Babylon.js/src/Particles/particleSystem.ts

import { Nullable } from "../types";
import { IAnimatable } from "../Misc/tools";
import { FactorGradient, ColorGradient, Color3Gradient, GradientHelper } from "../Misc/gradients";
import { Observable, Observer } from "../Misc/observable";
import { Color4, Color3, Vector3, Matrix, Tmp, ISize, Vector4 } from "../Maths/math";
import { Scalar } from "../Maths/math.scalar";
import { VertexBuffer } from "../Meshes/buffer";
import { Buffer } from "../Meshes/buffer";
import { AbstractMesh } from "../Meshes/abstractMesh";
import { Material } from "../Materials/material";
import { MaterialHelper } from "../Materials/materialHelper";
import { Effect } from "../Materials/effect";
import { ImageProcessingConfiguration } from "../Materials/imageProcessingConfiguration";
import { Texture } from "../Materials/Textures/texture";
import { RawTexture } from "../Materials/Textures/rawTexture";
import { ProceduralTexture } from "../Materials/Textures/Procedurals/proceduralTexture";
import { EngineStore } from "../Engines/engineStore";
import { Scene, IDisposable } from "../scene";
import { BoxParticleEmitter, IParticleEmitterType, HemisphericParticleEmitter, SphereParticleEmitter, SphereDirectedParticleEmitter, CylinderParticleEmitter, ConeParticleEmitter } from "../Particles/EmitterTypes/index";
import { IParticleSystem } from "./IParticleSystem";
import { BaseParticleSystem } from "./baseParticleSystem";
import { Particle } from "./particle";
import { SubEmitter, SubEmitterType } from "./subEmitter";
import { Constants } from "../Engines/constants";
import { SerializationHelper } from "../Misc/decorators";
import { DeepCopier } from "../Misc/deepCopier";
import { _TypeStore } from '../Misc/typeStore';

import "../Shaders/particles.fragment";
import "../Shaders/particles.vertex";
import { DataBuffer } from '../Meshes/dataBuffer';

/**
 * This represents a particle system in Babylon.
 * Particles are often small sprites used to simulate hard-to-reproduce phenomena like fire, smoke, water, or abstract visual effects like magic glitter and faery dust.
 * Particles can take different shapes while emitted like box, sphere, cone or you can write your custom function.
 * @example https://doc.babylonjs.com/babylon101/particles
 */
export class ParticleSystem extends BaseParticleSystem implements IDisposable, IAnimatable, IParticleSystem {

    /**
     * Billboard mode will only apply to Y axis
     */
    public static readonly BILLBOARDMODE_Y = Constants.PARTICLES_BILLBOARDMODE_Y;
    /**
     * Billboard mode will apply to all axes
     */
    public static readonly BILLBOARDMODE_ALL = Constants.PARTICLES_BILLBOARDMODE_ALL;
    /**
     * Special billboard mode where the particle will be biilboard to the camera but rotated to align with direction
     */
    public static readonly BILLBOARDMODE_STRETCHED = Constants.PARTICLES_BILLBOARDMODE_STRETCHED;

    /**
     * This function can be defined to provide custom update for active particles.
     * This function will be called instead of regular update (age, position, color, etc.).
     * Do not forget that this function will be called on every frame so try to keep it simple and fast :)
     */
    public updateFunction: (particles: Particle[]) => void;

    private _emitterWorldMatrix: Matrix;

    /**
     * This function can be defined to specify initial direction for every new particle.
     * It by default use the emitterType defined function
     */
    public startDirectionFunction: (worldMatrix: Matrix, directionToUpdate: Vector3, particle: Particle) => void;
    /**
     * This function can be defined to specify initial position for every new particle.
     * It by default use the emitterType defined function
     */
    public startPositionFunction: (worldMatrix: Matrix, positionToUpdate: Vector3, particle: Particle) => void;

    /**
     * @hidden
     */
    public _inheritedVelocityOffset = new Vector3();
    /**
    * An event triggered when the system is disposed
    */
    public onDisposeObservable = new Observable<ParticleSystem>();

    private _onDisposeObserver: Nullable<Observer<ParticleSystem>>;
    /**
     * Sets a callback that will be triggered when the system is disposed
     */
    public set onDispose(callback: () => void) {
        if (this._onDisposeObserver) {
            this.onDisposeObservable.remove(this._onDisposeObserver);
        }
        this._onDisposeObserver = this.onDisposeObservable.add(callback);
    }

    private _particles = new Array<Particle>();
    private _epsilon: number;
    private _capacity: number;
    private _stockParticles = new Array<Particle>();
    private _newPartsExcess = 0;
    private _vertexData: Float32Array;
    private _vertexBuffer: Nullable<Buffer>;
    private _vertexBuffers: { [key: string]: VertexBuffer } = {};
    private _spriteBuffer: Nullable<Buffer>;
    private _indexBuffer: Nullable<DataBuffer>;
    private _effect: Effect;
    private _customEffect: Nullable<Effect>;
    private _cachedDefines: string;
    private _scaledColorStep = new Color4(0, 0, 0, 0);
    private _colorDiff = new Color4(0, 0, 0, 0);
    private _scaledDirection = Vector3.Zero();
    private _scaledGravity = Vector3.Zero();
    private _currentRenderId = -1;
    private _alive: boolean;
    private _useInstancing = false;

    private _started = false;
    private _stopped = false;
    private _actualFrame = 0;
    private _scaledUpdateSpeed: number;
    private _vertexBufferSize: number;

    /** @hidden */
    public _currentEmitRateGradient: Nullable<FactorGradient>;
    /** @hidden */
    public _currentEmitRate1 = 0;
    /** @hidden */
    public _currentEmitRate2 = 0;

    /** @hidden */
    public _currentStartSizeGradient: Nullable<FactorGradient>;
    /** @hidden */
    public _currentStartSize1 = 0;
    /** @hidden */
    public _currentStartSize2 = 0;

    private readonly _rawTextureWidth = 256;
    private _rampGradientsTexture: Nullable<RawTexture>;
    private _useRampGradients = false;

    /** Gets or sets a boolean indicating that ramp gradients must be used
     * @see http://doc.babylonjs.com/babylon101/particles#ramp-gradients
     */
    public get useRampGradients(): boolean {
        return this._useRampGradients;
    }

    public set useRampGradients(value: boolean) {
        if (this._useRampGradients === value) {
            return;
        }

        this._useRampGradients = value;

        this._resetEffect();
    }

    // Sub-emitters
    /**
     * The Sub-emitters templates that will be used to generate the sub particle system to be associated with the system, this property is used by the root particle system only.
     * When a particle is spawned, an array will be chosen at random and all the emitters in that array will be attached to the particle.  (Default: [])
     */
    public subEmitters: Array<ParticleSystem | SubEmitter | Array<SubEmitter>>;
    // the subEmitters field above converted to a constant type
    private _subEmitters: Array<Array<SubEmitter>>;
    /**
     * @hidden
     * If the particle systems emitter should be disposed when the particle system is disposed
     */
    public _disposeEmitterOnDispose = false;
    /**
    * The current active Sub-systems, this property is used by the root particle system only.
    */
    public activeSubSystems: Array<ParticleSystem>;

    private _rootParticleSystem: Nullable<ParticleSystem>;
    //end of Sub-emitter

    /**
     * Gets the current list of active particles
     */
    public get particles(): Particle[] {
        return this._particles;
    }

    /**
     * Returns the string "ParticleSystem"
     * @returns a string containing the class name
     */
    public getClassName(): string {
        return "ParticleSystem";
    }

    /**
     * Instantiates a particle system.
     * Particles are often small sprites used to simulate hard-to-reproduce phenomena like fire, smoke, water, or abstract visual effects like magic glitter and faery dust.
     * @param name The name of the particle system
     * @param capacity The max number of particles alive at the same time
     * @param scene The scene the particle system belongs to
     * @param customEffect a custom effect used to change the way particles are rendered by default
     * @param isAnimationSheetEnabled Must be true if using a spritesheet to animate the particles texture
     * @param epsilon Offset used to render the particles
     */
    constructor(name: string, capacity: number, scene: Scene, customEffect: Nullable<Effect> = null, isAnimationSheetEnabled: boolean = false, epsilon: number = 0.01) {
        super(name);

        this._capacity = capacity;

        this._epsilon = epsilon;
        this._isAnimationSheetEnabled = isAnimationSheetEnabled;

        this._scene = scene || EngineStore.LastCreatedScene;

        // Setup the default processing configuration to the scene.
        this._attachImageProcessingConfiguration(null);

        this._customEffect = customEffect;

        this._scene.particleSystems.push(this);

        this._useInstancing = this._scene.getEngine().getCaps().instancedArrays;

        this._createIndexBuffer();
        this._createVertexBuffers();

        // Default emitter type
        this.particleEmitterType = new BoxParticleEmitter();

        // Update
        this.updateFunction = (particles: Particle[]): void => {
            let noiseTextureSize: Nullable<ISize> = null;
            let noiseTextureData: Nullable<Uint8Array> = null;

            if (this.noiseTexture) { // We need to get texture data back to CPU
                noiseTextureSize = this.noiseTexture.getSize();
                noiseTextureData = <Nullable<Uint8Array>>(this.noiseTexture.getContent());
            }

            for (var index = 0; index < particles.length; index++) {
                var particle = particles[index];

                let scaledUpdateSpeed = this._scaledUpdateSpeed;
                let previousAge = particle.age;
                particle.age += scaledUpdateSpeed;

                // Evaluate step to death
                if (particle.age > particle.lifeTime) {
                    let diff = particle.age - previousAge;
                    let oldDiff = particle.lifeTime - previousAge;

                    scaledUpdateSpeed = (oldDiff * scaledUpdateSpeed) / diff;

                    particle.age = particle.lifeTime;
                }

                let ratio = particle.age / particle.lifeTime;

                // Color
                if (this._colorGradients && this._colorGradients.length > 0) {
                    GradientHelper.GetCurrentGradient(ratio, this._colorGradients, (currentGradient, nextGradient, scale) => {
                        if (currentGradient !== particle._currentColorGradient) {
                            particle._currentColor1.copyFrom(particle._currentColor2);
                            (<ColorGradient>nextGradient).getColorToRef(particle._currentColor2);
                            particle._currentColorGradient = (<ColorGradient>currentGradient);
                        }
                        Color4.LerpToRef(particle._currentColor1, particle._currentColor2, scale, particle.color);
                    });
                }
                else {
                    particle.colorStep.scaleToRef(scaledUpdateSpeed, this._scaledColorStep);
                    particle.color.addInPlace(this._scaledColorStep);

                    if (particle.color.a < 0) {
                        particle.color.a = 0;
                    }
                }

                // Angular speed
                if (this._angularSpeedGradients && this._angularSpeedGradients.length > 0) {
                    GradientHelper.GetCurrentGradient(ratio, this._angularSpeedGradients, (currentGradient, nextGradient, scale) => {
                        if (currentGradient !== particle._currentAngularSpeedGradient) {
                            particle._currentAngularSpeed1 = particle._currentAngularSpeed2;
                            particle._currentAngularSpeed2 = (<FactorGradient>nextGradient).getFactor();
                            particle._currentAngularSpeedGradient = (<FactorGradient>currentGradient);
                        }
                        particle.angularSpeed = Scalar.Lerp(particle._currentAngularSpeed1, particle._currentAngularSpeed2, scale);
                    });
                }
                particle.angle += particle.angularSpeed * scaledUpdateSpeed;

                // Direction
                let directionScale = scaledUpdateSpeed;

