Weizhen Huang
543bf28fb1
wi is the viewing direction, and wo is the illumination direction. Under this notation, BSDF sampling always samples from wi and outputs wo, which is consistent with most of the papers and mitsuba. This order is reversed compared with PBRT, although PBRT also traces from the camera.
114 lines
3.4 KiB
C++
114 lines
3.4 KiB
C++
/* SPDX-License-Identifier: BSD-3-Clause
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*
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* Adapted from Open Shading Language
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* Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
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* All Rights Reserved.
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*
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* Modifications Copyright 2011-2022 Blender Foundation. */
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#pragma once
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#include "kernel/sample/mapping.h"
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CCL_NAMESPACE_BEGIN
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typedef struct DiffuseBsdf {
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SHADER_CLOSURE_BASE;
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} DiffuseBsdf;
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static_assert(sizeof(ShaderClosure) >= sizeof(DiffuseBsdf), "DiffuseBsdf is too large!");
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/* DIFFUSE */
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ccl_device int bsdf_diffuse_setup(ccl_private DiffuseBsdf *bsdf)
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{
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bsdf->type = CLOSURE_BSDF_DIFFUSE_ID;
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return SD_BSDF | SD_BSDF_HAS_EVAL;
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}
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ccl_device Spectrum bsdf_diffuse_eval(ccl_private const ShaderClosure *sc,
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const float3 wi,
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const float3 wo,
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ccl_private float *pdf)
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{
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ccl_private const DiffuseBsdf *bsdf = (ccl_private const DiffuseBsdf *)sc;
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float3 N = bsdf->N;
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float cosNO = fmaxf(dot(N, wo), 0.0f) * M_1_PI_F;
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*pdf = cosNO;
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return make_spectrum(cosNO);
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}
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ccl_device int bsdf_diffuse_sample(ccl_private const ShaderClosure *sc,
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float3 Ng,
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float3 wi,
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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 *wo,
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ccl_private float *pdf)
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{
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ccl_private const DiffuseBsdf *bsdf = (ccl_private const DiffuseBsdf *)sc;
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float3 N = bsdf->N;
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// distribution over the hemisphere
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sample_cos_hemisphere(N, randu, randv, wo, pdf);
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if (dot(Ng, *wo) > 0.0f) {
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*eval = make_spectrum(*pdf);
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}
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else {
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*pdf = 0.0f;
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*eval = zero_spectrum();
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}
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return LABEL_REFLECT | LABEL_DIFFUSE;
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}
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/* TRANSLUCENT */
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ccl_device int bsdf_translucent_setup(ccl_private DiffuseBsdf *bsdf)
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{
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bsdf->type = CLOSURE_BSDF_TRANSLUCENT_ID;
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return SD_BSDF | SD_BSDF_HAS_EVAL | SD_BSDF_HAS_TRANSMISSION;
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}
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ccl_device Spectrum bsdf_translucent_eval(ccl_private const ShaderClosure *sc,
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const float3 wi,
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const float3 wo,
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ccl_private float *pdf)
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{
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ccl_private const DiffuseBsdf *bsdf = (ccl_private const DiffuseBsdf *)sc;
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float3 N = bsdf->N;
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float cosNO = fmaxf(-dot(N, wo), 0.0f) * M_1_PI_F;
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*pdf = cosNO;
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return make_spectrum(cosNO);
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}
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ccl_device int bsdf_translucent_sample(ccl_private const ShaderClosure *sc,
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float3 Ng,
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float3 wi,
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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 *wo,
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ccl_private float *pdf)
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{
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ccl_private const DiffuseBsdf *bsdf = (ccl_private const DiffuseBsdf *)sc;
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float3 N = bsdf->N;
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// we are viewing the surface from the right side - send a ray out with cosine
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// distribution over the hemisphere
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sample_cos_hemisphere(-N, randu, randv, wo, pdf);
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if (dot(Ng, *wo) < 0) {
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*eval = make_spectrum(*pdf);
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}
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else {
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*pdf = 0;
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*eval = zero_spectrum();
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}
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return LABEL_TRANSMIT | LABEL_DIFFUSE;
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}
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CCL_NAMESPACE_END
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