Blender  V3.3
bsdf_ashikhmin_velvet.h
Go to the documentation of this file.
1 /* SPDX-License-Identifier: BSD-3-Clause
2  *
3  * Adapted from Open Shading Language
4  * Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
5  * All Rights Reserved.
6  *
7  * Modifications Copyright 2011-2022 Blender Foundation. */
8 
9 #pragma once
10 
11 #include "kernel/sample/mapping.h"
12 
14 
15 typedef struct VelvetBsdf {
17 
18  float sigma;
19  float invsigma2;
21 
22 static_assert(sizeof(ShaderClosure) >= sizeof(VelvetBsdf), "VelvetBsdf is too large!");
23 
25 {
26  float sigma = fmaxf(bsdf->sigma, 0.01f);
27  bsdf->invsigma2 = 1.0f / (sigma * sigma);
28 
30 
31  return SD_BSDF | SD_BSDF_HAS_EVAL;
32 }
33 
35  const float3 I,
36  const float3 omega_in,
37  ccl_private float *pdf)
38 {
39  ccl_private const VelvetBsdf *bsdf = (ccl_private const VelvetBsdf *)sc;
40  float m_invsigma2 = bsdf->invsigma2;
41  float3 N = bsdf->N;
42 
43  float cosNO = dot(N, I);
44  float cosNI = dot(N, omega_in);
45  if (cosNO > 0 && cosNI > 0) {
46  float3 H = normalize(omega_in + I);
47 
48  float cosNH = dot(N, H);
49  float cosHO = fabsf(dot(I, H));
50 
51  if (!(fabsf(cosNH) < 1.0f - 1e-5f && cosHO > 1e-5f)) {
52  *pdf = 0.0f;
53  return make_float3(0.0f, 0.0f, 0.0f);
54  }
55  float cosNHdivHO = cosNH / cosHO;
56  cosNHdivHO = fmaxf(cosNHdivHO, 1e-5f);
57 
58  float fac1 = 2 * fabsf(cosNHdivHO * cosNO);
59  float fac2 = 2 * fabsf(cosNHdivHO * cosNI);
60 
61  float sinNH2 = 1 - cosNH * cosNH;
62  float sinNH4 = sinNH2 * sinNH2;
63  float cotangent2 = (cosNH * cosNH) / sinNH2;
64 
65  float D = expf(-cotangent2 * m_invsigma2) * m_invsigma2 * M_1_PI_F / sinNH4;
66  float G = fminf(1.0f, fminf(fac1, fac2)); // TODO: derive G from D analytically
67 
68  float out = 0.25f * (D * G) / cosNO;
69 
70  *pdf = 0.5f * M_1_PI_F;
71  return make_float3(out, out, out);
72  }
73 
74  *pdf = 0.0f;
75  return make_float3(0.0f, 0.0f, 0.0f);
76 }
77 
79  const float3 I,
80  const float3 omega_in,
81  ccl_private float *pdf)
82 {
83  *pdf = 0.0f;
84  return make_float3(0.0f, 0.0f, 0.0f);
85 }
86 
88  float3 Ng,
89  float3 I,
90  float3 dIdx,
91  float3 dIdy,
92  float randu,
93  float randv,
94  ccl_private float3 *eval,
95  ccl_private float3 *omega_in,
96  ccl_private float3 *domega_in_dx,
97  ccl_private float3 *domega_in_dy,
98  ccl_private float *pdf)
99 {
100  ccl_private const VelvetBsdf *bsdf = (ccl_private const VelvetBsdf *)sc;
101  float m_invsigma2 = bsdf->invsigma2;
102  float3 N = bsdf->N;
103 
104  // we are viewing the surface from above - send a ray out with uniform
105  // distribution over the hemisphere
106  sample_uniform_hemisphere(N, randu, randv, omega_in, pdf);
107 
108  if (dot(Ng, *omega_in) > 0) {
109  float3 H = normalize(*omega_in + I);
110 
111  float cosNI = dot(N, *omega_in);
112  float cosNO = dot(N, I);
113  float cosNH = dot(N, H);
114  float cosHO = fabsf(dot(I, H));
115 
116  if (fabsf(cosNO) > 1e-5f && fabsf(cosNH) < 1.0f - 1e-5f && cosHO > 1e-5f) {
