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/*
* Copyright 2011, Blender Foundation.
*
* This program 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 2
* of the License, or (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
CCL_NAMESPACE_BEGIN
typedef uint RNG;
#ifdef __SOBOL__
/* High Dimensional Sobol */
/* van der corput radical inverse */
__device uint van_der_corput(uint bits)
{
bits = (bits << 16) | (bits >> 16);
bits = ((bits & 0x00ff00ff) << 8) | ((bits & 0xff00ff00) >> 8);
bits = ((bits & 0x0f0f0f0f) << 4) | ((bits & 0xf0f0f0f0) >> 4);
bits = ((bits & 0x33333333) << 2) | ((bits & 0xcccccccc) >> 2);
bits = ((bits & 0x55555555) << 1) | ((bits & 0xaaaaaaaa) >> 1);
return bits;
}
/* sobol radical inverse */
__device uint sobol(uint i)
{
uint r = 0;
for(uint v = 1U << 31; i; i >>= 1, v ^= v >> 1)
if(i & 1)
r ^= v;
return r;
}
/* inverse of sobol radical inverse */
__device uint sobol_inverse(uint i)
{
const uint msb = 1U << 31;
uint r = 0;
for(uint v = 1; i; i <<= 1, v ^= v << 1)
if(i & msb)
r ^= v;
return r;
}
/* multidimensional sobol with generator matrices
dimension 0 and 1 are equal to van_der_corput() and sobol() respectively */
__device uint sobol_dimension(KernelGlobals *kg, int index, int dimension)
{
uint result = 0;
uint i = index;
for(uint j = 0; i; i >>= 1, j++)
if(i & 1)
result ^= kernel_tex_fetch(__sobol_directions, 32*dimension + j);
return result;
}
/* lookup index and x/y coordinate, assumes m is a power of two */
__device uint sobol_lookup(const uint m, const uint frame, const uint ex, const uint ey, uint *x, uint *y)
{
/* shift is constant per frame */
const uint shift = frame << (m << 1);
const uint sobol_shift = sobol(shift);
/* van der Corput is its own inverse */
const uint lower = van_der_corput(ex << (32 - m));
/* need to compensate for ey difference and shift */
const uint sobol_lower = sobol(lower);
const uint mask = ~-(1 << m) << (32 - m); /* only m upper bits */
const uint delta = ((ey << (32 - m)) ^ sobol_lower ^ sobol_shift) & mask;
/* only use m upper bits for the index (m is a power of two) */
const uint sobol_result = delta | (delta >> m);
const uint upper = sobol_inverse(sobol_result);
const uint index = shift | upper | lower;
*x = van_der_corput(index);
*y = sobol_shift ^ sobol_result ^ sobol_lower;
return index;
}
__device_inline float path_rng(KernelGlobals *kg, RNG *rng, int sample, int dimension)
{
#ifdef __SOBOL_FULL_SCREEN__
uint result = sobol_dimension(kg, *rng, dimension);
float r = (float)result * (1.0f/(float)0xFFFFFFFF);
return r;
#else
/* compute sobol sequence value using direction vectors */
uint result = sobol_dimension(kg, sample, dimension);
float r = (float)result * (1.0f/(float)0xFFFFFFFF);
/* Cranly-Patterson rotation using rng seed */
float shift;
if(dimension & 1)
shift = (*rng >> 16)/((float)0xFFFF);
else
shift = (*rng & 0xFFFF)/((float)0xFFFF);
return r + shift - floor(r + shift);
#endif
}
__device_inline void path_rng_init(KernelGlobals *kg, __global uint *rng_state, int sample, RNG *rng, int x, int y, float *fx, float *fy)
{
#ifdef __SOBOL_FULL_SCREEN__
uint px, py;
uint bits = 16; /* limits us to 65536x65536 and 65536 samples */
uint size = 1 << bits;
uint frame = sample;
*rng = sobol_lookup(bits, frame, x, y, &px, &py);
*fx = size * (float)px * (1.0f/(float)0xFFFFFFFF) - x;
*fy = size * (float)py * (1.0f/(float)0xFFFFFFFF) - y;
#else
*rng = rng_state[x + y*kernel_data.cam.width];
*fx = path_rng(kg, rng, sample, PRNG_FILTER_U);
*fy = path_rng(kg, rng, sample, PRNG_FILTER_V);
#endif
}
__device void path_rng_end(KernelGlobals *kg, __global uint *rng_state, RNG rng, int x, int y)
{
/* nothing to do */
}
#else
/* Linear Congruential Generator */
__device float path_rng(KernelGlobals *kg, RNG *rng, int sample, int dimension)
{
/* implicit mod 2^32 */
*rng = (1103515245*(*rng) + 12345);
return (float)*rng * (1.0f/(float)0xFFFFFFFF);
}
__device void path_rng_init(KernelGlobals *kg, __global uint *rng_state, int sample, RNG *rng, int x, int y, float *fx, float *fy)
{
/* load state */
*rng = rng_state[x + y*kernel_data.cam.width];
*fx = path_rng(kg, rng, sample, PRNG_FILTER_U);
*fy = path_rng(kg, rng, sample, PRNG_FILTER_V);
}
__device void path_rng_end(KernelGlobals *kg, __global uint *rng_state, RNG rng, int x, int y)
{
/* store state for next sample */
rng_state[x + y*kernel_data.cam.width] = rng;
}
#endif
CCL_NAMESPACE_END
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