Babylon.js/src/Particles/babylon.gpuParticleSystem.ts

module BABYLON {
    /**
     * This represents a GPU particle system in Babylon
     * This is the fastest particle system in Babylon as it uses the GPU to update the individual particle data
     * @see https://www.babylonjs-playground.com/#PU4WYI#4
     */
    export class GPUParticleSystem extends BaseParticleSystem implements IDisposable, IParticleSystem, IAnimatable {
        /**
         * The layer mask we are rendering the particles through.
         */
        public layerMask: number = 0x0FFFFFFF;

        private _capacity: number;
        private _activeCount: number;
        private _currentActiveCount: number;
        private _accumulatedCount = 0;
        private _renderEffect: Effect;
        private _updateEffect: Effect;

        private _buffer0: Buffer;
        private _buffer1: Buffer;
        private _spriteBuffer: Buffer;
        private _updateVAO: Array<WebGLVertexArrayObject>;
        private _renderVAO: Array<WebGLVertexArrayObject>;

        private _targetIndex = 0;
        private _sourceBuffer: Buffer;
        private _targetBuffer: Buffer;

        private _engine: Engine;

        private _currentRenderId = -1;    
        private _started = false;    
        private _stopped = false;    

        private _timeDelta = 0;

        private _randomTexture: RawTexture;
        private _randomTexture2: RawTexture;

        private _attributesStrideSize = 21;
        private _updateEffectOptions: EffectCreationOptions;

        private _randomTextureSize: number;
        private _actualFrame = 0;      
        
        private readonly _rawTextureWidth = 256;

        /**
         * Gets a boolean indicating if the GPU particles can be rendered on current browser
         */
        public static get IsSupported(): boolean {
            if (!Engine.LastCreatedEngine) {
                return false;
            }
            return Engine.LastCreatedEngine.webGLVersion > 1;
        }

        /**
        * An event triggered when the system is disposed.
        */
        public onDisposeObservable = new Observable<GPUParticleSystem>();

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

        /**
         * Forces the particle to write their depth information to the depth buffer. This can help preventing other draw calls
         * to override the particles.
         */
        public forceDepthWrite = false;        

        /**
         * Gets or set the number of active particles
         */
        public get activeParticleCount(): number {
            return this._activeCount;
        }

        public set activeParticleCount(value: number) {
            this._activeCount = Math.min(value, this._capacity);
        }

        private _preWarmDone = false;
               
        /**
         * Is this system ready to be used/rendered
         * @return true if the system is ready
         */
        public isReady(): boolean {
            if (!this._updateEffect) {
                this._recreateUpdateEffect();
                this._recreateRenderEffect();
                return false;
            }


            if (!this.emitter || !this._updateEffect.isReady() || !this._imageProcessingConfiguration.isReady() || !this._renderEffect.isReady() || !this.particleTexture || !this.particleTexture.isReady()) {
                return false;
            }

            return true;
        }        

        /**
         * 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;
        }

        /**
         * Starts the particle system and begins to emit
         * @param delay defines the delay in milliseconds before starting the system (0 by default)
         */
        public start(delay = 0): void {
            if (delay) {
                setTimeout(()=> {
                    this.start(0);
                }, delay);
                return;
            }
            this._started = true;
            this._stopped = false;
            this._preWarmDone = false;
        }

        /**
         * Stops the particle system.
         */
        public stop(): void {
            this._stopped = true;
        }

        /**
         * Remove all active particles
         */
        public reset(): void {
            this._releaseBuffers();
            this._releaseVAOs();   
            this._currentActiveCount = 0;         
            this._targetIndex = 0;
        }      
        
        /**
         * Returns the string "GPUParticleSystem"
         * @returns a string containing the class name 
         */
        public getClassName(): string {
            return "GPUParticleSystem";
        }            
               
        private _colorGradientsTexture: RawTexture;

        private _removeGradient(gradient: number, gradients: Nullable<IValueGradient[]>, texture: RawTexture): GPUParticleSystem {
            if (!gradients) {
                return this;
            }

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

            if (texture) {
                texture.dispose();
            }            

            this._releaseBuffers();

            return this;
        }    
        
        /**
         * Adds a new color gradient
         * @param gradient defines the gradient to use (between 0 and 1)
         * @param color 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 the current particle system
         */
        public addColorGradient(gradient: number, color1: Color4, color2?: Color4): GPUParticleSystem {
            if (!this._colorGradients) {
                this._colorGradients = [];
            }

            let colorGradient = new ColorGradient();
            colorGradient.gradient = gradient;
            colorGradient.color1 = color1;
            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;
            });

