bsdf_diffuse.h

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/* SPDX-FileCopyrightText: 2009-2010 Sony Pictures Imageworks Inc., et al. All Rights Reserved.
 * SPDX-FileCopyrightText: 2011-2022 Blender Foundation
 *
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Adapted code from Open Shading Language. */
 
#pragma once
 
#include "kernel/types.h"
 
#include "kernel/sample/mapping.h"
 
CCL_NAMESPACE_BEGIN
 
struct DiffuseBsdf {
  SHADER_CLOSURE_BASE;
};
 
static_assert(sizeof(ShaderClosure) >= sizeof(DiffuseBsdf), "DiffuseBsdf is too large!");
 
/* DIFFUSE */
 
ccl_device int bsdf_diffuse_setup(ccl_private DiffuseBsdf *bsdf)
{
  bsdf->type = CLOSURE_BSDF_DIFFUSE_ID;
  return SD_BSDF | SD_BSDF_HAS_EVAL;
}
 
ccl_device Spectrum bsdf_diffuse_eval(const ccl_private ShaderClosure *sc,
                                      const float3 /*wi*/,
                                      const float3 wo,
                                      ccl_private float *pdf)
{
  const ccl_private DiffuseBsdf *bsdf = (const ccl_private DiffuseBsdf *)sc;
  const float3 N = bsdf->N;
 
  const float cosNO = fmaxf(dot(N, wo), 0.0f) * M_1_PI_F;
  *pdf = cosNO;
  return make_spectrum(cosNO);
}
 
ccl_device int bsdf_diffuse_sample(const ccl_private ShaderClosure *sc,
                                   const float3 Ng,
                                   const float3 /*wi*/,
                                   const float2 rand,
                                   ccl_private Spectrum *eval,
                                   ccl_private float3 *wo,
                                   ccl_private float *pdf)
{
  const ccl_private DiffuseBsdf *bsdf = (const ccl_private DiffuseBsdf *)sc;
  const float3 N = bsdf->N;
 
  // distribution over the hemisphere
  sample_cos_hemisphere(N, rand, wo, pdf);
 
  if (dot(Ng, *wo) > 0.0f) {
    *eval = make_spectrum(*pdf);
  }
  else {
    *pdf = 0.0f;
    *eval = zero_spectrum();
  }
  return LABEL_REFLECT | LABEL_DIFFUSE;
}
 
/* TRANSLUCENT */
 
ccl_device int bsdf_translucent_setup(ccl_private DiffuseBsdf *bsdf)
{
  bsdf->type = CLOSURE_BSDF_TRANSLUCENT_ID;
  return SD_BSDF | SD_BSDF_HAS_EVAL | SD_BSDF_HAS_TRANSMISSION;
}
 
ccl_device Spectrum bsdf_translucent_eval(const ccl_private ShaderClosure *sc,
                                          const float3 /*wi*/,
                                          const float3 wo,
                                          ccl_private float *pdf)
{
  const ccl_private DiffuseBsdf *bsdf = (const ccl_private DiffuseBsdf *)sc;
  const float3 N = bsdf->N;
 
  const float cosNO = fmaxf(-dot(N, wo), 0.0f) * M_1_PI_F;
  *pdf = cosNO;
  return make_spectrum(cosNO);
}
 
ccl_device int bsdf_translucent_sample(const ccl_private ShaderClosure *sc,
                                       const float3 Ng,
                                       const float3 /*wi*/,
                                       const float2 rand,
                                       ccl_private Spectrum *eval,
                                       ccl_private float3 *wo,
                                       ccl_private float *pdf)
{
  const ccl_private DiffuseBsdf *bsdf = (const ccl_private DiffuseBsdf *)sc;
  const float3 N = bsdf->N;
 
  // we are viewing the surface from the right side - send a ray out with cosine
  // distribution over the hemisphere
  sample_cos_hemisphere(-N, rand, wo, pdf);
  if (dot(Ng, *wo) < 0) {
    *eval = make_spectrum(*pdf);
  }
  else {
    *pdf = 0;
    *eval = zero_spectrum();
  }
  return LABEL_TRANSMIT | LABEL_DIFFUSE;
}
 
CCL_NAMESPACE_END