                /// Velocity
                if (this._velocityGradients && this._velocityGradients.length > 0) {
                    GradientHelper.GetCurrentGradient(ratio, this._velocityGradients, (currentGradient, nextGradient, scale) => {
                        if (currentGradient !== particle._currentVelocityGradient) {
                            particle._currentVelocity1 = particle._currentVelocity2;
                            particle._currentVelocity2 = (<FactorGradient>nextGradient).getFactor();
                            particle._currentVelocityGradient = (<FactorGradient>currentGradient);
                        }
                        directionScale *= Scalar.Lerp(particle._currentVelocity1, particle._currentVelocity2, scale);
                    });
                }

                particle.direction.scaleToRef(directionScale, this._scaledDirection);

                /// Limit velocity
                if (this._limitVelocityGradients && this._limitVelocityGradients.length > 0) {
                    GradientHelper.GetCurrentGradient(ratio, this._limitVelocityGradients, (currentGradient, nextGradient, scale) => {
                        if (currentGradient !== particle._currentLimitVelocityGradient) {
                            particle._currentLimitVelocity1 = particle._currentLimitVelocity2;
                            particle._currentLimitVelocity2 = (<FactorGradient>nextGradient).getFactor();
                            particle._currentLimitVelocityGradient = (<FactorGradient>currentGradient);
                        }

                        let limitVelocity = Scalar.Lerp(particle._currentLimitVelocity1, particle._currentLimitVelocity2, scale);
                        let currentVelocity = particle.direction.length();

                        if (currentVelocity > limitVelocity) {
                            particle.direction.scaleInPlace(this.limitVelocityDamping);
                        }
                    });
                }

                /// Drag
                if (this._dragGradients && this._dragGradients.length > 0) {
                    GradientHelper.GetCurrentGradient(ratio, this._dragGradients, (currentGradient, nextGradient, scale) => {
                        if (currentGradient !== particle._currentDragGradient) {
                            particle._currentDrag1 = particle._currentDrag2;
                            particle._currentDrag2 = (<FactorGradient>nextGradient).getFactor();
                            particle._currentDragGradient = (<FactorGradient>currentGradient);
                        }

                        let drag = Scalar.Lerp(particle._currentDrag1, particle._currentDrag2, scale);

                        this._scaledDirection.scaleInPlace(1.0 - drag);
                    });
                }

                particle.position.addInPlace(this._scaledDirection);

                // Noise
                if (noiseTextureData && noiseTextureSize && particle._randomNoiseCoordinates1) {
                    let fetchedColorR = this._fetchR(particle._randomNoiseCoordinates1.x, particle._randomNoiseCoordinates1.y, noiseTextureSize.width, noiseTextureSize.height, noiseTextureData);
                    let fetchedColorG = this._fetchR(particle._randomNoiseCoordinates1.z, particle._randomNoiseCoordinates2.x, noiseTextureSize.width, noiseTextureSize.height, noiseTextureData);
                    let fetchedColorB = this._fetchR(particle._randomNoiseCoordinates2.y, particle._randomNoiseCoordinates2.z, noiseTextureSize.width, noiseTextureSize.height, noiseTextureData);

                    let force = Tmp.Vector3[0];
                    let scaledForce = Tmp.Vector3[1];

                    force.copyFromFloats((2 * fetchedColorR - 1) * this.noiseStrength.x, (2 * fetchedColorG - 1) * this.noiseStrength.y, (2 * fetchedColorB - 1) * this.noiseStrength.z);

                    force.scaleToRef(scaledUpdateSpeed, scaledForce);
                    particle.direction.addInPlace(scaledForce);
                }

                // Gravity
                this.gravity.scaleToRef(scaledUpdateSpeed, this._scaledGravity);
                particle.direction.addInPlace(this._scaledGravity);

                // Size
                if (this._sizeGradients && this._sizeGradients.length > 0) {
                    GradientHelper.GetCurrentGradient(ratio, this._sizeGradients, (currentGradient, nextGradient, scale) => {
                        if (currentGradient !== particle._currentSizeGradient) {
                            particle._currentSize1 = particle._currentSize2;
                            particle._currentSize2 = (<FactorGradient>nextGradient).getFactor();
                            particle._currentSizeGradient = (<FactorGradient>currentGradient);
                        }
                        particle.size = Scalar.Lerp(particle._currentSize1, particle._currentSize2, scale);
                    });
                }

                // Remap data
                if (this._useRampGradients) {
                    if (this._colorRemapGradients && this._colorRemapGradients.length > 0) {
                        GradientHelper.GetCurrentGradient(ratio, this._colorRemapGradients, (currentGradient, nextGradient, scale) => {
                            let min = Scalar.Lerp((<FactorGradient>currentGradient).factor1, (<FactorGradient>nextGradient).factor1, scale);
                            let max = Scalar.Lerp((<FactorGradient>currentGradient).factor2!, (<FactorGradient>nextGradient).factor2!, scale);

                            particle.remapData.x = min;
                            particle.remapData.y = max - min;
                        });
                    }

                    if (this._alphaRemapGradients && this._alphaRemapGradients.length > 0) {
                        GradientHelper.GetCurrentGradient(ratio, this._alphaRemapGradients, (currentGradient, nextGradient, scale) => {
                            let min = Scalar.Lerp((<FactorGradient>currentGradient).factor1, (<FactorGradient>nextGradient).factor1, scale);
                            let max = Scalar.Lerp((<FactorGradient>currentGradient).factor2!, (<FactorGradient>nextGradient).factor2!, scale);

                            particle.remapData.z = min;
                            particle.remapData.w = max - min;
                        });
                    }
                }

                if (this._isAnimationSheetEnabled) {
                    particle.updateCellIndex();
                }

                // Update the position of the attached sub-emitters to match their attached particle
                particle._inheritParticleInfoToSubEmitters();

                if (particle.age >= particle.lifeTime) { // Recycle by swapping with last particle
                    this._emitFromParticle(particle);
                    if (particle._attachedSubEmitters) {
                        particle._attachedSubEmitters.forEach((subEmitter) => {
                            subEmitter.particleSystem.disposeOnStop = true;
                            subEmitter.particleSystem.stop();
                        });
                        particle._attachedSubEmitters = null;
                    }
                    this.recycleParticle(particle);
                    index--;
                    continue;
                }
            }
        };
    }

    private _addFactorGradient(factorGradients: FactorGradient[], gradient: number, factor: number, factor2?: number) {
        let newGradient = new FactorGradient();
        newGradient.gradient = gradient;
        newGradient.factor1 = factor;
        newGradient.factor2 = factor2;
        factorGradients.push(newGradient);

        factorGradients.sort((a, b) => {
            if (a.gradient < b.gradient) {
                return -1;
            } else if (a.gradient > b.gradient) {
                return 1;
            }

            return 0;
        });
    }

    private _removeFactorGradient(factorGradients: Nullable<FactorGradient[]>, gradient: number) {
        if (!factorGradients) {
            return;
        }

        let index = 0;
        for (var factorGradient of factorGradients) {
            if (factorGradient.gradient === gradient) {
                factorGradients.splice(index, 1);
                break;
            }
            index++;
        }
    }

    /**
     * Adds a new life time gradient
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param factor defines the life time factor to affect to the specified gradient
     * @param factor2 defines an additional factor used to define a range ([factor, factor2]) with main value to pick the final value from
     * @returns the current particle system
     */
    public addLifeTimeGradient(gradient: number, factor: number, factor2?: number): IParticleSystem {
        if (!this._lifeTimeGradients) {
            this._lifeTimeGradients = [];
        }

        this._addFactorGradient(this._lifeTimeGradients, gradient, factor, factor2);

        return this;
    }

    /**
     * Remove a specific life time gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeLifeTimeGradient(gradient: number): IParticleSystem {
        this._removeFactorGradient(this._lifeTimeGradients, gradient);

        return this;
    }

    /**
     * Adds a new size gradient
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param factor defines the size factor to affect to the specified gradient
     * @param factor2 defines an additional factor used to define a range ([factor, factor2]) with main value to pick the final value from
     * @returns the current particle system
     */
    public addSizeGradient(gradient: number, factor: number, factor2?: number): IParticleSystem {
        if (!this._sizeGradients) {
            this._sizeGradients = [];
        }

        this._addFactorGradient(this._sizeGradients, gradient, factor, factor2);

        return this;
    }

    /**
     * Remove a specific size gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeSizeGradient(gradient: number): IParticleSystem {
        this._removeFactorGradient(this._sizeGradients, gradient);

        return this;
    }

    /**
     * Adds a new color remap gradient
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param min defines the color remap minimal range
     * @param max defines the color remap maximal range
     * @returns the current particle system
     */
    public addColorRemapGradient(gradient: number, min: number, max: number): IParticleSystem {
        if (!this._colorRemapGradients) {
            this._colorRemapGradients = [];
        }

        this._addFactorGradient(this._colorRemapGradients, gradient, min, max);

        return this;
    }

    /**
     * Remove a specific color remap gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeColorRemapGradient(gradient: number): IParticleSystem {
        this._removeFactorGradient(this._colorRemapGradients, gradient);

        return this;
    }

    /**
     * Adds a new alpha remap gradient
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param min defines the alpha remap minimal range
     * @param max defines the alpha remap maximal range
     * @returns the current particle system
     */
    public addAlphaRemapGradient(gradient: number, min: number, max: number): IParticleSystem {
        if (!this._alphaRemapGradients) {
            this._alphaRemapGradients = [];
        }

        this._addFactorGradient(this._alphaRemapGradients, gradient, min, max);

        return this;
    }

    /**
     * Remove a specific alpha remap gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeAlphaRemapGradient(gradient: number): IParticleSystem {
        this._removeFactorGradient(this._alphaRemapGradients, gradient);

        return this;
    }

    /**
     * Adds a new angular speed gradient
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param factor defines the angular speed  to affect to the specified gradient
     * @param factor2 defines an additional factor used to define a range ([factor, factor2]) with main value to pick the final value from
     * @returns the current particle system
     */
    public addAngularSpeedGradient(gradient: number, factor: number, factor2?: number): IParticleSystem {
        if (!this._angularSpeedGradients) {
            this._angularSpeedGradients = [];
        }

        this._addFactorGradient(this._angularSpeedGradients, gradient, factor, factor2);

        return this;
    }

    /**
     * Remove a specific angular speed gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeAngularSpeedGradient(gradient: number): IParticleSystem {
        this._removeFactorGradient(this._angularSpeedGradients, gradient);

        return this;
    }

    /**
     * Adds a new velocity gradient
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param factor defines the velocity to affect to the specified gradient
     * @param factor2 defines an additional factor used to define a range ([factor, factor2]) with main value to pick the final value from
     * @returns the current particle system
     */
    public addVelocityGradient(gradient: number, factor: number, factor2?: number): IParticleSystem {
        if (!this._velocityGradients) {
            this._velocityGradients = [];
        }

        this._addFactorGradient(this._velocityGradients, gradient, factor, factor2);

        return this;
    }

    /**
     * Remove a specific velocity gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeVelocityGradient(gradient: number): IParticleSystem {
        this._removeFactorGradient(this._velocityGradients, gradient);

        return this;
    }

    /**
     * Adds a new limit velocity gradient
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param factor defines the limit velocity value to affect to the specified gradient
     * @param factor2 defines an additional factor used to define a range ([factor, factor2]) with main value to pick the final value from
     * @returns the current particle system
     */
    public addLimitVelocityGradient(gradient: number, factor: number, factor2?: number): IParticleSystem {
        if (!this._limitVelocityGradients) {
            this._limitVelocityGradients = [];
        }

        this._addFactorGradient(this._limitVelocityGradients, gradient, factor, factor2);

        return this;
    }

    /**
     * Remove a specific limit velocity gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeLimitVelocityGradient(gradient: number): IParticleSystem {
        this._removeFactorGradient(this._limitVelocityGradients, gradient);

        return this;
    }

    /**
     * Adds a new drag gradient
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param factor defines the drag value to affect to the specified gradient
     * @param factor2 defines an additional factor used to define a range ([factor, factor2]) with main value to pick the final value from
     * @returns the current particle system
     */
    public addDragGradient(gradient: number, factor: number, factor2?: number): IParticleSystem {
        if (!this._dragGradients) {
            this._dragGradients = [];
        }

        this._addFactorGradient(this._dragGradients, gradient, factor, factor2);

        return this;
    }

    /**
     * Remove a specific drag gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeDragGradient(gradient: number): IParticleSystem {
        this._removeFactorGradient(this._dragGradients, gradient);

        return this;
    }

    /**
     * Adds a new emit rate gradient (please note that this will only work if you set the targetStopDuration property)
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param factor defines the emit rate value to affect to the specified gradient
     * @param factor2 defines an additional factor used to define a range ([factor, factor2]) with main value to pick the final value from
     * @returns the current particle system
     */
    public addEmitRateGradient(gradient: number, factor: number, factor2?: number): IParticleSystem {
        if (!this._emitRateGradients) {
            this._emitRateGradients = [];
        }

        this._addFactorGradient(this._emitRateGradients, gradient, factor, factor2);
        return this;
    }

