1
2 //
3 // This source file is part of appleseed.
4 // Visit https://appleseedhq.net/ for additional information and resources.
5 //
6 // This software is released under the MIT license.
7 //
8 // Copyright (c) 2010-2013 Francois Beaune, Jupiter Jazz Limited
9 // Copyright (c) 2014-2018 Francois Beaune, The appleseedhq Organization
10 //
11 // Permission is hereby granted, free of charge, to any person obtaining a copy
12 // of this software and associated documentation files (the "Software"), to deal
13 // in the Software without restriction, including without limitation the rights
14 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
15 // copies of the Software, and to permit persons to whom the Software is
16 // furnished to do so, subject to the following conditions:
17 //
18 // The above copyright notice and this permission notice shall be included in
19 // all copies or substantial portions of the Software.
20 //
21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
22 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
23 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
24 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
25 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
26 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
27 // THE SOFTWARE.
28 //
29
30 #pragma once
31
32 // appleseed.foundation headers.
33 #include "foundation/core/concepts/noncopyable.h"
34 #include "foundation/math/vector.h"
35 #include "foundation/platform/compiler.h"
36
37 // Standard headers.
38 #include <cstddef>
39 #include <vector>
40
41 namespace renderer
42 {
43
44 //
45 // A strictly deterministic pixel sampler.
46 //
47 // Reference:
48 //
49 // Strictly Deterministic Sampling Methods in Computer Graphics
50 // http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.88.7937
51 //
52
53 class PixelSampler
54 : public foundation::NonCopyable
55 {
56 public:
57 // Initialize the pixel sampler for a given subpixel grid size.
58 void initialize(const size_t subpixel_grid_size);
59
60 // Compute the position of a pixel sample and optionally the initial instance
61 // number of the corresponding sampling context, given the integer coordinates
62 // of the subpixel grid cell containing the sample. The coordinates of the
63 // pixel sample are expressed in continous image space
64 // (https://github.com/appleseedhq/appleseed/wiki/Terminology).
65 void sample(
66 const int sx,
67 const int sy,
68 foundation::Vector2d& sample_position) const;
69 void sample(
70 const int sx,
71 const int sy,
72 foundation::Vector2d& sample_position,
73 size_t& initial_instance) const;
74
75 private:
76 size_t m_subpixel_grid_size;
77 double m_rcp_subpixel_grid_size; // 1.0 / subpixel_grid_size
78 double m_rcp_period; // 1.0 / m_period
79 size_t m_log_period; // log2(m_period)
80 size_t m_period; // m_sigma.size()
81 size_t m_period_mask; // m_period - 1
82 std::vector<size_t> m_sigma; // 2^N * radical_inverse_base2(0..N-1)
83 };
84
85
86 //
87 // PixelSampler class implementation.
88 //
89
sample(const int sx,const int sy,foundation::Vector2d & sample_position)90 APPLESEED_FORCE_INLINE void PixelSampler::sample(
91 const int sx,
92 const int sy,
93 foundation::Vector2d& sample_position) const
94 {
95 // Compute the sample coordinates in image space.
96 if (m_subpixel_grid_size == 1)
97 {
98 sample_position[0] = sx + 0.5;
99 sample_position[1] = sy + 0.5;
100 }
101 else
102 {
103 const size_t j = sx & m_period_mask;
104 const size_t k = sy & m_period_mask;
105 const size_t sigma_j = m_sigma[j];
106 const size_t sigma_k = m_sigma[k];
107
108 sample_position[0] = (sx + sigma_k * m_rcp_period) * m_rcp_subpixel_grid_size;
109 sample_position[1] = (sy + sigma_j * m_rcp_period) * m_rcp_subpixel_grid_size;
110 }
111 }
112
sample(const int sx,const int sy,foundation::Vector2d & sample_position,size_t & initial_instance)113 APPLESEED_FORCE_INLINE void PixelSampler::sample(
114 const int sx,
115 const int sy,
116 foundation::Vector2d& sample_position,
117 size_t& initial_instance) const
118 {
119 const size_t j = sx & m_period_mask;
120 const size_t k = sy & m_period_mask;
121 const size_t sigma_k = m_sigma[k];
122
123 // Compute the initial instance number of the sampling context.
124 initial_instance = (j << m_log_period) + sigma_k;
125
126 // Compute the sample coordinates in image space.
127 if (m_subpixel_grid_size == 1)
128 {
129 sample_position[0] = sx + 0.5;
130 sample_position[1] = sy + 0.5;
131 }
132 else
133 {
134 const size_t sigma_j = m_sigma[j];
135
136 sample_position[0] = (sx + sigma_k * m_rcp_period) * m_rcp_subpixel_grid_size;
137 sample_position[1] = (sy + sigma_j * m_rcp_period) * m_rcp_subpixel_grid_size;
138 }
139 }
140
141 } // namespace renderer
142