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

            this._releaseBuffers();            

            return this;
        }

        /**
         * Remove a specific color gradient
         * @param gradient defines the gradient to remove
         * @returns the current particle system
         */
        public removeColorGradient(gradient: number): GPUParticleSystem {
            this._removeGradient(gradient, this._colorGradients, this._colorGradientsTexture);
            (<any>this._colorGradientsTexture) = null;

            return this;
        }    

        private _angularSpeedGradientsTexture: RawTexture;           
        private _sizeGradientsTexture: RawTexture;             
        private _velocityGradientsTexture: RawTexture;    
        private _limitVelocityGradientsTexture: RawTexture;    
        private _dragGradientsTexture: RawTexture;  

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

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

                return 0;
            });

            this._releaseBuffers();               
        }
        
        /**
         * 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
         * @returns the current particle system
         */
        public addSizeGradient(gradient: number, factor: number): GPUParticleSystem {
            if (!this._sizeGradients) {
                this._sizeGradients = [];
            }

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

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

            this._releaseBuffers();                 

            return this;
        }

        /**
         * Remove a specific size gradient
         * @param gradient defines the gradient to remove
         * @returns the current particle system
         */
        public removeSizeGradient(gradient: number): GPUParticleSystem {
            this._removeGradient(gradient, this._sizeGradients, this._sizeGradientsTexture);
            (<any>this._sizeGradientsTexture) = null;

            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    
         * @returns the current particle system     
         */
        public addAngularSpeedGradient(gradient: number, factor: number): GPUParticleSystem {
            if (!this._angularSpeedGradients) {
                this._angularSpeedGradients = [];
            }

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

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

            this._releaseBuffers();   

            return this;
        }

        /**
         * Remove a specific angular speed gradient
         * @param gradient defines the gradient to remove
         * @returns the current particle system
         */
        public removeAngularSpeedGradient(gradient: number): GPUParticleSystem {
            this._removeGradient(gradient, this._angularSpeedGradients, this._angularSpeedGradientsTexture);
            (<any>this._angularSpeedGradientsTexture) = null;

            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    
         * @returns the current particle system     
         */
        public addVelocityGradient(gradient: number, factor: number): GPUParticleSystem {
            if (!this._velocityGradients) {
                this._velocityGradients = [];
            }

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

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

            this._releaseBuffers();   

            return this;
        }

        /**
         * Remove a specific velocity gradient
         * @param gradient defines the gradient to remove
         * @returns the current particle system
         */
        public removeVelocityGradient(gradient: number): GPUParticleSystem {
            this._removeGradient(gradient, this._velocityGradients, this._velocityGradientsTexture);
            (<any>this._velocityGradientsTexture) = null;

            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    
         * @returns the current particle system     
         */
        public addLimitVelocityGradient(gradient: number, factor: number): GPUParticleSystem {
            if (!this._limitVelocityGradients) {
                this._limitVelocityGradients = [];
            }

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

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

            this._releaseBuffers();   

            return this;
        }

        /**
         * Remove a specific limit velocity gradient
         * @param gradient defines the gradient to remove
         * @returns the current particle system
         */
        public removeLimitVelocityGradient(gradient: number): GPUParticleSystem {
            this._removeGradient(gradient, this._limitVelocityGradients, this._limitVelocityGradientsTexture);
            (<any>this._limitVelocityGradientsTexture) = null;

            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    
         * @returns the current particle system     
         */
        public addDragGradient(gradient: number, factor: number): GPUParticleSystem {
            if (!this._dragGradients) {
                this._dragGradients = [];
            }

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

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

            this._releaseBuffers();   

            return this;
        }

        /**
         * Remove a specific drag gradient
         * @param gradient defines the gradient to remove
         * @returns the current particle system
         */
        public removeDragGradient(gradient: number): GPUParticleSystem {
            this._removeGradient(gradient, this._dragGradients, this._dragGradientsTexture);
            (<any>this._dragGradientsTexture) = null;

            return this;
        }   
        
        /**
         * Not supported by GPUParticleSystem
         * @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 {
            // Do nothing as emit rate is not supported by GPUParticleSystem
            return this;
        }

        /**
         * Not supported by GPUParticleSystem
         * @param gradient defines the gradient to remove
         * @returns the current particle system
         */
        public removeEmitRateGradient(gradient: number): IParticleSystem {
            // Do nothing as emit rate is not supported by GPUParticleSystem
            return this;
        } 

        /**
         * Not supported by GPUParticleSystem
         * @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 {
            // Do nothing as start size is not supported by GPUParticleSystem
            return this;
        }

