d832d993c5
These replace float3 and packed_float3 in various places in the kernel where a spectral color representation will be used in the future. That representation will require more than 3 channels and conversion to from/RGB. The kernel code was refactored to remove the assumption that Spectrum and RGB colors are the same thing. There are no functional changes, Spectrum is still a float3 and the conversion functions are no-ops. Differential Revision: https://developer.blender.org/D15535
131 lines
4.0 KiB
C
131 lines
4.0 KiB
C
/* SPDX-License-Identifier: Apache-2.0
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* Copyright 2011-2022 Blender Foundation */
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#pragma once
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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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#include "kernel/closure/bsdf_util.h"
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CCL_NAMESPACE_BEGIN
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typedef 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 Spectrum
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calculate_principled_sheen_brdf(float3 N, float3 V, float3 L, float3 H, ccl_private 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 zero_spectrum();
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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_spectrum(value);
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}
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ccl_device int bsdf_principled_sheen_setup(ccl_private const ShaderData *sd,
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ccl_private 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 Spectrum bsdf_principled_sheen_eval_reflect(ccl_private const ShaderClosure *sc,
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const float3 I,
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const float3 omega_in,
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ccl_private float *pdf)
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{
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ccl_private const PrincipledSheenBsdf *bsdf = (ccl_private 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 zero_spectrum();
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}
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}
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ccl_device Spectrum bsdf_principled_sheen_eval_transmit(ccl_private const ShaderClosure *sc,
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const float3 I,
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const float3 omega_in,
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ccl_private float *pdf)
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{
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*pdf = 0.0f;
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return zero_spectrum();
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}
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ccl_device int bsdf_principled_sheen_sample(ccl_private 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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ccl_private Spectrum *eval,
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ccl_private float3 *omega_in,
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ccl_private float3 *domega_in_dx,
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ccl_private float3 *domega_in_dy,
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ccl_private float *pdf)
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{
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ccl_private const PrincipledSheenBsdf *bsdf = (ccl_private 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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*eval = zero_spectrum();
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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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