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/** \file smoke/intern/FFT_NOISE.h
* \ingroup smoke
*/
//////////////////////////////////////////////////////////////////////
// This file is part of Wavelet Turbulence.
//
// Wavelet Turbulence is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Wavelet Turbulence is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Wavelet Turbulence. If not, see <http://www.gnu.org/licenses/>.
//
// Copyright 2008 Theodore Kim and Nils Thuerey
//
/////////////////////////////////////////////////////////////////////////
//
#ifndef FFT_NOISE_H_
#define FFT_NOISE_H_
#ifdef WITH_FFTW3
#include <iostream>
#include <fftw3.h>
#include <MERSENNETWISTER.h>
#include "WAVELET_NOISE.h"
#ifndef M_PI
#define M_PI 3.14159265
#endif
/////////////////////////////////////////////////////////////////////////
// shift spectrum to the format that FFTW expects
/////////////////////////////////////////////////////////////////////////
static void shift3D(float*& field, int xRes, int yRes, int zRes)
{
int xHalf = xRes / 2;
int yHalf = yRes / 2;
int zHalf = zRes / 2;
// int slabSize = xRes * yRes;
for (int z = 0; z < zHalf; z++)
for (int y = 0; y < yHalf; y++)
for (int x = 0; x < xHalf; x++)
{
int index = x + y * xRes + z * xRes * yRes;
float temp;
int xSwap = xHalf;
int ySwap = yHalf * xRes;
int zSwap = zHalf * xRes * yRes;
// [0,0,0] to [1,1,1]
temp = field[index];
field[index] = field[index + xSwap + ySwap + zSwap];
field[index + xSwap + ySwap + zSwap] = temp;
// [1,0,0] to [0,1,1]
temp = field[index + xSwap];
field[index + xSwap] = field[index + ySwap + zSwap];
field[index + ySwap + zSwap] = temp;
// [0,1,0] to [1,0,1]
temp = field[index + ySwap];
field[index + ySwap] = field[index + xSwap + zSwap];
field[index + xSwap + zSwap] = temp;
// [0,0,1] to [1,1,0]
temp = field[index + zSwap];
field[index + zSwap] = field[index + xSwap + ySwap];
field[index + xSwap + ySwap] = temp;
}
}
static void generatTile_FFT(float* const noiseTileData, std::string filename)
{
if (loadTile(noiseTileData, filename)) return;
int res = NOISE_TILE_SIZE;
int xRes = res;
int yRes = res;
int zRes = res;
int totalCells = xRes * yRes * zRes;
// create and shift the filter
float* filter = new float[totalCells];
for (int z = 0; z < zRes; z++)
for (int y = 0; y < yRes; y++)
for (int x = 0; x < xRes; x++)
{
int index = x + y * xRes + z * xRes * yRes;
float diff[] = {abs(x - xRes/2),
abs(y - yRes/2),
abs(z - zRes/2)};
float radius = sqrtf(diff[0] * diff[0] +
diff[1] * diff[1] +
diff[2] * diff[2]) / (xRes / 2);
radius *= M_PI;
float H = cos((M_PI / 2.0f) * log(4.0f * radius / M_PI) / log(2.0f));
H = H * H;
float filtered = H;
// clamp everything outside the wanted band
if (radius >= M_PI / 2.0f)
filtered = 0.0f;
// make sure to capture all low frequencies
if (radius <= M_PI / 4.0f)
filtered = 1.0f;
filter[index] = filtered;
}
shift3D(filter, xRes, yRes, zRes);
// create the noise
float* noise = new float[totalCells];
int index = 0;
MTRand twister;
for (int z = 0; z < zRes; z++)
for (int y = 0; y < yRes; y++)
for (int x = 0; x < xRes; x++, index++)
noise[index] = twister.randNorm();
// create padded field
fftw_complex* forward = (fftw_complex*)fftw_malloc(sizeof(fftw_complex) * totalCells);
// init padded field
index = 0;
for (int z = 0; z < zRes; z++)
for (int y = 0; y < yRes; y++)
for (int x = 0; x < xRes; x++, index++)
{
forward[index][0] = noise[index];
forward[index][1] = 0.0f;
}
// forward FFT
fftw_complex* backward = (fftw_complex*)fftw_malloc(sizeof(fftw_complex) * totalCells);
fftw_plan forwardPlan = fftw_plan_dft_3d(xRes, yRes, zRes, forward, backward, FFTW_FORWARD, FFTW_ESTIMATE);
fftw_execute(forwardPlan);
fftw_destroy_plan(forwardPlan);
// apply filter
index = 0;
for (int z = 0; z < zRes; z++)
for (int y = 0; y < yRes; y++)
for (int x = 0; x < xRes; x++, index++)
{
backward[index][0] *= filter[index];
backward[index][1] *= filter[index];
}
// backward FFT
fftw_plan backwardPlan = fftw_plan_dft_3d(xRes, yRes, zRes, backward, forward, FFTW_BACKWARD, FFTW_ESTIMATE);
fftw_execute(backwardPlan);
fftw_destroy_plan(backwardPlan);
// subtract out the low frequency components
index = 0;
for (int z = 0; z < zRes; z++)
for (int y = 0; y < yRes; y++)
for (int x = 0; x < xRes; x++, index++)
noise[index] -= forward[index][0] / totalCells;
// save out the noise tile
saveTile(noise, filename);
fftw_free(forward);
fftw_free(backward);
delete[] filter;
delete[] noise;
}
#endif
#endif /* FFT_NOISE_H_ */
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