    /**
     * Remove a specific emit rate gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeEmitRateGradient(gradient: number): IParticleSystem {
        this._removeFactorGradient(this._emitRateGradients, gradient);

        return this;
    }

    /**
     * Adds a new start size gradient (please note that this will only work if you set the targetStopDuration property)
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param factor defines the start size value to affect to the specified gradient
     * @param factor2 defines an additional factor used to define a range ([factor, factor2]) with main value to pick the final value from
     * @returns the current particle system
     */
    public addStartSizeGradient(gradient: number, factor: number, factor2?: number): IParticleSystem {
        if (!this._startSizeGradients) {
            this._startSizeGradients = [];
        }

        this._addFactorGradient(this._startSizeGradients, gradient, factor, factor2);
        return this;
    }

    /**
     * Remove a specific start size gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeStartSizeGradient(gradient: number): IParticleSystem {
        this._removeFactorGradient(this._emitRateGradients, gradient);

        return this;
    }

    private _createRampGradientTexture() {
        if (!this._rampGradients || !this._rampGradients.length || this._rampGradientsTexture) {
            return;
        }

        let data = new Uint8Array(this._rawTextureWidth * 4);
        let tmpColor = Tmp.Color3[0];

        for (var x = 0; x < this._rawTextureWidth; x++) {
            var ratio = x / this._rawTextureWidth;

            GradientHelper.GetCurrentGradient(ratio, this._rampGradients, (currentGradient, nextGradient, scale) => {

                Color3.LerpToRef((<Color3Gradient>currentGradient).color, (<Color3Gradient>nextGradient).color, scale, tmpColor);
                data[x * 4] = tmpColor.r * 255;
                data[x * 4 + 1] = tmpColor.g * 255;
                data[x * 4 + 2] = tmpColor.b * 255;
                data[x * 4 + 3] = 255;
            });

        }

        this._rampGradientsTexture = RawTexture.CreateRGBATexture(data, this._rawTextureWidth, 1, this._scene, false, false, Texture.NEAREST_SAMPLINGMODE);
    }

    /**
     * Gets the current list of ramp gradients.
     * You must use addRampGradient and removeRampGradient to udpate this list
     * @returns the list of ramp gradients
     */
    public getRampGradients(): Nullable<Array<Color3Gradient>> {
        return this._rampGradients;
    }

    /**
     * Adds a new ramp gradient used to remap particle colors
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param color defines the color to affect to the specified gradient
     * @returns the current particle system
     */
    public addRampGradient(gradient: number, color: Color3): ParticleSystem {
        if (!this._rampGradients) {
            this._rampGradients = [];
        }

        let rampGradient = new Color3Gradient();
        rampGradient.gradient = gradient;
        rampGradient.color = color;
        this._rampGradients.push(rampGradient);

        this._rampGradients.sort((a, b) => {
            if (a.gradient < b.gradient) {
                return -1;
            } else if (a.gradient > b.gradient) {
                return 1;
            }

            return 0;
        });

        if (this._rampGradientsTexture) {
            this._rampGradientsTexture.dispose();
            (<any>this._rampGradientsTexture) = null;
        }

        this._createRampGradientTexture();

        return this;
    }

    /**
     * Remove a specific ramp gradient
     * @param gradient defines the gradient to remove
     * @returns the current particle system
     */
    public removeRampGradient(gradient: number): ParticleSystem {
        this._removeGradientAndTexture(gradient, this._rampGradients, this._rampGradientsTexture);
        (<any>this._rampGradientsTexture) = null;

        if (this._rampGradients && this._rampGradients.length > 0) {
            this._createRampGradientTexture();
        }

        return this;
    }

    /**
     * Adds a new color gradient
     * @param gradient defines the gradient to use (between 0 and 1)
     * @param color1 defines the color to affect to the specified gradient
     * @param color2 defines an additional color used to define a range ([color, color2]) with main color to pick the final color from
     * @returns this particle system
     */
    public addColorGradient(gradient: number, color1: Color4, color2?: Color4): IParticleSystem {
        if (!this._colorGradients) {
            this._colorGradients = [];
        }

        let colorGradient = new ColorGradient();
        colorGradient.gradient = gradient;
        colorGradient.color1 = color1;
        colorGradient.color2 = color2;
        this._colorGradients.push(colorGradient);

        this._colorGradients.sort((a, b) => {
            if (a.gradient < b.gradient) {
                return -1;
            } else if (a.gradient > b.gradient) {
                return 1;
            }

            return 0;
        });

        return this;
    }

    /**
     * Remove a specific color gradient
     * @param gradient defines the gradient to remove
     * @returns this particle system
     */
    public removeColorGradient(gradient: number): IParticleSystem {
        if (!this._colorGradients) {
            return this;
        }

        let index = 0;
        for (var colorGradient of this._colorGradients) {
            if (colorGradient.gradient === gradient) {
                this._colorGradients.splice(index, 1);
                break;
            }
            index++;
        }

        return this;
    }

    private _fetchR(u: number, v: number, width: number, height: number, pixels: Uint8Array): number {
        u = Math.abs(u) * 0.5 + 0.5;
        v = Math.abs(v) * 0.5 + 0.5;

        let wrappedU = ((u * width) % width) | 0;
        let wrappedV = ((v * height) % height) | 0;

        let position = (wrappedU + wrappedV * width) * 4;
        return pixels[position] / 255;
    }

    protected _reset() {
        this._resetEffect();
    }

    private _resetEffect() {
        if (this._vertexBuffer) {
            this._vertexBuffer.dispose();
            this._vertexBuffer = null;
        }

        if (this._spriteBuffer) {
            this._spriteBuffer.dispose();
            this._spriteBuffer = null;
        }

        this._createVertexBuffers();
    }

    private _createVertexBuffers() {
        this._vertexBufferSize = this._useInstancing ? 10 : 12;
        if (this._isAnimationSheetEnabled) {
            this._vertexBufferSize += 1;
        }

        if (!this._isBillboardBased || this.billboardMode === ParticleSystem.BILLBOARDMODE_STRETCHED) {
            this._vertexBufferSize += 3;
        }

        if (this._useRampGradients) {
            this._vertexBufferSize += 4;
        }

        let engine = this._scene.getEngine();
        this._vertexData = new Float32Array(this._capacity * this._vertexBufferSize * (this._useInstancing ? 1 : 4));
        this._vertexBuffer = new Buffer(engine, this._vertexData, true, this._vertexBufferSize);

        let dataOffset = 0;
        var positions = this._vertexBuffer.createVertexBuffer(VertexBuffer.PositionKind, dataOffset, 3, this._vertexBufferSize, this._useInstancing);
        this._vertexBuffers[VertexBuffer.PositionKind] = positions;
        dataOffset += 3;

        var colors = this._vertexBuffer.createVertexBuffer(VertexBuffer.ColorKind, dataOffset, 4, this._vertexBufferSize, this._useInstancing);
        this._vertexBuffers[VertexBuffer.ColorKind] = colors;
        dataOffset += 4;

        var options = this._vertexBuffer.createVertexBuffer("angle", dataOffset, 1, this._vertexBufferSize, this._useInstancing);
        this._vertexBuffers["angle"] = options;
        dataOffset += 1;

        var size = this._vertexBuffer.createVertexBuffer("size", dataOffset, 2, this._vertexBufferSize, this._useInstancing);
        this._vertexBuffers["size"] = size;
        dataOffset += 2;

        if (this._isAnimationSheetEnabled) {
            var cellIndexBuffer = this._vertexBuffer.createVertexBuffer("cellIndex", dataOffset, 1, this._vertexBufferSize, this._useInstancing);
            this._vertexBuffers["cellIndex"] = cellIndexBuffer;
            dataOffset += 1;
        }

        if (!this._isBillboardBased || this.billboardMode === ParticleSystem.BILLBOARDMODE_STRETCHED) {
            var directionBuffer = this._vertexBuffer.createVertexBuffer("direction", dataOffset, 3, this._vertexBufferSize, this._useInstancing);
            this._vertexBuffers["direction"] = directionBuffer;
            dataOffset += 3;
        }

        if (this._useRampGradients) {
            var rampDataBuffer = this._vertexBuffer.createVertexBuffer("remapData", dataOffset, 4, this._vertexBufferSize, this._useInstancing);
            this._vertexBuffers["remapData"] = rampDataBuffer;
            dataOffset += 4;
        }

        var offsets: VertexBuffer;
        if (this._useInstancing) {
            var spriteData = new Float32Array([0, 0, 1, 0, 1, 1, 0, 1]);
            this._spriteBuffer = new Buffer(engine, spriteData, false, 2);
            offsets = this._spriteBuffer.createVertexBuffer("offset", 0, 2);
        } else {
            offsets = this._vertexBuffer.createVertexBuffer("offset", dataOffset, 2, this._vertexBufferSize, this._useInstancing);
            dataOffset += 2;
        }
        this._vertexBuffers["offset"] = offsets;

    }

    private _createIndexBuffer() {
        if (this._useInstancing) {
            return;
        }
        var indices = [];
        var index = 0;
        for (var count = 0; count < this._capacity; count++) {
            indices.push(index);
            indices.push(index + 1);
            indices.push(index + 2);
            indices.push(index);
            indices.push(index + 2);
            indices.push(index + 3);
            index += 4;
        }

        this._indexBuffer = this._scene.getEngine().createIndexBuffer(indices);
    }

    /**
     * Gets the maximum number of particles active at the same time.
     * @returns The max number of active particles.
     */
    public getCapacity(): number {
        return this._capacity;
    }

    /**
     * Gets whether there are still active particles in the system.
     * @returns True if it is alive, otherwise false.
     */
    public isAlive(): boolean {
        return this._alive;
    }

    /**
     * Gets if the system has been started. (Note: this will still be true after stop is called)
     * @returns True if it has been started, otherwise false.
     */
    public isStarted(): boolean {
        return this._started;
    }

    private _prepareSubEmitterInternalArray() {
        this._subEmitters = new Array<Array<SubEmitter>>();
        if (this.subEmitters) {
            this.subEmitters.forEach((subEmitter) => {
                if (subEmitter instanceof ParticleSystem) {
                    this._subEmitters.push([new SubEmitter(subEmitter)]);
                } else if (subEmitter instanceof SubEmitter) {
                    this._subEmitters.push([subEmitter]);
                } else if (subEmitter instanceof Array) {
                    this._subEmitters.push(subEmitter);
                }
            });
        }
    }

