forked from bartvdbraak/blender
9d50175b6c
There were two cases where correlation issues were obvious: - File from T38710 was giving issues in 2.78a again - File from T50116 was having totally different shadow between sample 1 and sample 32. Use some more simplified version of CMJ hash which seems to give nice randomized value which solves the correlation. This commit will break all unit test files, but it's a bug fix so perhaps OK to commit this. This also fixes T41143: Sobol gives nonuniform noise Proper science paper about hash function is coming. Reviewers: brecht Reviewed By: brecht Subscribers: lukasstockner97 Differential Revision: https://developer.blender.org/D2385
219 lines
4.3 KiB
C
219 lines
4.3 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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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 > 1) && ((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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/* 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(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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#elif defined(__KERNEL_CUDA__)
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return a >> (__ffs(b) - 1);
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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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#elif defined(__KERNEL_CUDA__)
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return ((1 << (32 - __clz(w))) - 1);
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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 uint cmj_hash_simple(uint i, uint p)
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{
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i = (i ^ 61) ^ p;
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i += i << 3;
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i ^= i >> 4;
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i *= 0x27d4eb2d;
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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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#if defined(__KERNEL_CUDA__)
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int m = float_to_int(__fsqrt_ru(N));
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#else
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int m = float_to_int(sqrtf(N));
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#endif
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int n = (N - 1)/m + 1;
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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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/* Doing s*inmv gives precision issues here. */
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sdivm = s / m;
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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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