205 lines
4.0 KiB
C
205 lines
4.0 KiB
C
/*
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* Copyright 2011-2013 Blender Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License
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*/
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/* TODO(sergey): Consider moving portable ctz/clz stuff to util. */
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#ifdef _MSC_VER
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# include <intrin.h>
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#endif
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CCL_NAMESPACE_BEGIN
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/* "Correlated Multi-Jittered Sampling"
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* Andrew Kensler, Pixar Technical Memo 13-01, 2013 */
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/* todo: find good value, suggested 64 gives pattern on cornell box ceiling */
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#define CMJ_RANDOM_OFFSET_LIMIT 4096
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ccl_device_inline bool cmj_is_pow2(int i)
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{
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return (i & (i - 1)) == 0;
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}
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ccl_device_inline int cmj_fast_mod_pow2(int a, int b)
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{
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return (a & (b - 1));
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}
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/* a must be > 0 and b must be > 1 */
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ccl_device_inline int cmj_fast_div_pow2(int a, int b)
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{
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kernel_assert(a > 0);
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kernel_assert(b > 1);
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#if defined(__KERNEL_SSE2__)
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# ifdef _MSC_VER
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unsigned long ctz;
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_BitScanForward(&ctz, b);
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return a >> ctz;
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# else
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return a >> __builtin_ctz(b);
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# endif
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#else
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return a/b;
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#endif
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}
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ccl_device_inline uint cmj_w_mask(uint w)
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{
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kernel_assert(w > 1);
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#if defined(__KERNEL_SSE2__)
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# ifdef _MSC_VER
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unsigned long leading_zero;
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_BitScanReverse(&leading_zero, w);
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return ((1 << (1 + leading_zero)) - 1);
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# else
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return ((1 << (32 - __builtin_clz(w))) - 1);
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# endif
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#else
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w |= w >> 1;
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w |= w >> 2;
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w |= w >> 4;
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w |= w >> 8;
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w |= w >> 16;
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return w;
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#endif
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}
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ccl_device_inline uint cmj_permute(uint i, uint l, uint p)
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{
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uint w = l - 1;
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if((l & w) == 0) {
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/* l is a power of two (fast) */
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i ^= p;
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i *= 0xe170893d;
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i ^= p >> 16;
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i ^= (i & w) >> 4;
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i ^= p >> 8;
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i *= 0x0929eb3f;
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i ^= p >> 23;
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i ^= (i & w) >> 1;
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i *= 1 | p >> 27;
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i *= 0x6935fa69;
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i ^= (i & w) >> 11;
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i *= 0x74dcb303;
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i ^= (i & w) >> 2;
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i *= 0x9e501cc3;
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i ^= (i & w) >> 2;
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i *= 0xc860a3df;
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i &= w;
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i ^= i >> 5;
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return (i + p) & w;
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}
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else {
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/* l is not a power of two (slow) */
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w = cmj_w_mask(w);
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do {
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i ^= p;
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i *= 0xe170893d;
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i ^= p >> 16;
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i ^= (i & w) >> 4;
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i ^= p >> 8;
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i *= 0x0929eb3f;
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i ^= p >> 23;
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i ^= (i & w) >> 1;
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i *= 1 | p >> 27;
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i *= 0x6935fa69;
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i ^= (i & w) >> 11;
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i *= 0x74dcb303;
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i ^= (i & w) >> 2;
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i *= 0x9e501cc3;
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i ^= (i & w) >> 2;
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i *= 0xc860a3df;
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i &= w;
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i ^= i >> 5;
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} while (i >= l);
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return (i + p) % l;
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}
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}
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ccl_device_inline uint cmj_hash(uint i, uint p)
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{
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i ^= p;
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i ^= i >> 17;
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i ^= i >> 10;
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i *= 0xb36534e5;
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i ^= i >> 12;
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i ^= i >> 21;
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i *= 0x93fc4795;
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i ^= 0xdf6e307f;
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i ^= i >> 17;
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i *= 1 | p >> 18;
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return i;
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}
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ccl_device_inline float cmj_randfloat(uint i, uint p)
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{
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return cmj_hash(i, p) * (1.0f / 4294967808.0f);
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}
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#ifdef __CMJ__
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ccl_device float cmj_sample_1D(int s, int N, int p)
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{
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kernel_assert(s < N);
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uint x = cmj_permute(s, N, p * 0x68bc21eb);
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float jx = cmj_randfloat(s, p * 0x967a889b);
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float invN = 1.0f/N;
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return (x + jx)*invN;
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}
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ccl_device void cmj_sample_2D(int s, int N, int p, float *fx, float *fy)
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{
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kernel_assert(s < N);
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int m = float_to_int(sqrtf(N));
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int n = (N + m - 1)/m;
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float invN = 1.0f/N;
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float invm = 1.0f/m;
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float invn = 1.0f/n;
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s = cmj_permute(s, N, p * 0x51633e2d);
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int sdivm, smodm;
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if(cmj_is_pow2(m)) {
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sdivm = cmj_fast_div_pow2(s, m);
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smodm = cmj_fast_mod_pow2(s, m);
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}
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else {
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sdivm = float_to_int(s * invm);
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smodm = s - sdivm*m;
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}
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uint sx = cmj_permute(smodm, m, p * 0x68bc21eb);
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uint sy = cmj_permute(sdivm, n, p * 0x02e5be93);
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float jx = cmj_randfloat(s, p * 0x967a889b);
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float jy = cmj_randfloat(s, p * 0x368cc8b7);
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*fx = (sx + (sy + jx)*invn)*invm;
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*fy = (s + jy)*invN;
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}
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#endif
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CCL_NAMESPACE_END
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