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/*
* Copyright 2011-2017 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_PRINCIPLED_DIFFUSE_H__
#define __BSDF_PRINCIPLED_DIFFUSE_H__
/* DISNEY PRINCIPLED DIFFUSE BRDF
*
* Shading model by Brent Burley (Disney): "Physically Based Shading at Disney" (2012)
*/
CCL_NAMESPACE_BEGIN
typedef ccl_addr_space struct PrincipledDiffuseBsdf {
SHADER_CLOSURE_BASE;
float roughness;
} PrincipledDiffuseBsdf;
static_assert(sizeof(ShaderClosure) >= sizeof(PrincipledDiffuseBsdf),
"PrincipledDiffuseBsdf is too large!");
ccl_device float3 calculate_principled_diffuse_brdf(
const PrincipledDiffuseBsdf *bsdf, float3 N, float3 V, float3 L, float3 H, float *pdf)
{
float NdotL = dot(N, L);
float NdotV = dot(N, V);
if (NdotL <= 0 || NdotV <= 0) {
*pdf = 0.0f;
return make_float3(0.0f, 0.0f, 0.0f);
}
float LdotH = dot(L, H);
float FL = schlick_fresnel(NdotL), FV = schlick_fresnel(NdotV);
const float Fd90 = 0.5f + 2.0f * LdotH * LdotH * bsdf->roughness;
float Fd = (1.0f * (1.0f - FL) + Fd90 * FL) * (1.0f * (1.0f - FV) + Fd90 * FV);
float value = M_1_PI_F * NdotL * Fd;
return make_float3(value, value, value);
}
ccl_device int bsdf_principled_diffuse_setup(PrincipledDiffuseBsdf *bsdf)
{
bsdf->type = CLOSURE_BSDF_PRINCIPLED_DIFFUSE_ID;
return SD_BSDF | SD_BSDF_HAS_EVAL;
}
ccl_device bool bsdf_principled_diffuse_merge(const ShaderClosure *a, const ShaderClosure *b)
{
const PrincipledDiffuseBsdf *bsdf_a = (const PrincipledDiffuseBsdf *)a;
const PrincipledDiffuseBsdf *bsdf_b = (const PrincipledDiffuseBsdf *)b;
return (isequal_float3(bsdf_a->N, bsdf_b->N) && bsdf_a->roughness == bsdf_b->roughness);
}
ccl_device float3 bsdf_principled_diffuse_eval_reflect(const ShaderClosure *sc,
const float3 I,
const float3 omega_in,
float *pdf)
{
const PrincipledDiffuseBsdf *bsdf = (const PrincipledDiffuseBsdf *)sc;
float3 N = bsdf->N;
float3 V = I; // outgoing
float3 L = omega_in; // incoming
float3 H = normalize(L + V);
if (dot(N, omega_in) > 0.0f) {
*pdf = fmaxf(dot(N, omega_in), 0.0f) * M_1_PI_F;
return calculate_principled_diffuse_brdf(bsdf, N, V, L, H, pdf);
}
else {
*pdf = 0.0f;
return make_float3(0.0f, 0.0f, 0.0f);
}
}
ccl_device float3 bsdf_principled_diffuse_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_principled_diffuse_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 PrincipledDiffuseBsdf *bsdf = (const PrincipledDiffuseBsdf *)sc;
float3 N = bsdf->N;
sample_cos_hemisphere(N, randu, randv, omega_in, pdf);
if (dot(Ng, *omega_in) > 0) {
float3 H = normalize(I + *omega_in);
*eval = calculate_principled_diffuse_brdf(bsdf, N, I, *omega_in, H, pdf);
#ifdef __RAY_DIFFERENTIALS__
// TODO: find a better approximation for the diffuse bounce
*domega_in_dx = -((2 * dot(N, dIdx)) * N - dIdx);
*domega_in_dy = -((2 * dot(N, dIdy)) * N - dIdy);
#endif
}
else {
*pdf = 0.0f;
}
return LABEL_REFLECT | LABEL_DIFFUSE;
}
CCL_NAMESPACE_END
#endif /* __BSDF_PRINCIPLED_DIFFUSE_H__ */
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