    /**
     * Starts the particle system and begins to emit
     * @param delay defines the delay in milliseconds before starting the system (this.startDelay by default)
     */
    public start(delay = this.startDelay): void {
        if (!this.targetStopDuration && this._hasTargetStopDurationDependantGradient()) {
            throw "Particle system started with a targetStopDuration dependant gradient (eg. startSizeGradients) but no targetStopDuration set";
        }
        if (delay) {
            setTimeout(() => {
                this.start(0);
            }, delay);
            return;
        }
        // Convert the subEmitters field to the constant type field _subEmitters
        this._prepareSubEmitterInternalArray();

        this._started = true;
        this._stopped = false;
        this._actualFrame = 0;
        if (this._subEmitters && this._subEmitters.length != 0) {
            this.activeSubSystems = new Array<ParticleSystem>();
        }

        // Reset emit gradient so it acts the same on every start
        if (this._emitRateGradients) {
            if (this._emitRateGradients.length > 0) {
                this._currentEmitRateGradient = this._emitRateGradients[0];
                this._currentEmitRate1 = this._currentEmitRateGradient.getFactor();
                this._currentEmitRate2 = this._currentEmitRate1;
            }
            if (this._emitRateGradients.length > 1) {
                this._currentEmitRate2 = this._emitRateGradients[1].getFactor();
            }
        }
        // Reset start size gradient so it acts the same on every start
        if (this._startSizeGradients) {
            if (this._startSizeGradients.length > 0) {
                this._currentStartSizeGradient = this._startSizeGradients[0];
                this._currentStartSize1 = this._currentStartSizeGradient.getFactor();
                this._currentStartSize2 = this._currentStartSize1;
            }
            if (this._startSizeGradients.length > 1) {
                this._currentStartSize2 = this._startSizeGradients[1].getFactor();
            }
        }

        if (this.preWarmCycles) {
            if (this.emitter instanceof AbstractMesh) {
                this.emitter.computeWorldMatrix(true);
            }

            let noiseTextureAsProcedural = this.noiseTexture as ProceduralTexture;

            if (noiseTextureAsProcedural && noiseTextureAsProcedural.onGeneratedObservable) {
                noiseTextureAsProcedural.onGeneratedObservable.addOnce(() => {
                    setTimeout(() => {
                        for (var index = 0; index < this.preWarmCycles; index++) {
                            this.animate(true);
                            noiseTextureAsProcedural.render();
                        }
                    });
                });
            } else {
                for (var index = 0; index < this.preWarmCycles; index++) {
                    this.animate(true);
                }
            }
        }

        // Animations
        if (this.beginAnimationOnStart && this.animations && this.animations.length > 0) {
            this.getScene().beginAnimation(this, this.beginAnimationFrom, this.beginAnimationTo, this.beginAnimationLoop);
        }
    }

    /**
     * Stops the particle system.
     * @param stopSubEmitters if true it will stop the current system and all created sub-Systems if false it will stop the current root system only, this param is used by the root particle system only. the default value is true.
     */
    public stop(stopSubEmitters = true): void {
        this._stopped = true;

        if (stopSubEmitters) {
            this._stopSubEmitters();
        }
    }

    // animation sheet

    /**
     * Remove all active particles
     */
    public reset(): void {
        this._stockParticles = [];
        this._particles = [];
    }

    /**
     * @hidden (for internal use only)
     */
    public _appendParticleVertex(index: number, particle: Particle, offsetX: number, offsetY: number): void {
        var offset = index * this._vertexBufferSize;

        this._vertexData[offset++] = particle.position.x + this.worldOffset.x;
        this._vertexData[offset++] = particle.position.y + this.worldOffset.y;
        this._vertexData[offset++] = particle.position.z + this.worldOffset.z;
        this._vertexData[offset++] = particle.color.r;
        this._vertexData[offset++] = particle.color.g;
        this._vertexData[offset++] = particle.color.b;
        this._vertexData[offset++] = particle.color.a;
        this._vertexData[offset++] = particle.angle;

        this._vertexData[offset++] = particle.scale.x * particle.size;
        this._vertexData[offset++] = particle.scale.y * particle.size;

        if (this._isAnimationSheetEnabled) {
            this._vertexData[offset++] = particle.cellIndex;
        }

        if (!this._isBillboardBased) {
            if (particle._initialDirection) {
                this._vertexData[offset++] = particle._initialDirection.x;
                this._vertexData[offset++] = particle._initialDirection.y;
                this._vertexData[offset++] = particle._initialDirection.z;
            } else {
                this._vertexData[offset++] = particle.direction.x;
                this._vertexData[offset++] = particle.direction.y;
                this._vertexData[offset++] = particle.direction.z;
            }
        } else if (this.billboardMode === ParticleSystem.BILLBOARDMODE_STRETCHED) {
            this._vertexData[offset++] = particle.direction.x;
            this._vertexData[offset++] = particle.direction.y;
            this._vertexData[offset++] = particle.direction.z;
        }

        if (this._useRampGradients) {
            this._vertexData[offset++] = particle.remapData.x;
            this._vertexData[offset++] = particle.remapData.y;
            this._vertexData[offset++] = particle.remapData.z;
            this._vertexData[offset++] = particle.remapData.w;
        }

        if (!this._useInstancing) {
            if (this._isAnimationSheetEnabled) {
                if (offsetX === 0) {
                    offsetX = this._epsilon;
                }
                else if (offsetX === 1) {
                    offsetX = 1 - this._epsilon;
                }

                if (offsetY === 0) {
                    offsetY = this._epsilon;
                }
                else if (offsetY === 1) {
                    offsetY = 1 - this._epsilon;
                }
            }

            this._vertexData[offset++] = offsetX;
            this._vertexData[offset++] = offsetY;
        }
    }

    // start of sub system methods

    /**
     * "Recycles" one of the particle by copying it back to the "stock" of particles and removing it from the active list.
     * Its lifetime will start back at 0.
     */
    public recycleParticle: (particle: Particle) => void = (particle) => {
        // move particle from activeParticle list to stock particles
        var lastParticle = <Particle>this._particles.pop();
        if (lastParticle !== particle) {
            lastParticle.copyTo(particle);
        }
        this._stockParticles.push(lastParticle);
    }

    private _stopSubEmitters(): void {
        if (!this.activeSubSystems) {
            return;
        }
        this.activeSubSystems.forEach((subSystem) => {
            subSystem.stop(true);
        });
        this.activeSubSystems = new Array<ParticleSystem>();
    }

    private _createParticle: () => Particle = () => {
        var particle: Particle;
        if (this._stockParticles.length !== 0) {
            particle = <Particle>this._stockParticles.pop();
            particle._reset();
        } else {
            particle = new Particle(this);
        }

        // Attach emitters
        if (this._subEmitters && this._subEmitters.length > 0) {
            var subEmitters = this._subEmitters[Math.floor(Math.random() * this._subEmitters.length)];
            particle._attachedSubEmitters = [];
            subEmitters.forEach((subEmitter) => {
                if (subEmitter.type === SubEmitterType.ATTACHED) {
                    var newEmitter = subEmitter.clone();
                    (<Array<SubEmitter>>particle._attachedSubEmitters).push(newEmitter);
                    newEmitter.particleSystem.start();
                }
            });
        }
        return particle;
    }

    private _removeFromRoot(): void {
        if (!this._rootParticleSystem) {
            return;
        }

        let index = this._rootParticleSystem.activeSubSystems.indexOf(this);
        if (index !== -1) {
            this._rootParticleSystem.activeSubSystems.splice(index, 1);
        }

        this._rootParticleSystem = null;
    }

    private _emitFromParticle: (particle: Particle) => void = (particle) => {
        if (!this._subEmitters || this._subEmitters.length === 0) {
            return;
        }
        var templateIndex = Math.floor(Math.random() * this._subEmitters.length);

        this._subEmitters[templateIndex].forEach((subEmitter) => {
            if (subEmitter.type === SubEmitterType.END) {
                var subSystem = subEmitter.clone();
                particle._inheritParticleInfoToSubEmitter(subSystem);
                subSystem.particleSystem._rootParticleSystem = this;
                this.activeSubSystems.push(subSystem.particleSystem);
                subSystem.particleSystem.start();
            }
        });
    }

    // End of sub system methods

    private _update(newParticles: number): void {
        // Update current
        this._alive = this._particles.length > 0;

        if ((<AbstractMesh>this.emitter).position) {
            var emitterMesh = (<AbstractMesh>this.emitter);
            this._emitterWorldMatrix = emitterMesh.getWorldMatrix();
        } else {
            var emitterPosition = (<Vector3>this.emitter);
            this._emitterWorldMatrix = Matrix.Translation(emitterPosition.x, emitterPosition.y, emitterPosition.z);
        }

        this.updateFunction(this._particles);

        // Add new ones
        var particle: Particle;
        for (var index = 0; index < newParticles; index++) {
            if (this._particles.length === this._capacity) {
                break;
            }

            particle = this._createParticle();

            this._particles.push(particle);

            // Emitter
            let emitPower = Scalar.RandomRange(this.minEmitPower, this.maxEmitPower);

            if (this.startPositionFunction) {
                this.startPositionFunction(this._emitterWorldMatrix, particle.position, particle);
            }
            else {
                this.particleEmitterType.startPositionFunction(this._emitterWorldMatrix, particle.position, particle);
            }

            if (this.startDirectionFunction) {
                this.startDirectionFunction(this._emitterWorldMatrix, particle.direction, particle);
            }
            else {
                this.particleEmitterType.startDirectionFunction(this._emitterWorldMatrix, particle.direction, particle);
            }

            if (emitPower === 0) {
                if (!particle._initialDirection) {
                    particle._initialDirection = particle.direction.clone();
                } else {
                    particle._initialDirection.copyFrom(particle.direction);
                }
            } else {
                particle._initialDirection = null;
            }

            particle.direction.scaleInPlace(emitPower);

            // Life time
            if (this.targetStopDuration && this._lifeTimeGradients && this._lifeTimeGradients.length > 0) {
                let ratio = Scalar.Clamp(this._actualFrame / this.targetStopDuration);
                GradientHelper.GetCurrentGradient(ratio, this._lifeTimeGradients, (currentGradient, nextGradient) => {
                    let factorGradient1 = (<FactorGradient>currentGradient);
                    let factorGradient2 = (<FactorGradient>nextGradient);
                    let lifeTime1 = factorGradient1.getFactor();
                    let lifeTime2 = factorGradient2.getFactor();
                    let gradient = (ratio - factorGradient1.gradient) / (factorGradient2.gradient - factorGradient1.gradient);
                    particle.lifeTime = Scalar.Lerp(lifeTime1, lifeTime2, gradient);
                });
            } else {
                particle.lifeTime = Scalar.RandomRange(this.minLifeTime, this.maxLifeTime);
            }

            // Size
            if (!this._sizeGradients || this._sizeGradients.length === 0) {
                particle.size = Scalar.RandomRange(this.minSize, this.maxSize);
            } else {
                particle._currentSizeGradient = this._sizeGradients[0];
                particle._currentSize1 = particle._currentSizeGradient.getFactor();
                particle.size = particle._currentSize1;

                if (this._sizeGradients.length > 1) {
                    particle._currentSize2 = this._sizeGradients[1].getFactor();
                } else {
                    particle._currentSize2 = particle._currentSize1;
                }
            }
            // Size and scale
            particle.scale.copyFromFloats(Scalar.RandomRange(this.minScaleX, this.maxScaleX), Scalar.RandomRange(this.minScaleY, this.maxScaleY));