        /**
         * Not supported by GPUParticleSystem
         * @param gradient defines the gradient to remove
         * @returns the current particle system
         */
        public removeStartSizeGradient(gradient: number): IParticleSystem {
            // Do nothing as start size is not supported by GPUParticleSystem
            return this;
        } 

        /**
         * Instantiates a GPU 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 options The options used to create the system
         * @param scene The scene the particle system belongs to
         * @param isAnimationSheetEnabled Must be true if using a spritesheet to animate the particles texture
         */
        constructor(name: string, options: Partial<{
                        capacity: number,
                        randomTextureSize: number
                    }>, scene: Scene, isAnimationSheetEnabled: boolean = false) {
            super(name);
            this._scene = scene || Engine.LastCreatedScene;
            // Setup the default processing configuration to the scene.
            this._attachImageProcessingConfiguration(null);
            
            this._engine = this._scene.getEngine();

            if (!options.randomTextureSize) {
                delete options.randomTextureSize;
            }

            let fullOptions = {
                capacity: 50000,
                randomTextureSize: this._engine.getCaps().maxTextureSize,
                ...options
            };

            var optionsAsNumber = <number>options;
            if (isFinite(optionsAsNumber)) {
                fullOptions.capacity = optionsAsNumber;
            }

            this._capacity = fullOptions.capacity;
            this._activeCount = fullOptions.capacity;
            this._currentActiveCount = 0;
            this._isAnimationSheetEnabled = isAnimationSheetEnabled;

            this._scene.particleSystems.push(this);

            this._updateEffectOptions = {
                attributes: ["position", "age", "life", "seed", "size", "color", "direction", "initialDirection", "angle", "cellIndex", "cellStartOffset"],
                uniformsNames: ["currentCount", "timeDelta", "emitterWM", "lifeTime", "color1", "color2", "sizeRange", "scaleRange","gravity", "emitPower",
                                "direction1", "direction2", "minEmitBox", "maxEmitBox", "radius", "directionRandomizer", "height", "coneAngle", "stopFactor", 
                                "angleRange", "radiusRange", "cellInfos", "noiseStrength", "limitVelocityDamping"],
                uniformBuffersNames: [],
                samplers:["randomSampler", "randomSampler2", "sizeGradientSampler", "angularSpeedGradientSampler", "velocityGradientSampler", "limitVelocityGradientSampler", "noiseSampler", "dragGradientSampler"],
                defines: "",
                fallbacks: null,  
                onCompiled: null,
                onError: null,
                indexParameters: null,
                maxSimultaneousLights: 0,                                                      
                transformFeedbackVaryings: []
            };

            this.particleEmitterType = new BoxParticleEmitter();

            // Random data
            var maxTextureSize = Math.min(this._engine.getCaps().maxTextureSize, fullOptions.randomTextureSize);
            var d = [];
            for (var i = 0; i < maxTextureSize; ++i) {
                d.push(Math.random());
                d.push(Math.random());
                d.push(Math.random());
                d.push(Math.random());
            }
            this._randomTexture = new RawTexture(new Float32Array(d), maxTextureSize, 1, Engine.TEXTUREFORMAT_RGBA, this._scene, false, false, Texture.NEAREST_SAMPLINGMODE, Engine.TEXTURETYPE_FLOAT);
            this._randomTexture.wrapU = Texture.WRAP_ADDRESSMODE;
            this._randomTexture.wrapV = Texture.WRAP_ADDRESSMODE;

            d = [];
            for (var i = 0; i < maxTextureSize; ++i) {
                d.push(Math.random());
                d.push(Math.random());
                d.push(Math.random());
                d.push(Math.random());
            }
            this._randomTexture2 = new RawTexture(new Float32Array(d), maxTextureSize, 1, Engine.TEXTUREFORMAT_RGBA, this._scene, false, false, Texture.NEAREST_SAMPLINGMODE, Engine.TEXTURETYPE_FLOAT);
            this._randomTexture2.wrapU = Texture.WRAP_ADDRESSMODE;
            this._randomTexture2.wrapV = Texture.WRAP_ADDRESSMODE;

            this._randomTextureSize = maxTextureSize;
        }

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

        private _createUpdateVAO(source: Buffer): WebGLVertexArrayObject {            
            let updateVertexBuffers: {[key: string]: VertexBuffer} = {};
            updateVertexBuffers["position"] = source.createVertexBuffer("position", 0, 3);
            updateVertexBuffers["age"] = source.createVertexBuffer("age", 3, 1);
            updateVertexBuffers["life"] = source.createVertexBuffer("life", 4, 1);
            updateVertexBuffers["seed"] = source.createVertexBuffer("seed", 5, 4);
            updateVertexBuffers["size"] = source.createVertexBuffer("size", 9, 3);
            let offset = 12;

