/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
 *
 * SPDX-License-Identifier: Apache-2.0 */

#pragma once

// clang-format off
#include "kernel/closure/bsdf_ashikhmin_velvet.h"
#include "kernel/closure/bsdf_diffuse.h"
#include "kernel/closure/bsdf_oren_nayar.h"
#include "kernel/closure/bsdf_phong_ramp.h"
#include "kernel/closure/bsdf_diffuse_ramp.h"
#include "kernel/closure/bsdf_microfacet.h"
#include "kernel/closure/bsdf_burley.h"
#include "kernel/closure/bsdf_sheen.h"
#include "kernel/closure/bsdf_transparent.h"
#include "kernel/closure/bsdf_ray_portal.h"
#include "kernel/closure/bsdf_ashikhmin_shirley.h"
#include "kernel/closure/bsdf_toon.h"
#include "kernel/closure/bsdf_hair.h"
#include "kernel/closure/bsdf_principled_hair_chiang.h"
#include "kernel/closure/bsdf_principled_hair_huang.h"
// clang-format on

CCL_NAMESPACE_BEGIN

/* Returns the square of the roughness of the closure if it has roughness,
 * 0 for singular closures and 1 otherwise. */
ccl_device_inline float bsdf_get_specular_roughness_squared(const ccl_private ShaderClosure *sc)
{
  if (CLOSURE_IS_BSDF_SINGULAR(sc->type)) {
    return 0.0f;
  }

  if (CLOSURE_IS_BSDF_MICROFACET(sc->type)) {
    ccl_private MicrofacetBsdf *bsdf = (ccl_private MicrofacetBsdf *)sc;
    return bsdf->alpha_x * bsdf->alpha_y;
  }

  return 1.0f;
}

ccl_device_inline float bsdf_get_roughness_pass_squared(const ccl_private ShaderClosure *sc)
{
  if (sc->type == CLOSURE_BSDF_OREN_NAYAR_ID || sc->type == CLOSURE_BSDF_ROUGH_TRANSLUCENT_ID) {
    ccl_private OrenNayarBsdf *bsdf = (ccl_private OrenNayarBsdf *)sc;
    return sqr(sqr(bsdf->param.roughness));
  }

  /* For the Principled BSDF, we want the Roughness pass to return the value that
   * was set in the node. However, this value doesn't affect all closures (e.g.
   * diffuse), so skip those that don't really have a concept of roughness. */
  if (CLOSURE_IS_BSDF_DIFFUSE(sc->type)) {
    return -1.0f;
  }

  return bsdf_get_specular_roughness_squared(sc);
}

/* Widen the compact ray differential dD after a non-specular bounce so that
 * texture mip selection on subsequent hits reflects the BSDF lobe's angular
 * spread. This significantly save memory, and is needed to make image cache
 * memory usage scale with render tile size rather than overall resolution.
 *
 * This must be done consistently between next event estimation and forward
 * sampling for both to converge to the same result for MIS. This is not just
 * a theoretical concern, but can otherwise lead to seams.
 *
 * To achieve that, the sampled roughness is computed as a MIS weighted
 * average. This makes it so directions with high contribution from sharp
 * BSDFs have a lower roughness, as they will have a high MIS weight. */
ccl_device_forceinline float bsdf_widen_dD(const float prev_dD, const float avg_roughness_squared)
{
  if (!(avg_roughness_squared > 0.0f)) {
    return prev_dD;
  }

  return max(prev_dD, sqrtf(avg_roughness_squared));
}

/* An additional term to smooth illumination on grazing angles when using bump mapping
 * based on "A Microfacet-Based Shadowing Function to Solve the Bump Terminator Problem"
 * by Alejandro Conty Estevez, Pascal Lecocq, and Clifford Stein. It preserves detail
 * close to the shadow terminator, and doesn't "wash out" intermediate bumps using a
 * Cook-Torrance GGX function for shading. */
ccl_device_inline float bump_shadowing_term(const ccl_private ShaderData *sd,
                                            const ccl_private ShaderClosure *sc,
                                            const float3 I,
                                            const bool is_eval)
{
  if (isequal(sc->N, sd->N)) {
    return 1.0f;
  }

