forked from bartvdbraak/blender
902209eda5
Similar to the Microfacet Closures, the Principled BSDF Sheen closure is added at a high weight but typically results in fairly low values. Therefore, the default weight is a bad indicator of importance. The fix here is the same as it was back then for Microfacets: Compute an average weight using the normal as the half-vector and use it to scale down the sample weight and the albedo channel. In addition to drastically improving denoising of materials with sheen when using the new Denoising node, this also can reduce noise on such materials considerably.
142 lines
4.4 KiB
C
142 lines
4.4 KiB
C
/*
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* Copyright 2011-2017 Blender Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef __BSDF_PRINCIPLED_SHEEN_H__
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#define __BSDF_PRINCIPLED_SHEEN_H__
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/* DISNEY PRINCIPLED SHEEN BRDF
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*
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* Shading model by Brent Burley (Disney): "Physically Based Shading at Disney" (2012)
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*/
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CCL_NAMESPACE_BEGIN
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typedef ccl_addr_space struct PrincipledSheenBsdf {
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SHADER_CLOSURE_BASE;
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float avg_value;
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} PrincipledSheenBsdf;
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static_assert(sizeof(ShaderClosure) >= sizeof(PrincipledSheenBsdf),
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"PrincipledSheenBsdf is too large!");
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ccl_device_inline float calculate_avg_principled_sheen_brdf(float3 N, float3 I)
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{
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/* To compute the average, we set the half-vector to the normal, resulting in
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* NdotI = NdotL = NdotV = LdotH */
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float NdotI = dot(N, I);
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if (NdotI < 0.0f) {
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return 0.0f;
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}
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return schlick_fresnel(NdotI) * NdotI;
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}
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ccl_device float3
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calculate_principled_sheen_brdf(float3 N, float3 V, float3 L, float3 H, float *pdf)
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{
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float NdotL = dot(N, L);
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float NdotV = dot(N, V);
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if (NdotL < 0 || NdotV < 0) {
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*pdf = 0.0f;
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return make_float3(0.0f, 0.0f, 0.0f);
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}
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float LdotH = dot(L, H);
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float value = schlick_fresnel(LdotH) * NdotL;
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return make_float3(value, value, value);
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}
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ccl_device int bsdf_principled_sheen_setup(const ShaderData *sd, PrincipledSheenBsdf *bsdf)
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{
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bsdf->type = CLOSURE_BSDF_PRINCIPLED_SHEEN_ID;
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bsdf->avg_value = calculate_avg_principled_sheen_brdf(bsdf->N, sd->I);
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bsdf->sample_weight *= bsdf->avg_value;
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return SD_BSDF | SD_BSDF_HAS_EVAL;
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}
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ccl_device float3 bsdf_principled_sheen_eval_reflect(const ShaderClosure *sc,
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const float3 I,
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const float3 omega_in,
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float *pdf)
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{
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const PrincipledSheenBsdf *bsdf = (const PrincipledSheenBsdf *)sc;
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float3 N = bsdf->N;
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float3 V = I; // outgoing
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float3 L = omega_in; // incoming
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float3 H = normalize(L + V);
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if (dot(N, omega_in) > 0.0f) {
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*pdf = fmaxf(dot(N, omega_in), 0.0f) * M_1_PI_F;
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return calculate_principled_sheen_brdf(N, V, L, H, pdf);
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}
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else {
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*pdf = 0.0f;
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return make_float3(0.0f, 0.0f, 0.0f);
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}
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}
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ccl_device float3 bsdf_principled_sheen_eval_transmit(const ShaderClosure *sc,
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const float3 I,
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const float3 omega_in,
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float *pdf)
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{
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return make_float3(0.0f, 0.0f, 0.0f);
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}
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ccl_device int bsdf_principled_sheen_sample(const ShaderClosure *sc,
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float3 Ng,
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float3 I,
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float3 dIdx,
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float3 dIdy,
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float randu,
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float randv,
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float3 *eval,
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float3 *omega_in,
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float3 *domega_in_dx,
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float3 *domega_in_dy,
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float *pdf)
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{
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const PrincipledSheenBsdf *bsdf = (const PrincipledSheenBsdf *)sc;
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float3 N = bsdf->N;
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sample_cos_hemisphere(N, randu, randv, omega_in, pdf);
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if (dot(Ng, *omega_in) > 0) {
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float3 H = normalize(I + *omega_in);
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*eval = calculate_principled_sheen_brdf(N, I, *omega_in, H, pdf);
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#ifdef __RAY_DIFFERENTIALS__
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// TODO: find a better approximation for the diffuse bounce
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*domega_in_dx = -((2 * dot(N, dIdx)) * N - dIdx);
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*domega_in_dy = -((2 * dot(N, dIdy)) * N - dIdy);
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#endif
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}
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else {
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*pdf = 0.0f;
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}
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return LABEL_REFLECT | LABEL_DIFFUSE;
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}
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CCL_NAMESPACE_END
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#endif /* __BSDF_PRINCIPLED_SHEEN_H__ */
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