blob: 928cd6a19320b5a8f4275894e5ce261fa1f72b67 (
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
|
/* SPDX-License-Identifier: Apache-2.0
* Copyright 2011-2022 Blender Foundation */
#include "util/math_cdf.h"
#include "util/algorithm.h"
#include "util/math.h"
CCL_NAMESPACE_BEGIN
/* Invert pre-calculated CDF function. */
void util_cdf_invert(const int resolution,
const float from,
const float to,
const vector<float> &cdf,
const bool make_symmetric,
vector<float> &inv_cdf)
{
const float inv_resolution = 1.0f / (float)resolution;
const float range = to - from;
inv_cdf.resize(resolution);
if (make_symmetric) {
const int half_size = (resolution - 1) / 2;
for (int i = 0; i <= half_size; i++) {
float x = i / (float)half_size;
int index = upper_bound(cdf.begin(), cdf.end(), x) - cdf.begin();
float t;
if (index < cdf.size() - 1) {
t = (x - cdf[index]) / (cdf[index + 1] - cdf[index]);
}
else {
t = 0.0f;
index = cdf.size() - 1;
}
float y = ((index + t) / (resolution - 1)) * (2.0f * range);
inv_cdf[half_size + i] = 0.5f * (1.0f + y);
inv_cdf[half_size - i] = 0.5f * (1.0f - y);
}
}
else {
for (int i = 0; i < resolution; i++) {
float x = from + range * (float)i * inv_resolution;
int index = upper_bound(cdf.begin(), cdf.end(), x) - cdf.begin();
float t;
if (index < cdf.size() - 1) {
t = (x - cdf[index]) / (cdf[index + 1] - cdf[index]);
}
else {
t = 0.0f;
index = resolution;
}
inv_cdf[i] = (index + t) * inv_resolution;
}
}
}
CCL_NAMESPACE_END
|