117  float cosNHdivHO = cosNH / cosHO;
118  cosNHdivHO = fmaxf(cosNHdivHO, 1e-5f);
119 
120  float fac1 = 2 * fabsf(cosNHdivHO * cosNO);
121  float fac2 = 2 * fabsf(cosNHdivHO * cosNI);
122 
123  float sinNH2 = 1 - cosNH * cosNH;
124  float sinNH4 = sinNH2 * sinNH2;
125  float cotangent2 = (cosNH * cosNH) / sinNH2;
126 
127  float D = expf(-cotangent2 * m_invsigma2) * m_invsigma2 * M_1_PI_F / sinNH4;
128  float G = fminf(1.0f, fminf(fac1, fac2)); // TODO: derive G from D analytically
129 
130  float power = 0.25f * (D * G) / cosNO;
131 
132  *eval = make_float3(power, power, power);
133 
134 #ifdef __RAY_DIFFERENTIALS__
135  // TODO: find a better approximation for the retroreflective bounce
136  *domega_in_dx = (2 * dot(N, dIdx)) * N - dIdx;
137  *domega_in_dy = (2 * dot(N, dIdy)) * N - dIdy;
138 #endif
139  }
140  else {
141  *pdf = 0.0f;
142  *eval = make_float3(0.0f, 0.0f, 0.0f);
143  }
144  }
145  else {
146  *pdf = 0.0f;
147  *eval = make_float3(0.0f, 0.0f, 0.0f);
148  }
149  return LABEL_REFLECT | LABEL_DIFFUSE;
150 }
151 
ccl_device int bsdf_ashikhmin_velvet_setup(ccl_private VelvetBsdf *bsdf)
ccl_device int bsdf_ashikhmin_velvet_sample(ccl_private const ShaderClosure *sc, float3 Ng, float3 I, float3 dIdx, float3 dIdy, float randu, float randv, ccl_private float3 *eval, ccl_private float3 *omega_in, ccl_private float3 *domega_in_dx, ccl_private float3 *domega_in_dy, ccl_private float *pdf)
CCL_NAMESPACE_BEGIN struct VelvetBsdf VelvetBsdf
ccl_device float3 bsdf_ashikhmin_velvet_eval_transmit(ccl_private const ShaderClosure *sc, const float3 I, const float3 omega_in, ccl_private float *pdf)
ccl_device float3 bsdf_ashikhmin_velvet_eval_reflect(ccl_private const ShaderClosure *sc, const float3 I, const float3 omega_in, ccl_private float *pdf)
#define ccl_device
Definition: cuda/compat.h:32
#define expf(x)
Definition: cuda/compat.h:106
#define ccl_private
Definition: cuda/compat.h:48
#define CCL_NAMESPACE_END
Definition: cuda/compat.h:9
@ CLOSURE_BSDF_ASHIKHMIN_VELVET_ID
@ SD_BSDF_HAS_EVAL
Definition: kernel/types.h:744
@ SD_BSDF
Definition: kernel/types.h:742
@ LABEL_DIFFUSE
Definition: kernel/types.h:319
@ LABEL_REFLECT
Definition: kernel/types.h:318
ShaderClosure
Definition: kernel/types.h:726
#define N
#define G(x, y, z)
#define H(x, y, z)
#define fmaxf(x, y)
Definition: metal/compat.h:228
#define fminf(x, y)
Definition: metal/compat.h:229
#define fabsf(x)
Definition: metal/compat.h:219
#define make_float3(x, y, z)
Definition: metal/compat.h:204
T dot(const vec_base< T, Size > &a, const vec_base< T, Size > &b)
vec_base< T, Size > normalize(const vec_base< T, Size > &v)
static const pxr::TfToken out("out", pxr::TfToken::Immortal)
#define I
ccl_device_inline void sample_uniform_hemisphere(const float3 N, float randu, float randv, ccl_private float3 *omega_in, ccl_private float *pdf)
#define M_1_PI_F
Definition: util/math.h:43
BLI_INLINE float D(const float *data, const int res[3], int x, int y, int z)
Definition: voxel.c:13