            // Adjust scale by start size
            if (this._startSizeGradients && this._startSizeGradients[0] && this.targetStopDuration) {
                const ratio = this._actualFrame / this.targetStopDuration;
                GradientHelper.GetCurrentGradient(ratio, this._startSizeGradients, (currentGradient, nextGradient, scale) => {
                    if (currentGradient !== this._currentStartSizeGradient) {
                        this._currentStartSize1 = this._currentStartSize2;
                        this._currentStartSize2 = (<FactorGradient>nextGradient).getFactor();
                        this._currentStartSizeGradient = (<FactorGradient>currentGradient);
                    }

                    var value = Scalar.Lerp(this._currentStartSize1, this._currentStartSize2, scale);
                    particle.scale.scaleInPlace(value);
                });
            }

            // Angle
            if (!this._angularSpeedGradients || this._angularSpeedGradients.length === 0) {
                particle.angularSpeed = Scalar.RandomRange(this.minAngularSpeed, this.maxAngularSpeed);
            } else {
                particle._currentAngularSpeedGradient = this._angularSpeedGradients[0];
                particle.angularSpeed = particle._currentAngularSpeedGradient.getFactor();
                particle._currentAngularSpeed1 = particle.angularSpeed;

                if (this._angularSpeedGradients.length > 1) {
                    particle._currentAngularSpeed2 = this._angularSpeedGradients[1].getFactor();
                } else {
                    particle._currentAngularSpeed2 = particle._currentAngularSpeed1;
                }
            }
            particle.angle = Scalar.RandomRange(this.minInitialRotation, this.maxInitialRotation);

            // Velocity
            if (this._velocityGradients && this._velocityGradients.length > 0) {
                particle._currentVelocityGradient = this._velocityGradients[0];
                particle._currentVelocity1 = particle._currentVelocityGradient.getFactor();

                if (this._velocityGradients.length > 1) {
                    particle._currentVelocity2 = this._velocityGradients[1].getFactor();
                } else {
                    particle._currentVelocity2 = particle._currentVelocity1;
                }
            }

            // Limit velocity
            if (this._limitVelocityGradients && this._limitVelocityGradients.length > 0) {
                particle._currentLimitVelocityGradient = this._limitVelocityGradients[0];
                particle._currentLimitVelocity1 = particle._currentLimitVelocityGradient.getFactor();

                if (this._limitVelocityGradients.length > 1) {
                    particle._currentLimitVelocity2 = this._limitVelocityGradients[1].getFactor();
                } else {
                    particle._currentLimitVelocity2 = particle._currentLimitVelocity1;
                }
            }

            // Drag
            if (this._dragGradients && this._dragGradients.length > 0) {
                particle._currentDragGradient = this._dragGradients[0];
                particle._currentDrag1 = particle._currentDragGradient.getFactor();

                if (this._dragGradients.length > 1) {
                    particle._currentDrag2 = this._dragGradients[1].getFactor();
                } else {
                    particle._currentDrag2 = particle._currentDrag1;
                }
            }

            // Color
            if (!this._colorGradients || this._colorGradients.length === 0) {
                var step = Scalar.RandomRange(0, 1.0);

                Color4.LerpToRef(this.color1, this.color2, step, particle.color);

                this.colorDead.subtractToRef(particle.color, this._colorDiff);
                this._colorDiff.scaleToRef(1.0 / particle.lifeTime, particle.colorStep);
            } else {
                particle._currentColorGradient = this._colorGradients[0];
                particle._currentColorGradient.getColorToRef(particle.color);
                particle._currentColor1.copyFrom(particle.color);

                if (this._colorGradients.length > 1) {
                    this._colorGradients[1].getColorToRef(particle._currentColor2);
                } else {
                    particle._currentColor2.copyFrom(particle.color);
                }
            }

            // Sheet
            if (this._isAnimationSheetEnabled) {
                particle._initialStartSpriteCellID = this.startSpriteCellID;
                particle._initialEndSpriteCellID = this.endSpriteCellID;
            }

            // Inherited Velocity
            particle.direction.addInPlace(this._inheritedVelocityOffset);

            // Ramp
            if (this._useRampGradients) {
                particle.remapData = new Vector4(0, 1, 0, 1);
            }

            // Noise texture coordinates
            if (this.noiseTexture) {
                if (particle._randomNoiseCoordinates1) {
                    particle._randomNoiseCoordinates1.copyFromFloats(Math.random(), Math.random(), Math.random());
                    particle._randomNoiseCoordinates2.copyFromFloats(Math.random(), Math.random(), Math.random());
                } else {
                    particle._randomNoiseCoordinates1 = new Vector3(Math.random(), Math.random(), Math.random());
                    particle._randomNoiseCoordinates2 = new Vector3(Math.random(), Math.random(), Math.random());
                }
            }

            // Update the position of the attached sub-emitters to match their attached particle
            particle._inheritParticleInfoToSubEmitters();

        }
    }

    /** @hidden */
    public static _GetAttributeNamesOrOptions(isAnimationSheetEnabled = false, isBillboardBased = false, useRampGradients = false): string[] {
        var attributeNamesOrOptions = [VertexBuffer.PositionKind, VertexBuffer.ColorKind, "angle", "offset", "size"];

        if (isAnimationSheetEnabled) {
            attributeNamesOrOptions.push("cellIndex");
        }

        if (!isBillboardBased) {
            attributeNamesOrOptions.push("direction");
        }

        if (useRampGradients) {
            attributeNamesOrOptions.push("remapData");
        }

        return attributeNamesOrOptions;
    }

    /** @hidden */
    public static _GetEffectCreationOptions(isAnimationSheetEnabled = false): string[] {
        var effectCreationOption = ["invView", "view", "projection", "vClipPlane", "vClipPlane2", "vClipPlane3", "vClipPlane4", "textureMask", "translationPivot", "eyePosition"];

        if (isAnimationSheetEnabled) {
            effectCreationOption.push("particlesInfos");
        }

        return effectCreationOption;
    }

    /** @hidden */
    private _getEffect(blendMode: number): Effect {
        if (this._customEffect) {
            return this._customEffect;
        }

        var defines = [];

        if (this._scene.clipPlane) {
            defines.push("#define CLIPPLANE");
        }

        if (this._scene.clipPlane2) {
            defines.push("#define CLIPPLANE2");
        }

        if (this._scene.clipPlane3) {
            defines.push("#define CLIPPLANE3");
        }

        if (this._scene.clipPlane4) {
            defines.push("#define CLIPPLANE4");
        }

        if (this._isAnimationSheetEnabled) {
            defines.push("#define ANIMATESHEET");
        }

        if (blendMode === ParticleSystem.BLENDMODE_MULTIPLY) {
            defines.push("#define BLENDMULTIPLYMODE");
        }

        if (this._useRampGradients) {
            defines.push("#define RAMPGRADIENT");
        }

        if (this._isBillboardBased) {
            defines.push("#define BILLBOARD");

            switch (this.billboardMode) {
                case ParticleSystem.BILLBOARDMODE_Y:
                    defines.push("#define BILLBOARDY");
                    break;
                case ParticleSystem.BILLBOARDMODE_STRETCHED:
                    defines.push("#define BILLBOARDSTRETCHED");
                    break;
                case ParticleSystem.BILLBOARDMODE_ALL:
                default:
                    break;
            }
        }

        if (this._imageProcessingConfiguration) {
            this._imageProcessingConfiguration.prepareDefines(this._imageProcessingConfigurationDefines);
            defines.push(this._imageProcessingConfigurationDefines.toString());
        }

        // Effect
        var join = defines.join("\n");
        if (this._cachedDefines !== join) {
            this._cachedDefines = join;

            var attributesNamesOrOptions = ParticleSystem._GetAttributeNamesOrOptions(this._isAnimationSheetEnabled, this._isBillboardBased && this.billboardMode !== ParticleSystem.BILLBOARDMODE_STRETCHED, this._useRampGradients);
            var effectCreationOption = ParticleSystem._GetEffectCreationOptions(this._isAnimationSheetEnabled);

            var samplers = ["diffuseSampler", "rampSampler"];

            if (ImageProcessingConfiguration) {
                ImageProcessingConfiguration.PrepareUniforms(effectCreationOption, this._imageProcessingConfigurationDefines);
                ImageProcessingConfiguration.PrepareSamplers(samplers, this._imageProcessingConfigurationDefines);
            }

            this._effect = this._scene.getEngine().createEffect(
                "particles",
                attributesNamesOrOptions,
                effectCreationOption,
                samplers, join);
        }

        return this._effect;
    }

    /**
     * Animates the particle system for the current frame by emitting new particles and or animating the living ones.
     * @param preWarmOnly will prevent the system from updating the vertex buffer (default is false)
     */
    public animate(preWarmOnly = false): void {
        if (!this._started) {
            return;
        }

        if (!preWarmOnly) {
            // Check
            if (!this.isReady()) {
                return;
            }

            if (this._currentRenderId === this._scene.getFrameId()) {
                return;
            }
            this._currentRenderId = this._scene.getFrameId();
        }

        this._scaledUpdateSpeed = this.updateSpeed * (preWarmOnly ? this.preWarmStepOffset : this._scene.getAnimationRatio());

        // Determine the number of particles we need to create
        var newParticles;

        if (this.manualEmitCount > -1) {
            newParticles = this.manualEmitCount;
            this._newPartsExcess = 0;
            this.manualEmitCount = 0;
        } else {
            let rate = this.emitRate;

            if (this._emitRateGradients && this._emitRateGradients.length > 0 && this.targetStopDuration) {
                const ratio = this._actualFrame / this.targetStopDuration;
                GradientHelper.GetCurrentGradient(ratio, this._emitRateGradients, (currentGradient, nextGradient, scale) => {
                    if (currentGradient !== this._currentEmitRateGradient) {
                        this._currentEmitRate1 = this._currentEmitRate2;
                        this._currentEmitRate2 = (<FactorGradient>nextGradient).getFactor();
                        this._currentEmitRateGradient = (<FactorGradient>currentGradient);
                    }

                    rate = Scalar.Lerp(this._currentEmitRate1, this._currentEmitRate2, scale);
                });
            }

            newParticles = ((rate * this._scaledUpdateSpeed) >> 0);
            this._newPartsExcess += rate * this._scaledUpdateSpeed - newParticles;
        }

        if (this._newPartsExcess > 1.0) {
            newParticles += this._newPartsExcess >> 0;
            this._newPartsExcess -= this._newPartsExcess >> 0;
        }

        this._alive = false;

        if (!this._stopped) {
            this._actualFrame += this._scaledUpdateSpeed;

            if (this.targetStopDuration && this._actualFrame >= this.targetStopDuration) {
                this.stop();
            }
        } else {
            newParticles = 0;
        }
        this._update(newParticles);

        // Stopped?
        if (this._stopped) {
            if (!this._alive) {
                this._started = false;
                if (this.onAnimationEnd) {
                    this.onAnimationEnd();
                }
                if (this.disposeOnStop) {
                    this._scene._toBeDisposed.push(this);
                }
            }
        }

        if (!preWarmOnly) {
            // Update VBO
            var offset = 0;
            for (var index = 0; index < this._particles.length; index++) {
                var particle = this._particles[index];
                this._appendParticleVertices(offset, particle);
                offset += this._useInstancing ? 1 : 4;
            }

            if (this._vertexBuffer) {
                this._vertexBuffer.update(this._vertexData);
            }
        }

        if (this.manualEmitCount === 0 && this.disposeOnStop) {
            this.stop();
        }
    }

    private _appendParticleVertices(offset: number, particle: Particle) {
        this._appendParticleVertex(offset++, particle, 0, 0);
        if (!this._useInstancing) {
            this._appendParticleVertex(offset++, particle, 1, 0);
            this._appendParticleVertex(offset++, particle, 1, 1);
            this._appendParticleVertex(offset++, particle, 0, 1);
        }
    }

