                    case Engine.TEXTUREFORMAT_RG_INTEGER:
                        return this._gl.RG8UI;
                    case Engine.TEXTUREFORMAT_RGB_INTEGER:
                        return this._gl.RGB8UI;
                    case Engine.TEXTUREFORMAT_RGBA_INTEGER:
                        return this._gl.RGBA8UI;
                    default:
                        return this._gl.RGBA8;
                }
            case Engine.TEXTURETYPE_SHORT:
                switch (format) {
                    case Engine.TEXTUREFORMAT_RED_INTEGER:
                        return this._gl.R16I;
                    case Engine.TEXTUREFORMAT_RG_INTEGER:
                        return this._gl.RG16I;
                    case Engine.TEXTUREFORMAT_RGB_INTEGER:
                        return this._gl.RGB16I;
                    case Engine.TEXTUREFORMAT_RGBA_INTEGER:
                        return this._gl.RGBA16I;
                    default:
                        return this._gl.RGBA16I;
                }
            case Engine.TEXTURETYPE_UNSIGNED_SHORT:
                switch (format) {
                    case Engine.TEXTUREFORMAT_RED_INTEGER:
                        return this._gl.R16UI;
                    case Engine.TEXTUREFORMAT_RG_INTEGER:
                        return this._gl.RG16UI;
                    case Engine.TEXTUREFORMAT_RGB_INTEGER:
                        return this._gl.RGB16UI;
                    case Engine.TEXTUREFORMAT_RGBA_INTEGER:
                        return this._gl.RGBA16UI;
                    default:
                        return this._gl.RGBA16UI;
                }
            case Engine.TEXTURETYPE_INT:
                switch (format) {
                    case Engine.TEXTUREFORMAT_RED_INTEGER:
                        return this._gl.R32I;
                    case Engine.TEXTUREFORMAT_RG_INTEGER:
                        return this._gl.RG32I;
                    case Engine.TEXTUREFORMAT_RGB_INTEGER:
                        return this._gl.RGB32I;
                    case Engine.TEXTUREFORMAT_RGBA_INTEGER:
                        return this._gl.RGBA32I;
                    default:
                        return this._gl.RGBA32I;
                }
            case Engine.TEXTURETYPE_UNSIGNED_INTEGER: // Refers to UNSIGNED_INT
                switch (format) {
                    case Engine.TEXTUREFORMAT_RED_INTEGER:
                        return this._gl.R32UI;
                    case Engine.TEXTUREFORMAT_RG_INTEGER:
                        return this._gl.RG32UI;
                    case Engine.TEXTUREFORMAT_RGB_INTEGER:
                        return this._gl.RGB32UI;
                    case Engine.TEXTUREFORMAT_RGBA_INTEGER:
                        return this._gl.RGBA32UI;
                    default:
                        return this._gl.RGBA32UI;
                }
            case Engine.TEXTURETYPE_FLOAT:
                switch (format) {
                    case Engine.TEXTUREFORMAT_RED:
                        return this._gl.R32F; // By default. Other possibility is R16F.
                    case Engine.TEXTUREFORMAT_RG:
                        return this._gl.RG32F; // By default. Other possibility is RG16F.
                    case Engine.TEXTUREFORMAT_RGB:
                        return this._gl.RGB32F; // By default. Other possibilities are RGB16F, R11F_G11F_B10F, RGB9_E5.
                    case Engine.TEXTUREFORMAT_RGBA:
                        return this._gl.RGBA32F; // By default. Other possibility is RGBA16F.
                    default:
                        return this._gl.RGBA32F;
                }
            case Engine.TEXTURETYPE_HALF_FLOAT:
                switch (format) {
                    case Engine.TEXTUREFORMAT_RED:
                        return this._gl.R16F;
                    case Engine.TEXTUREFORMAT_RG:
                        return this._gl.RG16F;
                    case Engine.TEXTUREFORMAT_RGB:
                        return this._gl.RGB16F; // By default. Other possibilities are R11F_G11F_B10F, RGB9_E5.
                    case Engine.TEXTUREFORMAT_RGBA:
                        return this._gl.RGBA16F;
                    default:
                        return this._gl.RGBA16F;
                }
            case Engine.TEXTURETYPE_UNSIGNED_SHORT_5_6_5:
                return this._gl.RGB565;
            case Engine.TEXTURETYPE_UNSIGNED_INT_10F_11F_11F_REV:
                return this._gl.R11F_G11F_B10F;
            case Engine.TEXTURETYPE_UNSIGNED_INT_5_9_9_9_REV:
                return this._gl.RGB9_E5;
            case Engine.TEXTURETYPE_UNSIGNED_SHORT_4_4_4_4:
                return this._gl.RGBA4;
            case Engine.TEXTURETYPE_UNSIGNED_SHORT_5_5_5_1:
                return this._gl.RGB5_A1;
            case Engine.TEXTURETYPE_UNSIGNED_INT_2_10_10_10_REV:
                switch (format) {
                    case Engine.TEXTUREFORMAT_RGBA:
                        return this._gl.RGB10_A2; // By default. Other possibility is RGB5_A1.
                    case Engine.TEXTUREFORMAT_RGBA_INTEGER:
                        return this._gl.RGB10_A2UI;
                    default:
                        return this._gl.RGB10_A2;
                }
        }

