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/* SPDX-License-Identifier: Apache-2.0
* Copyright 2011-2022 Blender Foundation */
#pragma once
CCL_NAMESPACE_BEGIN
typedef struct OrenNayarBsdf {
SHADER_CLOSURE_BASE;
float roughness;
float a;
float b;
} OrenNayarBsdf;
static_assert(sizeof(ShaderClosure) >= sizeof(OrenNayarBsdf), "OrenNayarBsdf is too large!");
ccl_device Spectrum bsdf_oren_nayar_get_intensity(ccl_private const ShaderClosure *sc,
float3 n,
float3 v,
float3 l)
{
ccl_private const OrenNayarBsdf *bsdf = (ccl_private 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_spectrum(is);
}
ccl_device int bsdf_oren_nayar_setup(ccl_private OrenNayarBsdf *bsdf)
{
float sigma = bsdf->roughness;
bsdf->type = CLOSURE_BSDF_OREN_NAYAR_ID;
sigma = saturatef(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 Spectrum bsdf_oren_nayar_eval_reflect(ccl_private const ShaderClosure *sc,
const float3 I,
const float3 omega_in,
ccl_private float *pdf)
{
ccl_private const OrenNayarBsdf *bsdf = (ccl_private 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 zero_spectrum();
}
}
ccl_device Spectrum bsdf_oren_nayar_eval_transmit(ccl_private const ShaderClosure *sc,
const float3 I,
const float3 omega_in,
ccl_private float *pdf)
{
*pdf = 0.0f;
return zero_spectrum();
}
ccl_device int bsdf_oren_nayar_sample(ccl_private const ShaderClosure *sc,
float3 Ng,
float3 I,
float randu,
float randv,
ccl_private Spectrum *eval,
ccl_private float3 *omega_in,
ccl_private float *pdf)
{
ccl_private const OrenNayarBsdf *bsdf = (ccl_private 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);
}
else {
*pdf = 0.0f;
*eval = zero_spectrum();
}
return LABEL_REFLECT | LABEL_DIFFUSE;
}
CCL_NAMESPACE_END
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