  /* Smoothing doesn't apply to curve geometry. */
  if (sd->type & PRIMITIVE_CURVE) {
    return 1.0f;
  }

  /* In order to avoid artifacts at the shadow terminator when using smooth normals,
   * the BSDF evaluation functions allow for light leaking through the actual geometry
   * and only checks that the directions are in the correct hemisphere w.r.t. the
   * shading normal.
   * However, when using bump/normal mapping, this can lead to light leaking not just
   * "around" the shadow terminator, but to the rear side of supposedly opaque geometry.
   * In order to detect this case, we can ensure that the direction is also valid w.r.t.
   * the smoothed (but non-bump-mapped) normal `sd->N` (or `Ns` for short below).
   *
   * `dot(Ns, I) * dot(Ns, N)` tells us if I and N are on the same side of the smoothed geometry.
   * If incoming(I) and normal(N) are on the same side we reject refractions, `dot(N, I) < 0`.
   * If they are on different sides we reject reflections, `dot(N, I) > 0`. */
  const float cosNsI = dot(sd->N, I);
  const float cosNsN = dot(sd->N, sc->N);
  const float cosNI = dot(sc->N, I);
  const bool is_diffuse = CLOSURE_IS_BSDF_DIFFUSE(sc->type);
  if (cosNsI * cosNsN * cosNI < 0.0f && (is_eval || is_diffuse)) {
    return 0.0f;
  }

  /* The above test applies to all closures, but the softening only applies to diffuse ones. */
  if (!is_diffuse) {
    return 1.0f;
  }

  /* When bump map correction is not used do skip the smoothing. */
  if ((sd->flag & SD_USE_BUMP_MAP_CORRECTION) == 0) {
    return 1.0f;
  }

  /* Get absolute incoming and shader normal deviation from smoothed normal, then clamp. */
  const float cos_i = fabsf(cosNsI);
  const float cos_d = fabsf(cosNsN);
  if (cos_d >= 1.0f || cos_i >= 1.0f) {
    return 1.0f;
  }
  if (cos_i < 1e-6f) {
    return 0.0f;
  }

  /* Get GGX shading values for final smoothing. */
  const float tan2_d = 1.0f / sqr(cos_d) - 1.0f;
  const float bump_alpha2 = saturatef(0.125f * tan2_d);

  /* Return smoothed value to avoid discontinuity at perpendicular angle. */
  return bsdf_G<MicrofacetType::GGX>(bump_alpha2, cos_i);
}

ccl_device_inline float shift_cos_in(float cos_in, const float frequency_multiplier)
{
  /* Shadow terminator workaround, taken from Appleseed.
   * SPDX-License-Identifier: MIT
   * Copyright (c) 2019 Francois Beaune, The appleseedhq Organization */
  cos_in = min(cos_in, 1.0f);

  const float angle = fast_acosf(cos_in);
  const float val = max(cosf(angle * frequency_multiplier), 0.0f) / cos_in;
  return val;
}

ccl_device_inline bool bsdf_is_transmission(const ccl_private ShaderClosure *sc, const float3 wo)
{
  return dot(sc->N, wo) < 0.0f;
}

ccl_device_inline int bsdf_sample(KernelGlobals kg,
                                  ccl_private ShaderData *sd,
                                  const ccl_private ShaderClosure *sc,
                                  const float3 rand,
                                  ccl_private Spectrum *eval,
                                  ccl_private float3 *wo,
                                  ccl_private float *pdf,
                                  ccl_private float2 *sampled_roughness,
                                  ccl_private float *eta)
{
  /* For curves use the smooth normal, particularly for ribbons the geometric
   * normal gives too much darkening otherwise. */
  *eval = zero_spectrum();
  *pdf = 0.f;
  int label = LABEL_NONE;
  const float3 Ng = (sd->type & PRIMITIVE_CURVE) ? sc->N : sd->Ng;
  const float2 rand_xy = make_float2(rand);

