blob: 511419fca9c21df7d9fb858eaa8244443366fd14 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
|
/* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 2008, Frances Y. Kuo and Stephen Joe
* All rights reserved. */
/*
* Sobol sequence direction vectors.
*
* This file contains code to create direction vectors for generating sobol
* sequences in high dimensions. It is adapted from code on this webpage:
*
* http://web.maths.unsw.edu.au/~fkuo/sobol/
*
* From these papers:
*
* S. Joe and F. Y. Kuo, Remark on Algorithm 659: Implementing Sobol's quasirandom
* sequence generator, ACM Trans. Math. Softw. 29, 49-57 (2003)
*
* S. Joe and F. Y. Kuo, Constructing Sobol sequences with better two-dimensional
* projections, SIAM J. Sci. Comput. 30, 2635-2654 (2008)
*/
#include "util/types.h"
#include "scene/sobol.h"
CCL_NAMESPACE_BEGIN
#include "scene/sobol.tables"
void sobol_generate_direction_vectors(uint vectors[][SOBOL_BITS], int dimensions)
{
assert(dimensions <= SOBOL_MAX_DIMENSIONS);
const uint L = SOBOL_BITS;
/* first dimension is exception */
uint *v = vectors[0];
for (uint i = 0; i < L; i++)
v[i] = 1 << (31 - i); // all m's = 1
for (int dim = 1; dim < dimensions; dim++) {
const SobolDirectionNumbers *numbers = &SOBOL_NUMBERS[dim - 1];
const uint s = numbers->s;
const uint a = numbers->a;
const uint *m = numbers->m;
v = vectors[dim];
if (L <= s) {
for (uint i = 0; i < L; i++)
v[i] = m[i] << (31 - i);
}
else {
for (uint i = 0; i < s; i++)
v[i] = m[i] << (31 - i);
for (uint i = s; i < L; i++) {
v[i] = v[i - s] ^ (v[i - s] >> s);
for (uint k = 1; k < s; k++)
v[i] ^= (((a >> (s - 1 - k)) & 1) * v[i - k]);
}
}
}
}
CCL_NAMESPACE_END
|