            if (!this._colorGradientsTexture) {
                updateVertexBuffers["color"] = source.createVertexBuffer("color", offset, 4);
                offset += 4;
            }

            updateVertexBuffers["direction"] = source.createVertexBuffer("direction", offset, 3);
            offset += 3

            if (!this._isBillboardBased) {
                updateVertexBuffers["initialDirection"] = source.createVertexBuffer("initialDirection", offset, 3);
                offset += 3;
            }

            if (this._angularSpeedGradientsTexture) {
                updateVertexBuffers["angle"] = source.createVertexBuffer("angle", offset, 1);
                offset += 1;
            } else {
                updateVertexBuffers["angle"] = source.createVertexBuffer("angle", offset, 2);
                offset += 2;
            }

            if (this._isAnimationSheetEnabled) {
                updateVertexBuffers["cellIndex"] = source.createVertexBuffer("cellIndex", offset, 1);
                offset += 1;
                if (this.spriteRandomStartCell) {
                    updateVertexBuffers["cellStartOffset"] = source.createVertexBuffer("cellStartOffset", offset, 1);
                    offset += 1;
                }
            }            
           
            let vao = this._engine.recordVertexArrayObject(updateVertexBuffers, null, this._updateEffect);
            this._engine.bindArrayBuffer(null);

            return vao;
        }

        private _createRenderVAO(source: Buffer, spriteSource: Buffer): WebGLVertexArrayObject {            
            let renderVertexBuffers: {[key: string]: VertexBuffer} = {};
            renderVertexBuffers["position"] = source.createVertexBuffer("position", 0, 3, this._attributesStrideSize, true);
            renderVertexBuffers["age"] = source.createVertexBuffer("age", 3, 1, this._attributesStrideSize, true);
            renderVertexBuffers["life"] = source.createVertexBuffer("life", 4, 1, this._attributesStrideSize, true);
            renderVertexBuffers["size"] = source.createVertexBuffer("size", 9, 3, this._attributesStrideSize, true);      
            
            let offset = 12;

            if (!this._colorGradientsTexture) {
                renderVertexBuffers["color"] = source.createVertexBuffer("color", offset, 4, this._attributesStrideSize, true);
                offset += 4;
            }
            
            offset += 3; // Direction

            if (!this._isBillboardBased) {
                renderVertexBuffers["initialDirection"] = source.createVertexBuffer("initialDirection", offset, 3, this._attributesStrideSize, true);
                offset += 3;
            }

            renderVertexBuffers["angle"] = source.createVertexBuffer("angle", offset, 1, this._attributesStrideSize, true);
            if (this._angularSpeedGradientsTexture) {
                offset++;
            } else {
                offset += 2;
            }

            if (this._isAnimationSheetEnabled) {
                renderVertexBuffers["cellIndex"] = source.createVertexBuffer("cellIndex", offset, 1, this._attributesStrideSize, true);
                offset += 1;
                if (this.spriteRandomStartCell) {
                    renderVertexBuffers["cellStartOffset"] = source.createVertexBuffer("cellStartOffset", offset, 1, this._attributesStrideSize, true);
                    offset += 1;
                }
            }               

            renderVertexBuffers["offset"] = spriteSource.createVertexBuffer("offset", 0, 2);
            renderVertexBuffers["uv"] = spriteSource.createVertexBuffer("uv", 2, 2);
           
            let vao = this._engine.recordVertexArrayObject(renderVertexBuffers, null, this._renderEffect);
            this._engine.bindArrayBuffer(null);

            return vao;
        }        
        
        private _initialize(force = false): void {
            if (this._buffer0 && !force) {
                return;
            }

            let engine = this._scene.getEngine();
            var data = new Array<float>();

            if (!this.isBillboardBased) {
                this._attributesStrideSize += 3;
            }

            if (this._colorGradientsTexture) {
                this._attributesStrideSize -= 4;
            }

            if (this._angularSpeedGradientsTexture) {
                this._attributesStrideSize -= 1;
            }            

            if (this._isAnimationSheetEnabled) {
                this._attributesStrideSize += 1;
                if (this.spriteRandomStartCell) {
                    this._attributesStrideSize += 1;
                }
            }            

            for (var particleIndex = 0; particleIndex < this._capacity; particleIndex++) {
                // position
                data.push(0.0);
                data.push(0.0);
                data.push(0.0);

                // Age and life
                data.push(0.0); // create the particle as a dead one to create a new one at start
                data.push(0.0);