  switch (sc->type) {
    case CLOSURE_BSDF_DIFFUSE_ID:
      label = bsdf_diffuse_sample(sc, Ng, sd->wi, rand_xy, eval, wo, pdf);
      *sampled_roughness = one_float2();
      *eta = 1.0f;
      break;
#if defined(__SVM__) || defined(__OSL__)
    case CLOSURE_BSDF_OREN_NAYAR_ID:
      label = bsdf_oren_nayar_sample(
          sc, Ng, sd->wi, rand_xy, eval, wo, pdf, sampled_roughness, eta);
      break;
    case CLOSURE_BSDF_ROUGH_TRANSLUCENT_ID:
      label = bsdf_rough_translucent_sample(
          sc, Ng, sd->wi, rand_xy, eval, wo, pdf, sampled_roughness, eta);
      break;
#  ifdef __OSL__
    case CLOSURE_BSDF_BURLEY_ID:
      label = bsdf_burley_sample(sc, Ng, sd->wi, rand_xy, eval, wo, pdf);
      *sampled_roughness = one_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_PHONG_RAMP_ID:
      label = bsdf_phong_ramp_sample(sc, Ng, sd->wi, rand_xy, eval, wo, pdf, sampled_roughness);
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_DIFFUSE_RAMP_ID:
      label = bsdf_diffuse_ramp_sample(sc, Ng, sd->wi, rand_xy, eval, wo, pdf);
      *sampled_roughness = one_float2();
      *eta = 1.0f;
      break;
#  endif
    case CLOSURE_BSDF_TRANSLUCENT_ID:
      label = bsdf_translucent_sample(sc, Ng, sd->wi, rand_xy, eval, wo, pdf);
      *sampled_roughness = one_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_TRANSPARENT_ID:
      label = bsdf_transparent_sample(sc, Ng, sd->wi, eval, wo, pdf);
      *sampled_roughness = zero_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_RAY_PORTAL_ID:
      /* ray portals are not handled by the BSDF code, we should never get here */
      kernel_assert(false);
      break;
    case CLOSURE_BSDF_MICROFACET_GGX_ID:
    case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
    case CLOSURE_BSDF_MICROFACET_GGX_GLASS_ID:
      label = bsdf_microfacet_ggx_sample(
          kg, sc, Ng, sd->wi, rand, eval, wo, pdf, sampled_roughness, eta);
      break;
    case CLOSURE_BSDF_THIN_GLASS_TRANSMISSION_ID:
      label = bsdf_thin_glass_transmission_sample(
          kg, sc, Ng, sd->wi, rand, eval, wo, pdf, sampled_roughness, eta);
      break;
    case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_GLASS_ID:
      label = bsdf_microfacet_beckmann_sample(
          kg, sc, Ng, sd->wi, rand, eval, wo, pdf, sampled_roughness, eta);
      break;
    case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
      label = bsdf_ashikhmin_shirley_sample(
          sc, Ng, sd->wi, rand_xy, eval, wo, pdf, sampled_roughness);
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
      label = bsdf_ashikhmin_velvet_sample(sc, Ng, sd->wi, rand_xy, eval, wo, pdf);
      *sampled_roughness = one_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_DIFFUSE_TOON_ID:
      label = bsdf_diffuse_toon_sample(sc, Ng, sd->wi, rand_xy, eval, wo, pdf);
      *sampled_roughness = one_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_GLOSSY_TOON_ID:
      label = bsdf_glossy_toon_sample(sc, Ng, sd->wi, rand_xy, eval, wo, pdf);
      // double check if this is valid
      *sampled_roughness = one_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_HAIR_REFLECTION_ID:
      label = bsdf_hair_reflection_sample(
          sc, Ng, sd->wi, rand_xy, eval, wo, pdf, sampled_roughness);
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
      label = bsdf_hair_transmission_sample(
          sc, Ng, sd->wi, rand_xy, eval, wo, pdf, sampled_roughness);
      *eta = 1.0f;
      break;
#  ifdef __PRINCIPLED_HAIR__
    case CLOSURE_BSDF_HAIR_CHIANG_ID:
      label = bsdf_hair_chiang_sample(kg, sc, sd, rand, eval, wo, pdf, sampled_roughness);
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_HAIR_HUANG_ID:
      label = bsdf_hair_huang_sample(kg, sc, sd, rand, eval, wo, pdf, sampled_roughness);
      *eta = 1.0f;
      break;
#  endif
    case CLOSURE_BSDF_SHEEN_ID:
      label = bsdf_sheen_sample(sc, Ng, sd->wi, rand_xy, eval, wo, pdf);
      *sampled_roughness = one_float2();
      *eta = 1.0f;
      break;
#endif
    default:
      label = LABEL_NONE;
      break;
  }

