/*
* Written by Hao Wu
*
*/
////////////////COPYRIGHT DECLARATION//////////////////////
//////
////// COPYRIGHT GUANYU HE AND HAO WU, 2013
////// ALL THE FOLLOWING CODE IS PROTECTED BY THE COPYRIGHT
//////
////// THE CODE IN THIS FILE CANNOT BE REUSED OUTSIDE CIS565 GPU PROGRAMMING COURSE
////// IN UNIVERSITY OF PENNSYLVANIA UNLESS SPECIAL AUTHORIZATION.
//////
////// CONTACT INFO: heguanyu9037@gmail.com
////// wuhao1117@gmail.com
//////
////////////////FILE INFO ///////////////////////////////
//////
////// FAST FOURIER TRANSFORMATION
////// INITIALIZATION THE SPECTRUM TEXTURE
////// AND RELATED FRAME BUFFER
//////
////////////////////////////////////////////////////////////
var fftHorizontalProgram;
var fftVerticalProgram;
var spectrumFramebuffer;
var spectrumTextureA;
var spectrumTextureB;
var initialSpectrumTex;
var butterflyTextures;
var heightFieldTex;
var numFFTStages;
function initFFTHorizontalShader() {
var vertexShader = getShader(gl, "vs_quad");
var fragmentShader = getShader(gl, "fs_fftHorizontal");
fftHorizontalProgram = gl.createProgram();
gl.attachShader(fftHorizontalProgram, vertexShader);
gl.attachShader(fftHorizontalProgram, fragmentShader);
gl.linkProgram(fftHorizontalProgram);
if (!gl.getProgramParameter(fftHorizontalProgram, gl.LINK_STATUS)) {
alert("Could not initialise FFT Horizontal shader");
}
fftHorizontalProgram.vertexPositionAttribute = gl.getAttribLocation(fftHorizontalProgram, "position");
fftHorizontalProgram.fftDataUniform = gl.getUniformLocation(fftHorizontalProgram, "u_fftData");
fftHorizontalProgram.butterflyUniform = gl.getUniformLocation(fftHorizontalProgram, "u_butterflyData");
}
function initFFTVerticalShader() {
var vertexShader = getShader(gl, "vs_quad");
var fragmentShader = getShader(gl, "fs_fftVertical");
fftVerticalProgram = gl.createProgram();
gl.attachShader(fftVerticalProgram, vertexShader);
gl.attachShader(fftVerticalProgram, fragmentShader);
gl.linkProgram(fftVerticalProgram);
if (!gl.getProgramParameter(fftVerticalProgram, gl.LINK_STATUS)) {
alert("Could not initialise FFT Vertical shader");
}
fftVerticalProgram.vertexPositionAttribute = gl.getAttribLocation(fftVerticalProgram, "position");
fftVerticalProgram.fftDataUniform = gl.getUniformLocation(fftVerticalProgram, "u_fftData");
fftVerticalProgram.butterflyUniform = gl.getUniformLocation(fftVerticalProgram, "u_butterflyData");
}
function initFFTFramebuffer()
{
spectrumFramebuffer = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, spectrumFramebuffer);
spectrumFramebuffer.width = meshSize;
spectrumFramebuffer.height = meshSize;
spectrumTextureA = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, spectrumTextureA);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, spectrumFramebuffer.width, spectrumFramebuffer.height, 0, gl.RGBA, gl.FLOAT, null);
spectrumTextureB = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, spectrumTextureB);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, spectrumFramebuffer.width, spectrumFramebuffer.height, 0, gl.RGBA, gl.FLOAT, null);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, spectrumTextureA, 0);
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE) {
throw new Error("gl.checkFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE");
}
gl.bindTexture(gl.TEXTURE_2D, null);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
}
