canvas.height * 4;

            // to read from webgl canvas
            //this.rgba = new Uint8ClampedArray( this.bufferSize );

            // to read from our float ping pong buffers
            this.rgba = new Float32Array( this.bufferSize );

            // Create a buffer to store the pixel data to test async reading of pixels
            this.pbo = gl.createBuffer();
            gl.bindBuffer( gl.PIXEL_PACK_BUFFER, this.pbo );
            gl.bufferData( gl.PIXEL_PACK_BUFFER, this.bufferSize, gl.STATI