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.renderer headers.
33 #include "renderer/global/globaltypes.h"
34
35 // appleseed.foundation headers.
36 #include "foundation/math/scalar.h"
37
38 // Standard headers.
39 #include <cassert>
40
41 namespace renderer
42 {
43
44 //
45 // Randomly cast a non-negative scalar n to an integer such that the expected value of that integer is n.
46 //
47
48 template <typename RNG, typename Int, typename Float>
stochastic_cast(RNG & rng,const Float n)49 inline Int stochastic_cast(RNG& rng, const Float n)
50 {
51 assert(n >= Float(0.0));
52
53 Int i = foundation::truncate<Int>(n);
54
55 const Float r = n - i;
56
57 if (r > Float(0.0))
58 {
59 if (foundation::rand2<Float>(rng) < n - i)
60 ++i;
61 }
62
63 return i;
64 }
65
66 template <typename Int, typename Float>
stochastic_cast(SamplingContext & sampling_context,const Float n)67 inline Int stochastic_cast(SamplingContext& sampling_context, const Float n)
68 {
69 assert(n >= Float(0.0));
70
71 Int i = foundation::truncate<Int>(n);
72
73 const Float r = n - i;
74
75 if (r > Float(0.0))
76 {
77 sampling_context.split_in_place(1, 1);
78
79 if (sampling_context.next2<Float>() < n - i)
80 ++i;
81 }
82
83 return i;
84 }
85
86 } // namespace renderer
87