                // Seed
                data.push(Math.random());
                data.push(Math.random());
                data.push(Math.random());
                data.push(Math.random());

                // Size
                data.push(0.0);
                data.push(0.0);
                data.push(0.0);

                if (!this._colorGradientsTexture) {
                    // color
                    data.push(0.0);
                    data.push(0.0);
                    data.push(0.0);                     
                    data.push(0.0); 
                }

                // direction
                data.push(0.0);
                data.push(0.0);
                data.push(0.0);  

                if (!this.isBillboardBased) {
                    // initialDirection
                    data.push(0.0);
                    data.push(0.0);
                    data.push(0.0);  
                }

                // angle
                data.push(0.0);  

                if (!this._angularSpeedGradientsTexture) {
                    data.push(0.0); 
                }

                if (this._isAnimationSheetEnabled) {
                    data.push(0.0); 
                    if (this.spriteRandomStartCell) {
                        data.push(0.0); 
                    }
                }                
            }

            // Sprite data
            var spriteData = new Float32Array([0.5, 0.5,  1, 1,  
                                              -0.5, 0.5,  0, 1,
                                             -0.5, -0.5,  0, 0,   
                                             0.5, -0.5,  1, 0]);

            // Buffers
            this._buffer0 = new Buffer(engine, data, false, this._attributesStrideSize);
            this._buffer1 = new Buffer(engine, data, false, this._attributesStrideSize);
            this._spriteBuffer = new Buffer(engine, spriteData, false, 4);                                      

            // Update VAO
            this._updateVAO = [];
            this._updateVAO.push(this._createUpdateVAO(this._buffer0));
            this._updateVAO.push(this._createUpdateVAO(this._buffer1));

            // Render VAO
            this._renderVAO = [];
            this._renderVAO.push(this._createRenderVAO(this._buffer1, this._spriteBuffer));
            this._renderVAO.push(this._createRenderVAO(this._buffer0, this._spriteBuffer));

            // Links
            this._sourceBuffer = this._buffer0;
            this._targetBuffer = this._buffer1;

        }

        /** @hidden */
        public _recreateUpdateEffect() {
            let defines = this.particleEmitterType ? this.particleEmitterType.getEffectDefines() : "";

            if (this._isBillboardBased) {
                defines += "\n#define BILLBOARD";
            }   

            if (this._colorGradientsTexture) {
                defines += "\n#define COLORGRADIENTS";
            }        
            
            if (this._sizeGradientsTexture) {
                defines += "\n#define SIZEGRADIENTS";
            }     

            if (this._angularSpeedGradientsTexture) {
                defines += "\n#define ANGULARSPEEDGRADIENTS";
            }               
            
            if (this._velocityGradientsTexture) {
                defines += "\n#define VELOCITYGRADIENTS";
            }        

            if (this._limitVelocityGradientsTexture) {
                defines += "\n#define LIMITVELOCITYGRADIENTS";
            }                
            
            if (this._dragGradientsTexture) {
                defines += "\n#define DRAGGRADIENTS";
            }              
            
            if (this.isAnimationSheetEnabled) {
                defines += "\n#define ANIMATESHEET";
                if (this.spriteRandomStartCell) {
                    defines += "\n#define ANIMATESHEETRANDOMSTART";
                }
            }   
            
            if (this.noiseTexture) {
                defines += "\n#define NOISE";
            }

            if (this._updateEffect && this._updateEffectOptions.defines === defines) {
                return;
            }

            this._updateEffectOptions.transformFeedbackVaryings = ["outPosition", "outAge", "outLife", "outSeed", "outSize"];           

            if (!this._colorGradientsTexture) {
                this._updateEffectOptions.transformFeedbackVaryings.push("outColor");
            }

            this._updateEffectOptions.transformFeedbackVaryings.push("outDirection");

            if (!this._isBillboardBased) {
                this._updateEffectOptions.transformFeedbackVaryings.push("outInitialDirection");
            }

            this._updateEffectOptions.transformFeedbackVaryings.push("outAngle");

            if (this.isAnimationSheetEnabled) {
                this._updateEffectOptions.transformFeedbackVaryings.push("outCellIndex");
                if (this.spriteRandomStartCell) {
                    this._updateEffectOptions.transformFeedbackVaryings.push("outCellStartOffset");
                }
            }               

            this._updateEffectOptions.defines = defines;
            this._updateEffect = new Effect("gpuUpdateParticles", this._updateEffectOptions, this._scene.getEngine());   
        }