  /* Test if BSDF sample should be treated as transparent for background. */
  if (label & LABEL_TRANSMIT) {
    const float threshold_squared = kernel_data.background.transparent_roughness_squared_threshold;

    if (threshold_squared >= 0.0f && !(label & LABEL_DIFFUSE)) {
      if (bsdf_get_specular_roughness_squared(sc) <= threshold_squared) {
        label |= LABEL_TRANSMIT_TRANSPARENT;
      }
    }
  }
  else if (label != LABEL_NONE) {
    /* Shadow terminator offset. */
    const float frequency_multiplier =
        kernel_data_fetch(objects, sd->object).shadow_terminator_shading_offset;
    if (frequency_multiplier > 1.0f) {
      const float cosNO = dot(*wo, sc->N);
      *eval *= shift_cos_in(cosNO, frequency_multiplier);
    }
    *eval *= bump_shadowing_term(sd, sc, *wo, false);
  }

#ifdef WITH_CYCLES_DEBUG
  kernel_assert(*pdf >= 0.0f);
  kernel_assert(eval->x >= 0.0f && eval->y >= 0.0f && eval->z >= 0.0f);
#endif

  return label;
}

ccl_device_inline void bsdf_roughness_eta(const ccl_private ShaderClosure *sc,
                                          const float3 wo,
                                          ccl_private float2 *roughness,
                                          ccl_private float *eta)
{
#ifdef __SVM__
  float alpha = 1.0f;
#endif
  switch (sc->type) {
    case CLOSURE_BSDF_DIFFUSE_ID:
      *roughness = one_float2();
      *eta = 1.0f;
      break;
#ifdef __SVM__
    case CLOSURE_BSDF_OREN_NAYAR_ID:
    case CLOSURE_BSDF_ROUGH_TRANSLUCENT_ID:
      *roughness = one_float2();
      *eta = 1.0f;
      break;
#  ifdef __OSL__
    case CLOSURE_BSDF_BURLEY_ID:
      *roughness = one_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_PHONG_RAMP_ID:
      alpha = phong_ramp_exponent_to_roughness(((const ccl_private PhongRampBsdf *)sc)->exponent);
      *roughness = make_float2(alpha, alpha);
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_DIFFUSE_RAMP_ID:
      *roughness = one_float2();
      *eta = 1.0f;
      break;
#  endif
    case CLOSURE_BSDF_TRANSLUCENT_ID:
      *roughness = one_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_TRANSPARENT_ID:
    case CLOSURE_BSDF_RAY_PORTAL_ID:
      *roughness = zero_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_MICROFACET_GGX_ID:
    case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
    case CLOSURE_BSDF_MICROFACET_GGX_GLASS_ID:
    case CLOSURE_BSDF_THIN_GLASS_TRANSMISSION_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_GLASS_ID: {
      const ccl_private MicrofacetBsdf *bsdf = (const ccl_private MicrofacetBsdf *)sc;
      *roughness = make_float2(bsdf->alpha_x, bsdf->alpha_y);
      *eta = (bsdf_is_transmission(sc, wo)) ? bsdf->ior : 1.0f;
      break;
    }
    case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID: {
      const ccl_private MicrofacetBsdf *bsdf = (const ccl_private MicrofacetBsdf *)sc;
      *roughness = make_float2(bsdf->alpha_x, bsdf->alpha_y);
      *eta = 1.0f;
      break;
    }
    case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
      *roughness = one_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_DIFFUSE_TOON_ID:
      *roughness = one_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_GLOSSY_TOON_ID:
      // double check if this is valid
      *roughness = one_float2();
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_HAIR_REFLECTION_ID:
      *roughness = make_float2(((ccl_private HairBsdf *)sc)->roughness1,
                               ((ccl_private HairBsdf *)sc)->roughness2);
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
      *roughness = make_float2(((ccl_private HairBsdf *)sc)->roughness1,
                               ((ccl_private HairBsdf *)sc)->roughness2);
      *eta = 1.0f;
      break;
#  ifdef __PRINCIPLED_HAIR__
    case CLOSURE_BSDF_HAIR_CHIANG_ID:
      alpha = ((ccl_private ChiangHairBSDF *)sc)->m0_roughness;
      *roughness = make_float2(alpha, alpha);
      *eta = 1.0f;
      break;
    case CLOSURE_BSDF_HAIR_HUANG_ID:
      alpha = ((ccl_private HuangHairBSDF *)sc)->roughness;
      *roughness = make_float2(alpha, alpha);
      *eta = 1.0f;
      break;
#  endif
    case CLOSURE_BSDF_SHEEN_ID:
      alpha = ((ccl_private SheenBsdf *)sc)->roughness;
      *roughness = make_float2(alpha, alpha);
      *eta = 1.0f;
      break;
#endif
    default:
      *roughness = one_float2();
      *eta = 1.0f;
      break;
  }
}