        return this._gl.RGBA8;
    }

    /** @hidden */
    public _getRGBAMultiSampleBufferFormat(type: number): number {
        if (type === Engine.TEXTURETYPE_FLOAT) {
            return this._gl.RGBA32F;
        }
        else if (type === Engine.TEXTURETYPE_HALF_FLOAT) {
            return this._gl.RGBA16F;
        }

        return this._gl.RGBA8;
    }

    /** @hidden */
    public _loadFile(url: string, onSuccess: (data: string | ArrayBuffer, responseURL?: string) => void, onProgress?: (data: any) => void, offlineProvider?: IOfflineProvider, useArrayBuffer?: boolean, onError?: (request?: WebRequest, exception?: any) => void): IFileRequest {
        let request = Tools.LoadFile(url, onSuccess, onProgress, offlineProvider, useArrayBuffer, onError);
        this._activeRequests.push(request);
        request.onCompleteObservable.add((request) => {
            this._activeRequests.splice(this._activeRequests.indexOf(request), 1);
        });
        return request;
    }

    /** @hidden */
    public _loadFileAsync(url: string, offlineProvider?: IOfflineProvider, useArrayBuffer?: boolean): Promise<string | ArrayBuffer> {
        return new Promise((resolve, reject) => {
            this._loadFile(url, (data) => {
                resolve(data);
            }, undefined, offlineProvider, useArrayBuffer, (request, exception) => {
                reject(exception);
            });
        });
    }

    private _partialLoadFile(url: string, index: number, loadedFiles: (string | ArrayBuffer)[], onfinish: (files: (string | ArrayBuffer)[]) => void, onErrorCallBack: Nullable<(message?: string, exception?: any) => void> = null): void {
        var onload = (data: string | ArrayBuffer) => {
            loadedFiles[index] = data;
            (<any>loadedFiles)._internalCount++;

            if ((<any>loadedFiles)._internalCount === 6) {
                onfinish(loadedFiles);
            }
        };

        const onerror = (request?: WebRequest, exception?: any) => {
            if (onErrorCallBack && request) {
                onErrorCallBack(request.status + " " + request.statusText, exception);
            }
        };

        this._loadFile(url, onload, undefined, undefined, true, onerror);
    }

    private _cascadeLoadFiles(scene: Nullable<Scene>, onfinish: (images: (string | ArrayBuffer)[]) => void, files: string[], onError: Nullable<(message?: string, exception?: any) => void> = null): void {
        var loadedFiles: (string | ArrayBuffer)[] = [];
        (<any>loadedFiles)._internalCount = 0;

        for (let index = 0; index < 6; index++) {
            this._partialLoadFile(files[index], index, loadedFiles, onfinish, onError);
        }
    }

    // Statics

    /**
     * Gets a boolean indicating if the engine can be instanciated (ie. if a webGL context can be found)
     * @returns true if the engine can be created
     * @ignorenaming
     */
    public static isSupported(): boolean {
        try {
            var tempcanvas = document.createElement("canvas");
            var gl = tempcanvas.getContext("webgl") || tempcanvas.getContext("experimental-webgl");

            return gl != null && !!window.WebGLRenderingContext;
        } catch (e) {
            return false;
        }
    }
}