        /** @hidden */
        public _recreateRenderEffect() {
            let defines = "";
            if (this._scene.clipPlane) {
                defines = "\n#define CLIPPLANE";
            }
            if (this._scene.clipPlane2) {
                defines = "\n#define CLIPPLANE2";
            }
            if (this._scene.clipPlane3) {
                defines = "\n#define CLIPPLANE3";
            }
            if (this._scene.clipPlane4) {
                defines = "\n#define CLIPPLANE4";
            }

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

            if (this._isBillboardBased) {
                defines += "\n#define BILLBOARD";

                switch (this.billboardMode) {
                    case AbstractMesh.BILLBOARDMODE_Y:
                        defines += "\n#define BILLBOARDY";
                        break;
                    case AbstractMesh.BILLBOARDMODE_ALL:
                    default:
                        break;
                }                
            }         
            
            if (this._colorGradientsTexture) {
                defines += "\n#define COLORGRADIENTS";
            }   

            if (this.isAnimationSheetEnabled) {
                defines += "\n#define ANIMATESHEET";
            }                 

            if (this._imageProcessingConfiguration) {
                this._imageProcessingConfiguration.prepareDefines(this._imageProcessingConfigurationDefines);
                defines += "\n" + this._imageProcessingConfigurationDefines.toString();
            }

            if (this._renderEffect && this._renderEffect.defines === defines) {
                return;
            }

            var uniforms = ["view", "projection", "colorDead", "invView", "vClipPlane", "vClipPlane2", "vClipPlane3", "vClipPlane4", "sheetInfos", "translationPivot", "eyePosition"];
            var samplers = ["textureSampler", "colorGradientSampler"];

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

            this._renderEffect = new Effect("gpuRenderParticles", 
                                            ["position", "age", "life", "size", "color", "offset", "uv", "initialDirection", "angle", "cellIndex"], 
                                            uniforms, 
                                            samplers, this._scene.getEngine(), defines);
        }        

        /**
         * Animates the particle system for the current frame by emitting new particles and or animating the living ones.
         * @param preWarm defines if we are in the pre-warmimg phase
         */
        public animate(preWarm = false): void {           
            this._timeDelta = this.updateSpeed * (preWarm ? this.preWarmStepOffset : this._scene.getAnimationRatio());
            this._actualFrame += this._timeDelta;

            if (!this._stopped) {
                if (this.targetStopDuration && this._actualFrame >= this.targetStopDuration) {
                    this.stop();
                }
            }             
        }    

        private _createFactorGradientTexture(factorGradients: Nullable<IValueGradient[]>, textureName: string) {
            let texture:RawTexture = (<any>this)[textureName];

            if (!factorGradients || !factorGradients.length || texture) {
                return;
            }

            let data = new Float32Array(this._rawTextureWidth);

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

                Tools.GetCurrentGradient(ratio, factorGradients, (currentGradient, nextGradient, scale) => {
                    data[x] = Scalar.Lerp((<FactorGradient>currentGradient).factor1, (<FactorGradient>nextGradient).factor1, scale);
                });
            }

            (<any>this)[textureName] = RawTexture.CreateRTexture(data, this._rawTextureWidth, 1, this._scene, false, false, Texture.NEAREST_SAMPLINGMODE);
        }            

        private _createSizeGradientTexture() {
            this._createFactorGradientTexture(this._sizeGradients, "_sizeGradientsTexture");
        }     
        
        private _createAngularSpeedGradientTexture() {
            this._createFactorGradientTexture(this._angularSpeedGradients, "_angularSpeedGradientsTexture");
        }     

        private _createVelocityGradientTexture() {
            this._createFactorGradientTexture(this._velocityGradients, "_velocityGradientsTexture");
        }          

        private _createLimitVelocityGradientTexture() {
            this._createFactorGradientTexture(this._limitVelocityGradients, "_limitVelocityGradientsTexture");
        }          

        private _createDragGradientTexture() {
            this._createFactorGradientTexture(this._dragGradients, "_dragGradientsTexture");
        }            
            
        private _createColorGradientTexture() {
            if (!this._colorGradients || !this._colorGradients.length || this._colorGradientsTexture) {
                return;
            }

            let data = new Uint8Array(this._rawTextureWidth * 4);
            let tmpColor = Tmp.Color4[0];

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

                Tools.GetCurrentGradient(ratio, this._colorGradients, (currentGradient, nextGradient, scale) => {

                    Color4.LerpToRef((<ColorGradient>currentGradient).color1, (<ColorGradient>nextGradient).color1, 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] = tmpColor.a * 255;
                });