ccl_device_inline int bsdf_label(const KernelGlobals kg,
                                 const ccl_private ShaderClosure *sc,
                                 const float3 wo)
{
  /* For curves use the smooth normal, particularly for ribbons the geometric
   * normal gives too much darkening otherwise. */
  int label;
  switch (sc->type) {
    case CLOSURE_BSDF_DIFFUSE_ID:
    case CLOSURE_BSSRDF_BURLEY_ID:
    case CLOSURE_BSSRDF_RANDOM_WALK_ID:
    case CLOSURE_BSSRDF_RANDOM_WALK_SKIN_ID:
    case CLOSURE_BSSRDF_RANDOM_WALK_LEGACY_ID:
      label = LABEL_REFLECT | LABEL_DIFFUSE;
      break;
#ifdef __SVM__
    case CLOSURE_BSDF_OREN_NAYAR_ID:
      label = LABEL_REFLECT | LABEL_DIFFUSE;
      break;
#  ifdef __OSL__
    case CLOSURE_BSDF_BURLEY_ID:
      label = LABEL_REFLECT | LABEL_DIFFUSE;
      break;
    case CLOSURE_BSDF_PHONG_RAMP_ID:
      label = LABEL_REFLECT | LABEL_GLOSSY;
      break;
    case CLOSURE_BSDF_DIFFUSE_RAMP_ID:
      label = LABEL_REFLECT | LABEL_DIFFUSE;
      break;
#  endif
    case CLOSURE_BSDF_TRANSLUCENT_ID:
    case CLOSURE_BSDF_ROUGH_TRANSLUCENT_ID:
      label = LABEL_TRANSMIT | LABEL_DIFFUSE;
      break;
    case CLOSURE_BSDF_TRANSPARENT_ID:
      label = LABEL_TRANSMIT | LABEL_TRANSPARENT;
      break;
    case CLOSURE_BSDF_RAY_PORTAL_ID:
      label = LABEL_TRANSMIT | LABEL_RAY_PORTAL;
      break;
    case CLOSURE_BSDF_MICROFACET_GGX_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
    case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID:
    case CLOSURE_BSDF_MICROFACET_GGX_GLASS_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_GLASS_ID: {
      const ccl_private MicrofacetBsdf *bsdf = (const ccl_private MicrofacetBsdf *)sc;
      label = ((bsdf_is_transmission(sc, wo)) ? LABEL_TRANSMIT : LABEL_REFLECT) |
              ((bsdf_microfacet_eval_flag(bsdf)) ? LABEL_GLOSSY : LABEL_SINGULAR);
      break;
    }
    case CLOSURE_BSDF_THIN_GLASS_TRANSMISSION_ID:
      label = LABEL_TRANSMIT | LABEL_GLOSSY;
      break;
    case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
      label = LABEL_REFLECT | LABEL_GLOSSY;
      break;
    case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
      label = LABEL_REFLECT | LABEL_DIFFUSE;
      break;
    case CLOSURE_BSDF_DIFFUSE_TOON_ID:
      label = LABEL_REFLECT | LABEL_DIFFUSE;
      break;
    case CLOSURE_BSDF_GLOSSY_TOON_ID:
      label = LABEL_REFLECT | LABEL_GLOSSY;
      break;
    case CLOSURE_BSDF_HAIR_REFLECTION_ID:
      label = LABEL_REFLECT | LABEL_GLOSSY;
      break;
    case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
      label = LABEL_TRANSMIT | LABEL_GLOSSY;
      break;
#  ifdef __PRINCIPLED_HAIR__
    case CLOSURE_BSDF_HAIR_CHIANG_ID:
      if (bsdf_is_transmission(sc, wo)) {
        label = LABEL_TRANSMIT | LABEL_GLOSSY;
      }
      else {
        label = LABEL_REFLECT | LABEL_GLOSSY;
      }
      break;
    case CLOSURE_BSDF_HAIR_HUANG_ID:
      label = LABEL_REFLECT | LABEL_GLOSSY;
      break;
#  endif
    case CLOSURE_BSDF_SHEEN_ID:
      label = LABEL_REFLECT | LABEL_DIFFUSE;
      break;
#endif
    default:
      label = LABEL_NONE;
      break;
  }