    /**
     * Rebuilds the particle system.
     */
    public rebuild(): void {
        this._createIndexBuffer();

        if (this._vertexBuffer) {
            this._vertexBuffer._rebuild();
        }

        for (var key in this._vertexBuffers) {
            this._vertexBuffers[key]._rebuild();
        }
    }

    /**
     * Is this system ready to be used/rendered
     * @return true if the system is ready
     */
    public isReady(): boolean {
        if (!this.emitter || !this._imageProcessingConfiguration.isReady() || !this.particleTexture || !this.particleTexture.isReady()) {
            return false;
        }

        if (this.blendMode !== ParticleSystem.BLENDMODE_MULTIPLYADD) {
            if (!this._getEffect(this.blendMode).isReady()) {
                return false;
            }
        } else {
            if (!this._getEffect(ParticleSystem.BLENDMODE_MULTIPLY).isReady()) {
                return false;
            }
            if (!this._getEffect(ParticleSystem.BLENDMODE_ADD).isReady()) {
                return false;
            }
        }

        return true;
    }

    private _render(blendMode: number) {
        var effect = this._getEffect(blendMode);

        var engine = this._scene.getEngine();

        // Render
        engine.enableEffect(effect);

        var viewMatrix = this._scene.getViewMatrix();
        effect.setTexture("diffuseSampler", this.particleTexture);
        effect.setMatrix("view", viewMatrix);
        effect.setMatrix("projection", this._scene.getProjectionMatrix());

        if (this._isAnimationSheetEnabled && this.particleTexture) {
            var baseSize = this.particleTexture.getBaseSize();
            effect.setFloat3("particlesInfos", this.spriteCellWidth / baseSize.width, this.spriteCellHeight / baseSize.height, baseSize.width / this.spriteCellWidth);
        }

        effect.setVector2("translationPivot", this.translationPivot);
        effect.setFloat4("textureMask", this.textureMask.r, this.textureMask.g, this.textureMask.b, this.textureMask.a);

        if (this._isBillboardBased) {
            var camera = this._scene.activeCamera!;
            effect.setVector3("eyePosition", camera.globalPosition);
        }

        if (this._rampGradientsTexture) {
            effect.setTexture("rampSampler", this._rampGradientsTexture);
        }

        if (this._scene.clipPlane || this._scene.clipPlane2 || this._scene.clipPlane3 || this._scene.clipPlane4) {
            var invView = viewMatrix.clone();
            invView.invert();
            effect.setMatrix("invView", invView);
            MaterialHelper.BindClipPlane(effect, this._scene);
        }

        engine.bindBuffers(this._vertexBuffers, this._indexBuffer, effect);

        // image processing
        if (this._imageProcessingConfiguration && !this._imageProcessingConfiguration.applyByPostProcess) {
            this._imageProcessingConfiguration.bind(effect);
        }

        // Draw order
        switch (blendMode) {
            case ParticleSystem.BLENDMODE_ADD:
                engine.setAlphaMode(Constants.ALPHA_ADD);
                break;
            case ParticleSystem.BLENDMODE_ONEONE:
                engine.setAlphaMode(Constants.ALPHA_ONEONE);
                break;
            case ParticleSystem.BLENDMODE_STANDARD:
                engine.setAlphaMode(Constants.ALPHA_COMBINE);
                break;
            case ParticleSystem.BLENDMODE_MULTIPLY:
                engine.setAlphaMode(Constants.ALPHA_MULTIPLY);
                break;
        }

        if (this._useInstancing) {
            engine.drawArraysType(Material.TriangleFanDrawMode, 0, 4, this._particles.length);
        } else {
            engine.drawElementsType(Material.TriangleFillMode, 0, this._particles.length * 6);
        }

        return this._particles.length;
    }

    /**
     * Renders the particle system in its current state.
     * @returns the current number of particles
     */
    public render(): number {
        // Check
        if (!this.isReady() || !this._particles.length) {
            return 0;
        }

        var engine = this._scene.getEngine();
        engine.setState(false);

        if (this.forceDepthWrite) {
            engine.setDepthWrite(true);
        }

        let outparticles = 0;

        if (this.blendMode === ParticleSystem.BLENDMODE_MULTIPLYADD) {
            outparticles = this._render(ParticleSystem.BLENDMODE_MULTIPLY) + this._render(ParticleSystem.BLENDMODE_ADD);
        }
        outparticles = this._render(this.blendMode);

        engine.unbindInstanceAttributes();
        engine.setAlphaMode(Constants.ALPHA_DISABLE);

        return outparticles;
    }

    /**
     * Disposes the particle system and free the associated resources
     * @param disposeTexture defines if the particule texture must be disposed as well (true by default)
     */
    public dispose(disposeTexture = true): void {
        if (this._vertexBuffer) {
            this._vertexBuffer.dispose();
            this._vertexBuffer = null;
        }

        if (this._spriteBuffer) {
            this._spriteBuffer.dispose();
            this._spriteBuffer = null;
        }

        if (this._indexBuffer) {
            this._scene.getEngine()._releaseBuffer(this._indexBuffer);
            this._indexBuffer = null;
        }

        if (disposeTexture && this.particleTexture) {
            this.particleTexture.dispose();
            this.particleTexture = null;
        }

        if (disposeTexture && this.noiseTexture) {
            this.noiseTexture.dispose();
            this.noiseTexture = null;
        }

        if (this._rampGradientsTexture) {
            this._rampGradientsTexture.dispose();
            this._rampGradientsTexture = null;
        }

        this._removeFromRoot();

        if (this._subEmitters && this._subEmitters.length) {
            for (var index = 0; index < this._subEmitters.length; index++) {
                for (var subEmitter of this._subEmitters[index]) {
                    subEmitter.dispose();
                }
            }

            this._subEmitters = [];
            this.subEmitters = [];
        }

        if (this._disposeEmitterOnDispose && this.emitter && (this.emitter as AbstractMesh).dispose) {
            (<AbstractMesh>this.emitter).dispose(true);
        }

        // Remove from scene
        var index = this._scene.particleSystems.indexOf(this);
        if (index > -1) {
            this._scene.particleSystems.splice(index, 1);
        }

        this._scene._activeParticleSystems.dispose();

        // Callback
        this.onDisposeObservable.notifyObservers(this);
        this.onDisposeObservable.clear();

        this.reset();
    }

    // Clone
    /**
     * Clones the particle system.
     * @param name The name of the cloned object
     * @param newEmitter The new emitter to use
     * @returns the cloned particle system
     */
    public clone(name: string, newEmitter: any): ParticleSystem {
        var custom: Nullable<Effect> = null;
        var program: any = null;
        if (this.customShader != null) {
            program = this.customShader;
            var defines: string = (program.shaderOptions.defines.length > 0) ? program.shaderOptions.defines.join("\n") : "";
            custom = this._scene.getEngine().createEffectForParticles(program.shaderPath.fragmentElement, program.shaderOptions.uniforms, program.shaderOptions.samplers, defines);
        } else if (this._customEffect) {
            custom = this._customEffect;
        }
        var result = new ParticleSystem(name, this._capacity, this._scene, custom);
        result.customShader = program;

        DeepCopier.DeepCopy(this, result, ["particles", "customShader", "noiseTexture", "particleTexture", "onDisposeObservable"]);

        if (newEmitter === undefined) {
            newEmitter = this.emitter;
        }

        result.noiseTexture = this.noiseTexture;
        result.emitter = newEmitter;
        if (this.particleTexture) {
            result.particleTexture = new Texture(this.particleTexture.url, this._scene);
        }

        // Clone gradients
        if (this._colorGradients) {
            this._colorGradients.forEach((v) => {
                result.addColorGradient(v.gradient, v.color1, v.color2);
            });
        }
        if (this._dragGradients) {
            this._dragGradients.forEach((v) => {
                result.addDragGradient(v.gradient, v.factor1, v.factor2);
            });
        }
        if (this._angularSpeedGradients) {
            this._angularSpeedGradients.forEach((v) => {
                result.addAngularSpeedGradient(v.gradient, v.factor1, v.factor2);
            });
        }
        if (this._emitRateGradients) {
            this._emitRateGradients.forEach((v) => {
                result.addEmitRateGradient(v.gradient, v.factor1, v.factor2);
            });
        }
        if (this._lifeTimeGradients) {
            this._lifeTimeGradients.forEach((v) => {
                result.addLifeTimeGradient(v.gradient, v.factor1, v.factor2);
            });
        }
        if (this._limitVelocityGradients) {
            this._limitVelocityGradients.forEach((v) => {
                result.addLimitVelocityGradient(v.gradient, v.factor1, v.factor2);
            });
        }
        if (this._sizeGradients) {
            this._sizeGradients.forEach((v) => {
                result.addSizeGradient(v.gradient, v.factor1, v.factor2);
            });
        }
        if (this._startSizeGradients) {
            this._startSizeGradients.forEach((v) => {
                result.addStartSizeGradient(v.gradient, v.factor1, v.factor2);
            });
        }
        if (this._velocityGradients) {
            this._velocityGradients.forEach((v) => {
                result.addVelocityGradient(v.gradient, v.factor1, v.factor2);
            });
        }
        if (this._rampGradients) {
            this._rampGradients.forEach((v) => {
                result.addRampGradient(v.gradient, v.color);
            });
        }
        if (this._colorRemapGradients) {
            this._colorRemapGradients.forEach((v) => {
                result.addColorRemapGradient(v.gradient, v.factor1, v.factor2!);
            });
        }
        if (this._alphaRemapGradients) {
            this._alphaRemapGradients.forEach((v) => {
                result.addAlphaRemapGradient(v.gradient, v.factor1, v.factor2!);
            });
        }

        if (!this.preventAutoStart) {
            result.start();
        }

        return result;
    }

    /**
     * Serializes the particle system to a JSON object.
     * @returns the JSON object
     */
    public serialize(): any {
        var serializationObject: any = {};

        ParticleSystem._Serialize(serializationObject, this);

        serializationObject.textureMask = this.textureMask.asArray();
        serializationObject.customShader = this.customShader;
        serializationObject.preventAutoStart = this.preventAutoStart;

        // SubEmitters
        if (this.subEmitters) {
            serializationObject.subEmitters = [];

            if (!this._subEmitters) {
                this._prepareSubEmitterInternalArray();
            }

            for (var subs of this._subEmitters) {
                let cell = [];
                for (var sub of subs) {
                    cell.push(sub.serialize());
                }

                serializationObject.subEmitters.push(cell);
            }
        }

        return serializationObject;
    }

    /** @hidden */
    public static _Serialize(serializationObject: any, particleSystem: IParticleSystem) {
        serializationObject.name = particleSystem.name;
        serializationObject.id = particleSystem.id;

        serializationObject.capacity = particleSystem.getCapacity();

        // Emitter
        if ((<AbstractMesh>particleSystem.emitter).position) {
            var emitterMesh = (<AbstractMesh>particleSystem.emitter);
            serializationObject.emitterId = emitterMesh.id;
        } else {
            var emitterPosition = (<Vector3>particleSystem.emitter);
            serializationObject.emitter = emitterPosition.asArray();
        }

        // Emitter
        if (particleSystem.particleEmitterType) {
            serializationObject.particleEmitterType = particleSystem.particleEmitterType.serialize();
        }

        if (particleSystem.particleTexture) {
            serializationObject.textureName = particleSystem.particleTexture.name;
            serializationObject.invertY = particleSystem.particleTexture._invertY;
        }