            }

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

        /**
         * Renders the particle system in its current state
         * @param preWarm defines if the system should only update the particles but not render them
         * @returns the current number of particles
         */
        public render(preWarm = false): number {
            if (!this._started) {
                return 0;
            }

            this._createColorGradientTexture();
            this._createSizeGradientTexture();
            this._createAngularSpeedGradientTexture();
            this._createVelocityGradientTexture();
            this._createLimitVelocityGradientTexture();
            this._createDragGradientTexture();

            this._recreateUpdateEffect();
            this._recreateRenderEffect();

            if (!this.isReady()) {
                return 0;
            }

            if (!preWarm) {
                if (!this._preWarmDone && this.preWarmCycles) {                
                    for (var index = 0; index < this.preWarmCycles; index++) {
                        this.animate(true);
                        this.render(true);
                    }

                    this._preWarmDone = true;
                }

                if (this._currentRenderId === this._scene.getRenderId()) {
                    return 0;
                }

                this._currentRenderId = this._scene.getRenderId();      
            }
            
            // Get everything ready to render
            this._initialize();

            this._accumulatedCount += this.emitRate * this._timeDelta;
            if (this._accumulatedCount > 1) {
                var intPart = this._accumulatedCount | 0;
                this._accumulatedCount -= intPart;
                this._currentActiveCount = Math.min(this._activeCount, this._currentActiveCount + intPart);
            }

            if (!this._currentActiveCount) {
                return 0;
            }
            
            // Enable update effect
            this._engine.enableEffect(this._updateEffect);
            this._engine.setState(false);    
            
            this._updateEffect.setFloat("currentCount", this._currentActiveCount);
            this._updateEffect.setFloat("timeDelta", this._timeDelta);
            this._updateEffect.setFloat("stopFactor", this._stopped ? 0 : 1);
            this._updateEffect.setTexture("randomSampler", this._randomTexture);
            this._updateEffect.setTexture("randomSampler2", this._randomTexture2);
            this._updateEffect.setFloat2("lifeTime", this.minLifeTime, this.maxLifeTime);
            this._updateEffect.setFloat2("emitPower", this.minEmitPower, this.maxEmitPower);
            if (!this._colorGradientsTexture) {            
                this._updateEffect.setDirectColor4("color1", this.color1);
                this._updateEffect.setDirectColor4("color2", this.color2);
            }
            this._updateEffect.setFloat2("sizeRange", this.minSize, this.maxSize);
            this._updateEffect.setFloat4("scaleRange", this.minScaleX, this.maxScaleX, this.minScaleY, this.maxScaleY);
            this._updateEffect.setFloat4("angleRange", this.minAngularSpeed, this.maxAngularSpeed, this.minInitialRotation, this.maxInitialRotation);
            this._updateEffect.setVector3("gravity", this.gravity);

            if (this._sizeGradientsTexture) {      
                this._updateEffect.setTexture("sizeGradientSampler", this._sizeGradientsTexture);      
            }

            if (this._angularSpeedGradientsTexture) {      
                this._updateEffect.setTexture("angularSpeedGradientSampler", this._angularSpeedGradientsTexture);      
            }

            if (this._velocityGradientsTexture) {      
                this._updateEffect.setTexture("velocityGradientSampler", this._velocityGradientsTexture);      
            }

            if (this._limitVelocityGradientsTexture) {      
                this._updateEffect.setTexture("limitVelocityGradientSampler", this._limitVelocityGradientsTexture);  
                this._updateEffect.setFloat("limitVelocityDamping", this.limitVelocityDamping);    
            }            

            if (this._dragGradientsTexture) {      
                this._updateEffect.setTexture("dragGradientSampler", this._dragGradientsTexture);      
            }

            if (this.particleEmitterType) {
                this.particleEmitterType.applyToShader(this._updateEffect);
            }
            if (this._isAnimationSheetEnabled) {
                this._updateEffect.setFloat3("cellInfos", this.startSpriteCellID, this.endSpriteCellID, this.spriteCellChangeSpeed);
            }        
            
            if (this.noiseTexture) {
                this._updateEffect.setTexture("noiseSampler", this.noiseTexture);  
                this._updateEffect.setVector3("noiseStrength", this.noiseStrength);    
            }

            let emitterWM: Matrix;
            if ((<AbstractMesh>this.emitter).position) {
                var emitterMesh = (<AbstractMesh>this.emitter);
                emitterWM = emitterMesh.getWorldMatrix();
            } else {
                var emitterPosition = (<Vector3>this.emitter);
                emitterWM = Matrix.Translation(emitterPosition.x, emitterPosition.y, emitterPosition.z);
            }            
            this._updateEffect.setMatrix("emitterWM", emitterWM);