function bitReverse(x, numFFTStages)
{
x = (((x & 0xaaaaaaaa) >> 1) | ((x & 0x55555555) << 1));
x = (((x & 0xcccccccc) >> 2) | ((x & 0x33333333) << 2));
x = (((x & 0xf0f0f0f0) >> 4) | ((x & 0x0f0f0f0f) << 4));
x = (((x & 0xff00ff00) >> 8) | ((x & 0x00ff00ff) << 8));
x = ((x >> 16) | (x << 16));
x >>>= 32 - numFFTStages;
return x;
}
function initButterflyTextures()
{
// initialize butterfly indices and weights for every stage
numFFTStages = Math.log(meshSize)/Math.LN2;
var delta = 1.0/meshSize;
butterflyTextures = new Array(numFFTStages);
for(var n = 0; n < butterflyTextures.length; ++n)
{
var butterflyArray = new Float32Array(meshSize*meshSize*4);
var k = 0, k0 = 0;
var exp = Math.pow(2, numFFTStages - n - 1);
var stepNext = Math.pow(2, n+1);
var stepThis = 0.5*stepNext;
// compute for the first row
for(var m = 0; m < stepThis; ++m) // loop through butterflies with different weights
{
k = m*4;
for(var l = m; l < meshSize; l += stepNext, k += stepNext*4) // loop through butterflies with same weights
{
if(n != 0)
{
// indices for upper operand of butterfly
butterflyArray[k] = (l + 0.5)*delta ; // index (stored as texture coordinates) of Source1
butterflyArray[k+1] = (l + stepThis + 0.5)*delta; // index (stored as texture coordinates) of Source2
// indices for lower operand of butterfly
butterflyArray[k+stepThis*4] = (l + 0.5)*delta ; // index (stored as texture coordinates) of Source1
butterflyArray[k+stepThis*4+1] = (l + stepThis + 0.5)*delta; // index (stored as texture coordinates) of Source2
}
else // scramble the index order for the first stage based on bit reversal
{
// indices for upper operand of butterfly
butterflyArray[k] = (bitReverse(l, numFFTStages)+ 0.5)*delta ; // index (stored as texture coordinates) of Source1
butterflyArray[k+1] = (bitReverse(l + stepThis, numFFTStages) + 0.5)*delta; // index (stored as texture coordinates) of Source2
// indices for lower operand of butterfly
butterflyArray[k+stepThis*4] = (bitReverse(l, numFFTStages) + 0.5)*delta ; // index (stored as texture coordinates) of Source1
butterflyArray[k+stepThis*4+1] = (bitReverse(l + stepThis, numFFTStages) + 0.5)*delta; // index (stored as texture coordinates) of Source2
}
}
}
k = 2;
for(var i = 0; i < meshSize; i++, k += 2)
{
/*
* Source1 ---------- - += Output1
* - -
* -
* - -
* Source2 * weight-- - += Output2
*
* For Source1, weight is stored as it is
* For Source2, weight is stored as -weight
*
*/
var r = (i * exp) % meshSize;
butterflyArray[k++] = Math.cos(2*Math.PI*r/meshSize); // real part of weight
butterflyArray[k++] = Math.sin(2*Math.PI*r/meshSize); // imaginary part of weight
}
// copy the first row to every row
k = 4*meshSize;
for(var j = 1; j < meshSize; j++)
{
k0 = 0;
for(var i = 0; i < meshSize; i++)
{
butterflyArray[k++] = butterflyArray[k0++]; // index (stored as texture coordinates) of Source1
butterflyArray[k++] = butterflyArray[k0++]; // index (stored as texture coordinates) of Source2
butterflyArray[k++] = butterflyArray[k0++]; // real part of weight
butterflyArray[k++] = butterflyArray[k0++]; // imaginary part of weight
}
}
butterflyTextures[n] = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, butterflyTextures[n]);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, meshSize, meshSize, 0, gl.RGBA, gl.FLOAT, butterflyArray);
}
}
function executeFFTStage(sourceData, butterflyData, framebuffer)
{
}