        // Animations
        SerializationHelper.AppendSerializedAnimations(particleSystem, serializationObject);
        serializationObject.beginAnimationOnStart = particleSystem.beginAnimationOnStart;
        serializationObject.beginAnimationFrom = particleSystem.beginAnimationFrom;
        serializationObject.beginAnimationTo = particleSystem.beginAnimationTo;
        serializationObject.beginAnimationLoop = particleSystem.beginAnimationLoop;

        // Particle system
        serializationObject.startDelay = particleSystem.startDelay;
        serializationObject.renderingGroupId = particleSystem.renderingGroupId;
        serializationObject.isBillboardBased = particleSystem.isBillboardBased;
        serializationObject.billboardMode = particleSystem.billboardMode;
        serializationObject.minAngularSpeed = particleSystem.minAngularSpeed;
        serializationObject.maxAngularSpeed = particleSystem.maxAngularSpeed;
        serializationObject.minSize = particleSystem.minSize;
        serializationObject.maxSize = particleSystem.maxSize;
        serializationObject.minScaleX = particleSystem.minScaleX;
        serializationObject.maxScaleX = particleSystem.maxScaleX;
        serializationObject.minScaleY = particleSystem.minScaleY;
        serializationObject.maxScaleY = particleSystem.maxScaleY;
        serializationObject.minEmitPower = particleSystem.minEmitPower;
        serializationObject.maxEmitPower = particleSystem.maxEmitPower;
        serializationObject.minLifeTime = particleSystem.minLifeTime;
        serializationObject.maxLifeTime = particleSystem.maxLifeTime;
        serializationObject.emitRate = particleSystem.emitRate;
        serializationObject.gravity = particleSystem.gravity.asArray();
        serializationObject.noiseStrength = particleSystem.noiseStrength.asArray();
        serializationObject.color1 = particleSystem.color1.asArray();
        serializationObject.color2 = particleSystem.color2.asArray();
        serializationObject.colorDead = particleSystem.colorDead.asArray();
        serializationObject.updateSpeed = particleSystem.updateSpeed;
        serializationObject.targetStopDuration = particleSystem.targetStopDuration;
        serializationObject.blendMode = particleSystem.blendMode;
        serializationObject.preWarmCycles = particleSystem.preWarmCycles;
        serializationObject.preWarmStepOffset = particleSystem.preWarmStepOffset;
        serializationObject.minInitialRotation = particleSystem.minInitialRotation;
        serializationObject.maxInitialRotation = particleSystem.maxInitialRotation;
        serializationObject.startSpriteCellID = particleSystem.startSpriteCellID;
        serializationObject.endSpriteCellID = particleSystem.endSpriteCellID;
        serializationObject.spriteCellChangeSpeed = particleSystem.spriteCellChangeSpeed;
        serializationObject.spriteCellWidth = particleSystem.spriteCellWidth;
        serializationObject.spriteCellHeight = particleSystem.spriteCellHeight;
        serializationObject.spriteRandomStartCell = particleSystem.spriteRandomStartCell;
        serializationObject.isAnimationSheetEnabled = particleSystem.isAnimationSheetEnabled;

        let colorGradients = particleSystem.getColorGradients();
        if (colorGradients) {
            serializationObject.colorGradients = [];
            for (var colorGradient of colorGradients) {
                var serializedGradient: any = {
                    gradient: colorGradient.gradient,
                    color1: colorGradient.color1.asArray()
                };

                if (colorGradient.color2) {
                    serializedGradient.color2 = colorGradient.color2.asArray();
                }

                serializationObject.colorGradients.push(serializedGradient);
            }
        }

        let rampGradients = particleSystem.getRampGradients();
        if (rampGradients) {
            serializationObject.rampGradients = [];
            for (var rampGradient of rampGradients) {
                var serializedGradient: any = {
                    gradient: rampGradient.gradient,
                    color: rampGradient.color.asArray()
                };

                serializationObject.rampGradients.push(serializedGradient);
            }
            serializationObject.useRampGradients = particleSystem.useRampGradients;
        }

        let colorRemapGradients = particleSystem.getColorRemapGradients();
        if (colorRemapGradients) {
            serializationObject.colorRemapGradients = [];
            for (var colorRemapGradient of colorRemapGradients) {

                var serializedGradient: any = {
                    gradient: colorRemapGradient.gradient,
                    factor1: colorRemapGradient.factor1
                };

                if (colorRemapGradient.factor2 !== undefined) {
                    serializedGradient.factor2 = colorRemapGradient.factor2;
                }

                serializationObject.colorRemapGradients.push(serializedGradient);
            }
        }

        let alphaRemapGradients = particleSystem.getAlphaRemapGradients();
        if (alphaRemapGradients) {
            serializationObject.alphaRemapGradients = [];
            for (var alphaRemapGradient of alphaRemapGradients) {

                var serializedGradient: any = {
                    gradient: alphaRemapGradient.gradient,
                    factor1: alphaRemapGradient.factor1
                };

                if (alphaRemapGradient.factor2 !== undefined) {
                    serializedGradient.factor2 = alphaRemapGradient.factor2;
                }

                serializationObject.alphaRemapGradients.push(serializedGradient);
            }
        }

        let sizeGradients = particleSystem.getSizeGradients();
        if (sizeGradients) {
            serializationObject.sizeGradients = [];
            for (var sizeGradient of sizeGradients) {

                var serializedGradient: any = {
                    gradient: sizeGradient.gradient,
                    factor1: sizeGradient.factor1
                };

                if (sizeGradient.factor2 !== undefined) {
                    serializedGradient.factor2 = sizeGradient.factor2;
                }

                serializationObject.sizeGradients.push(serializedGradient);
            }
        }

        let angularSpeedGradients = particleSystem.getAngularSpeedGradients();
        if (angularSpeedGradients) {
            serializationObject.angularSpeedGradients = [];
            for (var angularSpeedGradient of angularSpeedGradients) {

                var serializedGradient: any = {
                    gradient: angularSpeedGradient.gradient,
                    factor1: angularSpeedGradient.factor1
                };

                if (angularSpeedGradient.factor2 !== undefined) {
                    serializedGradient.factor2 = angularSpeedGradient.factor2;
                }

                serializationObject.angularSpeedGradients.push(serializedGradient);
            }
        }

        let velocityGradients = particleSystem.getVelocityGradients();
        if (velocityGradients) {
            serializationObject.velocityGradients = [];
            for (var velocityGradient of velocityGradients) {

                var serializedGradient: any = {
                    gradient: velocityGradient.gradient,
                    factor1: velocityGradient.factor1
                };

                if (velocityGradient.factor2 !== undefined) {
                    serializedGradient.factor2 = velocityGradient.factor2;
                }

                serializationObject.velocityGradients.push(serializedGradient);
            }
        }

        let dragGradients = particleSystem.getDragGradients();
        if (dragGradients) {
            serializationObject.dragGradients = [];
            for (var dragGradient of dragGradients) {

                var serializedGradient: any = {
                    gradient: dragGradient.gradient,
                    factor1: dragGradient.factor1
                };

                if (dragGradient.factor2 !== undefined) {
                    serializedGradient.factor2 = dragGradient.factor2;
                }

                serializationObject.dragGradients.push(serializedGradient);
            }
        }

        let emitRateGradients = particleSystem.getEmitRateGradients();
        if (emitRateGradients) {
            serializationObject.emitRateGradients = [];
            for (var emitRateGradient of emitRateGradients) {

                var serializedGradient: any = {
                    gradient: emitRateGradient.gradient,
                    factor1: emitRateGradient.factor1
                };

                if (emitRateGradient.factor2 !== undefined) {
                    serializedGradient.factor2 = emitRateGradient.factor2;
                }

                serializationObject.emitRateGradients.push(serializedGradient);
            }
        }

        let startSizeGradients = particleSystem.getStartSizeGradients();
        if (startSizeGradients) {
            serializationObject.startSizeGradients = [];
            for (var startSizeGradient of startSizeGradients) {

                var serializedGradient: any = {
                    gradient: startSizeGradient.gradient,
                    factor1: startSizeGradient.factor1
                };

                if (startSizeGradient.factor2 !== undefined) {
                    serializedGradient.factor2 = startSizeGradient.factor2;
                }

                serializationObject.startSizeGradients.push(serializedGradient);
            }
        }

        let lifeTimeGradients = particleSystem.getLifeTimeGradients();
        if (lifeTimeGradients) {
            serializationObject.lifeTimeGradients = [];
            for (var lifeTimeGradient of lifeTimeGradients) {

                var serializedGradient: any = {
                    gradient: lifeTimeGradient.gradient,
                    factor1: lifeTimeGradient.factor1
                };

                if (lifeTimeGradient.factor2 !== undefined) {
                    serializedGradient.factor2 = lifeTimeGradient.factor2;
                }

                serializationObject.lifeTimeGradients.push(serializedGradient);
            }
        }

        let limitVelocityGradients = particleSystem.getLimitVelocityGradients();
        if (limitVelocityGradients) {
            serializationObject.limitVelocityGradients = [];
            for (var limitVelocityGradient of limitVelocityGradients) {

                var serializedGradient: any = {
                    gradient: limitVelocityGradient.gradient,
                    factor1: limitVelocityGradient.factor1
                };

                if (limitVelocityGradient.factor2 !== undefined) {
                    serializedGradient.factor2 = limitVelocityGradient.factor2;
                }

                serializationObject.limitVelocityGradients.push(serializedGradient);
            }

            serializationObject.limitVelocityDamping = particleSystem.limitVelocityDamping;
        }

        if (particleSystem.noiseTexture) {
            serializationObject.noiseTexture = particleSystem.noiseTexture.serialize();
        }
    }

    /** @hidden */
    public static _Parse(parsedParticleSystem: any, particleSystem: IParticleSystem, scene: Scene, rootUrl: string) {
        // Texture
        if (parsedParticleSystem.textureName) {
            particleSystem.particleTexture = new Texture(rootUrl + parsedParticleSystem.textureName, scene, false, parsedParticleSystem.invertY !== undefined ? parsedParticleSystem.invertY : true);
            particleSystem.particleTexture.name = parsedParticleSystem.textureName;
        }

        // Emitter
        if (!parsedParticleSystem.emitterId && parsedParticleSystem.emitterId !== 0 && parsedParticleSystem.emitter === undefined) {
            particleSystem.emitter = Vector3.Zero();
        }
        else if (parsedParticleSystem.emitterId) {
            particleSystem.emitter = scene.getLastMeshByID(parsedParticleSystem.emitterId);
        } else {
            particleSystem.emitter = Vector3.FromArray(parsedParticleSystem.emitter);
        }

        // Misc.
        if (parsedParticleSystem.renderingGroupId !== undefined) {
            particleSystem.renderingGroupId = parsedParticleSystem.renderingGroupId;
        }

        if (parsedParticleSystem.isBillboardBased !== undefined) {
            particleSystem.isBillboardBased = parsedParticleSystem.isBillboardBased;
        }

        if (parsedParticleSystem.billboardMode !== undefined) {
            particleSystem.billboardMode = parsedParticleSystem.billboardMode;
        }