            // Bind source VAO
            this._engine.bindVertexArrayObject(this._updateVAO[this._targetIndex], null);

            // Update
            this._engine.bindTransformFeedbackBuffer(this._targetBuffer.getBuffer());
            this._engine.setRasterizerState(false);
            this._engine.beginTransformFeedback(true);
            this._engine.drawArraysType(Material.PointListDrawMode, 0, this._currentActiveCount);
            this._engine.endTransformFeedback();
            this._engine.setRasterizerState(true);
            this._engine.bindTransformFeedbackBuffer(null);

            if (!preWarm) {
                // Enable render effect
                this._engine.enableEffect(this._renderEffect);
                let viewMatrix = this._scene.getViewMatrix();
                this._renderEffect.setMatrix("view", viewMatrix);
                this._renderEffect.setMatrix("projection", this._scene.getProjectionMatrix());
                this._renderEffect.setTexture("textureSampler", this.particleTexture);
                this._renderEffect.setVector2("translationPivot", this.translationPivot);
                if (this._colorGradientsTexture) {
                    this._renderEffect.setTexture("colorGradientSampler", this._colorGradientsTexture);
                } else {
                    this._renderEffect.setDirectColor4("colorDead", this.colorDead);
                }

                if (this._isAnimationSheetEnabled && this.particleTexture) {
                    let baseSize = this.particleTexture.getBaseSize();
                    this._renderEffect.setFloat3("sheetInfos", this.spriteCellWidth / baseSize.width, this.spriteCellHeight / baseSize.height, baseSize.width / this.spriteCellWidth);
                }

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

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

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

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

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

                // Bind source VAO
                this._engine.bindVertexArrayObject(this._renderVAO[this._targetIndex], null);

                // Render
                this._engine.drawArraysType(Material.TriangleFanDrawMode, 0, 4, this._currentActiveCount);   
                this._engine.setAlphaMode(Engine.ALPHA_DISABLE);         
            }
            // Switch VAOs
            this._targetIndex++;
            if (this._targetIndex === 2) {
                this._targetIndex = 0;
            }

            // Switch buffers
            let tmpBuffer = this._sourceBuffer;
            this._sourceBuffer = this._targetBuffer;
            this._targetBuffer = tmpBuffer;     
            
            return this._currentActiveCount;
        }

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

        private _releaseBuffers() {
            if (this._buffer0) {
                this._buffer0.dispose();
                (<any>this._buffer0) = null;
            }
            if (this._buffer1) {
                this._buffer1.dispose();
                (<any>this._buffer1) = null;
            }
            if (this._spriteBuffer) {
                this._spriteBuffer.dispose();
                (<any>this._spriteBuffer) = null;
            }            
        }

        private _releaseVAOs() {
            if (!this._updateVAO) {
                return;
            }
            
            for (var index = 0; index < this._updateVAO.length; index++) {
                this._engine.releaseVertexArrayObject(this._updateVAO[index]);
            }
            this._updateVAO = [];

            for (var index = 0; index < this._renderVAO.length; index++) {
                this._engine.releaseVertexArrayObject(this._renderVAO[index]);
            }
            this._renderVAO = [];   
        }

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

            this._releaseBuffers();
            this._releaseVAOs();

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

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

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

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

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

            if (this._randomTexture2) {
                this._randomTexture2.dispose();
                (<any>this._randomTexture2) = null;
            }            

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

            // Callback
            this.onDisposeObservable.notifyObservers(this);
            this.onDisposeObservable.clear();
        }
        /**
         * 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): GPUParticleSystem {
            var result = new GPUParticleSystem(name, {capacity: this._capacity, randomTextureSize: this._randomTextureSize}, this._scene);

            Tools.DeepCopy(this, result);

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

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

            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.activeParticleCount = this.activeParticleCount;

            return serializationObject;            
        }

        /**
         * Parses a JSON object to create a GPU 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
         * @returns the parsed GPU particle system
         */
        public static Parse(parsedParticleSystem: any, scene: Scene, rootUrl: string): GPUParticleSystem {
            var name = parsedParticleSystem.name;
            var particleSystem = new GPUParticleSystem(name, {capacity: parsedParticleSystem.capacity, randomTextureSize: parsedParticleSystem.randomTextureSize}, scene);

            if (parsedParticleSystem.activeParticleCount) {
                particleSystem.activeParticleCount = parsedParticleSystem.activeParticleCount;
            }
            ParticleSystem._Parse(parsedParticleSystem, particleSystem, scene, rootUrl);

            return particleSystem;
        }        
    }
}