  /* Test if BSDF sample should be treated as transparent for background. */
  if (label & LABEL_TRANSMIT) {
    const float threshold_squared = kernel_data.background.transparent_roughness_squared_threshold;

    if (threshold_squared >= 0.0f) {
      if (bsdf_get_specular_roughness_squared(sc) <= threshold_squared) {
        label |= LABEL_TRANSMIT_TRANSPARENT;
      }
    }
  }
  return label;
}

#ifndef __KERNEL_CUDA__
ccl_device
#else
ccl_device_inline
#endif
    Spectrum
    bsdf_eval(KernelGlobals kg,
              ccl_private ShaderData *sd,
              const ccl_private ShaderClosure *sc,
              const float3 wo,
              ccl_private float *pdf)
{
  Spectrum eval = zero_spectrum();
  *pdf = 0.f;

  const float bump_shadowing = bump_shadowing_term(sd, sc, wo, true);
  if (bump_shadowing == 0.0f) {
    return zero_spectrum();
  }

  switch (sc->type) {
    case CLOSURE_BSDF_DIFFUSE_ID:
      eval = bsdf_diffuse_eval(sc, sd->wi, wo, pdf);
      break;
#if defined(__SVM__) || defined(__OSL__)
    case CLOSURE_BSDF_OREN_NAYAR_ID:
      eval = bsdf_oren_nayar_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_ROUGH_TRANSLUCENT_ID:
      eval = bsdf_rough_translucent_eval(sc, sd->wi, wo, pdf);
      break;
#  ifdef __OSL__
    case CLOSURE_BSDF_BURLEY_ID:
      eval = bsdf_burley_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_PHONG_RAMP_ID:
      eval = bsdf_phong_ramp_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_DIFFUSE_RAMP_ID:
      eval = bsdf_diffuse_ramp_eval(sc, sd->wi, wo, pdf);
      break;
#  endif
    case CLOSURE_BSDF_TRANSLUCENT_ID:
      eval = bsdf_translucent_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_TRANSPARENT_ID:
      eval = bsdf_transparent_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_RAY_PORTAL_ID:
      eval = bsdf_ray_portal_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_MICROFACET_GGX_ID:
    case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
    case CLOSURE_BSDF_MICROFACET_GGX_GLASS_ID:
      eval = bsdf_microfacet_ggx_eval(kg, sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_THIN_GLASS_TRANSMISSION_ID:
      eval = bsdf_thin_glass_transmission_eval(kg, sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_GLASS_ID:
      eval = bsdf_microfacet_beckmann_eval(kg, sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
      eval = bsdf_ashikhmin_shirley_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_ASHIKHMIN_VELVET_ID:
      eval = bsdf_ashikhmin_velvet_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_DIFFUSE_TOON_ID:
      eval = bsdf_diffuse_toon_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_GLOSSY_TOON_ID:
      eval = bsdf_glossy_toon_eval(sc, sd->wi, wo, pdf);