        // Animations
        if (parsedParticleSystem.animations) {
            for (var animationIndex = 0; animationIndex < parsedParticleSystem.animations.length; animationIndex++) {
                var parsedAnimation = parsedParticleSystem.animations[animationIndex];
                const internalClass = _TypeStore.GetClass("BABYLON.Animation");
                if (internalClass) {
                    particleSystem.animations.push(internalClass.Parse(parsedAnimation));
                }
            }
            particleSystem.beginAnimationOnStart = parsedParticleSystem.beginAnimationOnStart;
            particleSystem.beginAnimationFrom = parsedParticleSystem.beginAnimationFrom;
            particleSystem.beginAnimationTo = parsedParticleSystem.beginAnimationTo;
            particleSystem.beginAnimationLoop = parsedParticleSystem.beginAnimationLoop;
        }

        if (parsedParticleSystem.autoAnimate) {
            scene.beginAnimation(particleSystem, parsedParticleSystem.autoAnimateFrom, parsedParticleSystem.autoAnimateTo, parsedParticleSystem.autoAnimateLoop, parsedParticleSystem.autoAnimateSpeed || 1.0);
        }

        // Particle system
        particleSystem.startDelay = parsedParticleSystem.startDelay | 0;
        particleSystem.minAngularSpeed = parsedParticleSystem.minAngularSpeed;
        particleSystem.maxAngularSpeed = parsedParticleSystem.maxAngularSpeed;
        particleSystem.minSize = parsedParticleSystem.minSize;
        particleSystem.maxSize = parsedParticleSystem.maxSize;

        if (parsedParticleSystem.minScaleX) {
            particleSystem.minScaleX = parsedParticleSystem.minScaleX;
            particleSystem.maxScaleX = parsedParticleSystem.maxScaleX;
            particleSystem.minScaleY = parsedParticleSystem.minScaleY;
            particleSystem.maxScaleY = parsedParticleSystem.maxScaleY;
        }

        if (parsedParticleSystem.preWarmCycles !== undefined) {
            particleSystem.preWarmCycles = parsedParticleSystem.preWarmCycles;
            particleSystem.preWarmStepOffset = parsedParticleSystem.preWarmStepOffset;
        }

        if (parsedParticleSystem.minInitialRotation !== undefined) {
            particleSystem.minInitialRotation = parsedParticleSystem.minInitialRotation;
            particleSystem.maxInitialRotation = parsedParticleSystem.maxInitialRotation;
        }

        particleSystem.minLifeTime = parsedParticleSystem.minLifeTime;
        particleSystem.maxLifeTime = parsedParticleSystem.maxLifeTime;
        particleSystem.minEmitPower = parsedParticleSystem.minEmitPower;
        particleSystem.maxEmitPower = parsedParticleSystem.maxEmitPower;
        particleSystem.emitRate = parsedParticleSystem.emitRate;
        particleSystem.gravity = Vector3.FromArray(parsedParticleSystem.gravity);
        if (parsedParticleSystem.noiseStrength) {
            particleSystem.noiseStrength = Vector3.FromArray(parsedParticleSystem.noiseStrength);
        }
        particleSystem.color1 = Color4.FromArray(parsedParticleSystem.color1);
        particleSystem.color2 = Color4.FromArray(parsedParticleSystem.color2);
        particleSystem.colorDead = Color4.FromArray(parsedParticleSystem.colorDead);
        particleSystem.updateSpeed = parsedParticleSystem.updateSpeed;
        particleSystem.targetStopDuration = parsedParticleSystem.targetStopDuration;
        particleSystem.blendMode = parsedParticleSystem.blendMode;

        if (parsedParticleSystem.colorGradients) {
            for (var colorGradient of parsedParticleSystem.colorGradients) {
                particleSystem.addColorGradient(colorGradient.gradient, Color4.FromArray(colorGradient.color1), colorGradient.color2 ? Color4.FromArray(colorGradient.color2) : undefined);
            }
        }

        if (parsedParticleSystem.rampGradients) {
            for (var rampGradient of parsedParticleSystem.rampGradients) {
                particleSystem.addRampGradient(rampGradient.gradient, Color3.FromArray(rampGradient.color));
            }
            particleSystem.useRampGradients = parsedParticleSystem.useRampGradients;
        }

        if (parsedParticleSystem.colorRemapGradients) {
            for (var colorRemapGradient of parsedParticleSystem.colorRemapGradients) {
                particleSystem.addColorRemapGradient(colorRemapGradient.gradient, colorRemapGradient.factor1 !== undefined ? colorRemapGradient.factor1 : colorRemapGradient.factor, colorRemapGradient.factor2);
            }
        }

        if (parsedParticleSystem.alphaRemapGradients) {
            for (var alphaRemapGradient of parsedParticleSystem.alphaRemapGradients) {
                particleSystem.addAlphaRemapGradient(alphaRemapGradient.gradient, alphaRemapGradient.factor1 !== undefined ? alphaRemapGradient.factor1 : alphaRemapGradient.factor, alphaRemapGradient.factor2);
            }
        }

        if (parsedParticleSystem.sizeGradients) {
            for (var sizeGradient of parsedParticleSystem.sizeGradients) {
                particleSystem.addSizeGradient(sizeGradient.gradient, sizeGradient.factor1 !== undefined ? sizeGradient.factor1 : sizeGradient.factor, sizeGradient.factor2);
            }
        }

        if (parsedParticleSystem.angularSpeedGradients) {
            for (var angularSpeedGradient of parsedParticleSystem.angularSpeedGradients) {
                particleSystem.addAngularSpeedGradient(angularSpeedGradient.gradient, angularSpeedGradient.factor1 !== undefined ? angularSpeedGradient.factor1 : angularSpeedGradient.factor, angularSpeedGradient.factor2);
            }
        }

        if (parsedParticleSystem.velocityGradients) {
            for (var velocityGradient of parsedParticleSystem.velocityGradients) {
                particleSystem.addVelocityGradient(velocityGradient.gradient, velocityGradient.factor1 !== undefined ? velocityGradient.factor1 : velocityGradient.factor, velocityGradient.factor2);
            }
        }

        if (parsedParticleSystem.dragGradients) {
            for (var dragGradient of parsedParticleSystem.dragGradients) {
                particleSystem.addDragGradient(dragGradient.gradient, dragGradient.factor1 !== undefined ? dragGradient.factor1 : dragGradient.factor, dragGradient.factor2);
            }
        }

        if (parsedParticleSystem.emitRateGradients) {
            for (var emitRateGradient of parsedParticleSystem.emitRateGradients) {
                particleSystem.addEmitRateGradient(emitRateGradient.gradient, emitRateGradient.factor1 !== undefined ? emitRateGradient.factor1 : emitRateGradient.factor, emitRateGradient.factor2);
            }
        }

        if (parsedParticleSystem.startSizeGradients) {
            for (var startSizeGradient of parsedParticleSystem.startSizeGradients) {
                particleSystem.addStartSizeGradient(startSizeGradient.gradient, startSizeGradient.factor1 !== undefined ? startSizeGradient.factor1 : startSizeGradient.factor, startSizeGradient.factor2);
            }
        }

        if (parsedParticleSystem.lifeTimeGradients) {
            for (var lifeTimeGradient of parsedParticleSystem.lifeTimeGradients) {
                particleSystem.addLifeTimeGradient(lifeTimeGradient.gradient, lifeTimeGradient.factor1 !== undefined ? lifeTimeGradient.factor1 : lifeTimeGradient.factor, lifeTimeGradient.factor2);
            }
        }

        if (parsedParticleSystem.limitVelocityGradients) {
            for (var limitVelocityGradient of parsedParticleSystem.limitVelocityGradients) {
                particleSystem.addLimitVelocityGradient(limitVelocityGradient.gradient, limitVelocityGradient.factor1 !== undefined ? limitVelocityGradient.factor1 : limitVelocityGradient.factor, limitVelocityGradient.factor2);
            }
            particleSystem.limitVelocityDamping = parsedParticleSystem.limitVelocityDamping;
        }

        if (parsedParticleSystem.noiseTexture) {
            particleSystem.noiseTexture = ProceduralTexture.Parse(parsedParticleSystem.noiseTexture, scene, rootUrl);
        }

        // Emitter
        let emitterType: IParticleEmitterType;
        if (parsedParticleSystem.particleEmitterType) {
            switch (parsedParticleSystem.particleEmitterType.type) {
                case "SphereParticleEmitter":
                    emitterType = new SphereParticleEmitter();
                    break;
                case "SphereDirectedParticleEmitter":
                    emitterType = new SphereDirectedParticleEmitter();
                    break;
                case "ConeEmitter":
                case "ConeParticleEmitter":
                    emitterType = new ConeParticleEmitter();
                    break;
                case "CylinderParticleEmitter":
                    emitterType = new CylinderParticleEmitter();
                    break;
                case "HemisphericParticleEmitter":
                    emitterType = new HemisphericParticleEmitter();
                    break;
                case "BoxEmitter":
                case "BoxParticleEmitter":
                default:
                    emitterType = new BoxParticleEmitter();
                    break;
            }

            emitterType.parse(parsedParticleSystem.particleEmitterType);
        } else {
            emitterType = new BoxParticleEmitter();
            emitterType.parse(parsedParticleSystem);
        }
        particleSystem.particleEmitterType = emitterType;

        // Animation sheet
        particleSystem.startSpriteCellID = parsedParticleSystem.startSpriteCellID;
        particleSystem.endSpriteCellID = parsedParticleSystem.endSpriteCellID;
        particleSystem.spriteCellWidth = parsedParticleSystem.spriteCellWidth;
        particleSystem.spriteCellHeight = parsedParticleSystem.spriteCellHeight;
        particleSystem.spriteCellChangeSpeed = parsedParticleSystem.spriteCellChangeSpeed;
        particleSystem.spriteRandomStartCell = parsedParticleSystem.spriteRandomStartCell;
    }

    /**
     * Parses a JSON object to create a particle system.
     * @param parsedParticleSystem The JSON object to parse
     * @param scene The scene to create the particle system in
     * @param rootUrl The root url to use to load external dependencies like texture
     * @param doNotStart Ignore the preventAutoStart attribute and does not start
     * @returns the Parsed particle system
     */
    public static Parse(parsedParticleSystem: any, scene: Scene, rootUrl: string, doNotStart = false): ParticleSystem {
        var name = parsedParticleSystem.name;
        var custom: Nullable<Effect> = null;
        var program: any = null;
        if (parsedParticleSystem.customShader) {
            program = parsedParticleSystem.customShader;
            var defines: string = (program.shaderOptions.defines.length > 0) ? program.shaderOptions.defines.join("\n") : "";
            custom = scene.getEngine().createEffectForParticles(program.shaderPath.fragmentElement, program.shaderOptions.uniforms, program.shaderOptions.samplers, defines);
        }
        var particleSystem = new ParticleSystem(name, parsedParticleSystem.capacity, scene, custom, parsedParticleSystem.isAnimationSheetEnabled);
        particleSystem.customShader = program;

        if (parsedParticleSystem.id) {
            particleSystem.id = parsedParticleSystem.id;
        }

        // SubEmitters
        if (parsedParticleSystem.subEmitters) {
            particleSystem.subEmitters = [];
            for (var cell of parsedParticleSystem.subEmitters) {
                let cellArray = [];
                for (var sub of cell) {
                    cellArray.push(SubEmitter.Parse(sub, scene, rootUrl));
                }

                particleSystem.subEmitters.push(cellArray);
            }
        }

        ParticleSystem._Parse(parsedParticleSystem, particleSystem, scene, rootUrl);

        particleSystem.textureMask = Color4.FromArray(parsedParticleSystem.textureMask);

        // Auto start
        if (parsedParticleSystem.preventAutoStart) {
            particleSystem.preventAutoStart = parsedParticleSystem.preventAutoStart;
        }

        if (!doNotStart && !particleSystem.preventAutoStart) {
            particleSystem.start();
        }

        return particleSystem;
    }
}

SubEmitter._ParseParticleSystem = ParticleSystem.Parse;