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/*
* Copyright 2011-2013 Blender Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef __BSDF_OREN_NAYAR_H__
#define __BSDF_OREN_NAYAR_H__
CCL_NAMESPACE_BEGIN
typedef ccl_addr_space struct OrenNayarBsdf {
SHADER_CLOSURE_BASE;
float roughness;
float a;
float b;
} OrenNayarBsdf;
static_assert(sizeof(ShaderClosure) >= sizeof(OrenNayarBsdf), "OrenNayarBsdf is too large!");
ccl_device float3 bsdf_oren_nayar_get_intensity(const ShaderClosure *sc,
float3 n,
float3 v,
float3 l)
{
const OrenNayarBsdf *bsdf = (const OrenNayarBsdf *)sc;
float nl = max(dot(n, l), 0.0f);
float nv = max(dot(n, v), 0.0f);
float t = dot(l, v) - nl * nv;
if (t > 0.0f)
t /= max(nl, nv) + FLT_MIN;
float is = nl * (bsdf->a + bsdf->b * t);
return make_float3(is, is, is);
}
ccl_device int bsdf_oren_nayar_setup(OrenNayarBsdf *bsdf)
{
float sigma = bsdf->roughness;
bsdf->type = CLOSURE_BSDF_OREN_NAYAR_ID;
sigma = saturate(sigma);
float div = 1.0f / (M_PI_F + ((3.0f * M_PI_F - 4.0f) / 6.0f) * sigma);
bsdf->a = 1.0f * div;
bsdf->b = sigma * div;
return SD_BSDF | SD_BSDF_HAS_EVAL;
}
ccl_device bool bsdf_oren_nayar_merge(const ShaderClosure *a, const ShaderClosure *b)
{
const OrenNayarBsdf *bsdf_a = (const OrenNayarBsdf *)a;
const OrenNayarBsdf *bsdf_b = (const OrenNayarBsdf *)b;
return (isequal_float3(bsdf_a->N, bsdf_b->N)) && (bsdf_a->roughness == bsdf_b->roughness);
}
ccl_device float3 bsdf_oren_nayar_eval_reflect(const ShaderClosure *sc,
const float3 I,
const float3 omega_in,
float *pdf)
{
const OrenNayarBsdf *bsdf = (const OrenNayarBsdf *)sc;
if (dot(bsdf->N, omega_in) > 0.0f) {
*pdf = 0.5f * M_1_PI_F;
return bsdf_oren_nayar_get_intensity(sc, bsdf->N, I, omega_in);
}
else {
*pdf = 0.0f;
return make_float3(0.0f, 0.0f, 0.0f);
}
}
ccl_device float3 bsdf_oren_nayar_eval_transmit(const ShaderClosure *sc,
const float3 I,
const float3 omega_in,
float *pdf)
{
return make_float3(0.0f, 0.0f, 0.0f);
}
ccl_device int bsdf_oren_nayar_sample(const ShaderClosure *sc,
float3 Ng,
float3 I,
float3 dIdx,
float3 dIdy,
float randu,
float randv,
float3 *eval,
float3 *omega_in,
float3 *domega_in_dx,
float3 *domega_in_dy,
float *pdf)
{
const OrenNayarBsdf *bsdf = (const OrenNayarBsdf *)sc;
sample_uniform_hemisphere(bsdf->N, randu, randv, omega_in, pdf);
if (dot(Ng, *omega_in) > 0.0f) {
*eval = bsdf_oren_nayar_get_intensity(sc, bsdf->N, I, *omega_in);
#ifdef __RAY_DIFFERENTIALS__
// TODO: find a better approximation for the bounce
*domega_in_dx = (2.0f * dot(bsdf->N, dIdx)) * bsdf->N - dIdx;
*domega_in_dy = (2.0f * dot(bsdf->N, dIdy)) * bsdf->N - dIdy;
#endif
}
else {
*pdf = 0.0f;
*eval = make_float3(0.0f, 0.0f, 0.0f);
}
return LABEL_REFLECT | LABEL_DIFFUSE;
}
CCL_NAMESPACE_END
#endif /* __BSDF_OREN_NAYAR_H__ */
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