      break;
#  ifdef __PRINCIPLED_HAIR__
    case CLOSURE_BSDF_HAIR_CHIANG_ID:
      eval = bsdf_hair_chiang_eval(kg, sd, sc, wo, pdf);
      break;
    case CLOSURE_BSDF_HAIR_HUANG_ID:
      eval = bsdf_hair_huang_eval(kg, sd, sc, wo, pdf);
      break;
#  endif
    case CLOSURE_BSDF_HAIR_REFLECTION_ID:
      eval = bsdf_hair_reflection_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_HAIR_TRANSMISSION_ID:
      eval = bsdf_hair_transmission_eval(sc, sd->wi, wo, pdf);
      break;
    case CLOSURE_BSDF_SHEEN_ID:
      eval = bsdf_sheen_eval(sc, sd->wi, wo, pdf);
      break;
#endif
    default:
      break;
  }

  eval *= bump_shadowing;

  /* Shadow terminator offset. */
  const float frequency_multiplier =
      kernel_data_fetch(objects, sd->object).shadow_terminator_shading_offset;
  if (frequency_multiplier > 1.0f) {
    const float cosNO = dot(wo, sc->N);
    if (cosNO >= 0.0f) {
      eval *= shift_cos_in(cosNO, frequency_multiplier);
    }
  }

#ifdef WITH_CYCLES_DEBUG
  kernel_assert(*pdf >= 0.0f);
  kernel_assert(eval.x >= 0.0f && eval.y >= 0.0f && eval.z >= 0.0f);
#endif
  return eval;
}

ccl_device void bsdf_blur(ccl_private ShaderClosure *sc, const float roughness)
{
  /* TODO: do we want to blur volume closures? */
#if defined(__SVM__) || defined(__OSL__)
  switch (sc->type) {
    case CLOSURE_BSDF_MICROFACET_GGX_ID:
    case CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID:
    case CLOSURE_BSDF_MICROFACET_GGX_GLASS_ID:
    case CLOSURE_BSDF_THIN_GLASS_TRANSMISSION_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID:
    case CLOSURE_BSDF_MICROFACET_BECKMANN_GLASS_ID:
      /* TODO: Recompute energy preservation after blur? */
      bsdf_microfacet_blur(sc, roughness);
      break;
    case CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID:
      bsdf_ashikhmin_shirley_blur(sc, roughness);
      break;
#  ifdef __PRINCIPLED_HAIR__
    case CLOSURE_BSDF_HAIR_CHIANG_ID:
      bsdf_hair_chiang_blur(sc, roughness);
      break;
    case CLOSURE_BSDF_HAIR_HUANG_ID:
      bsdf_hair_huang_blur(sc, roughness);
      break;
#  endif
    default:
      break;
  }
#endif
}

ccl_device_inline Spectrum bsdf_albedo(KernelGlobals kg,
                                       const ccl_private ShaderData *sd,
                                       const ccl_private ShaderClosure *sc,
                                       const bool reflection,
                                       const bool transmission)
{
  Spectrum albedo = sc->weight;
  /* Some closures include additional components such as Fresnel terms that cause their albedo to
   * be below 1. The point of this function is to return a best-effort estimation of their albedo,
   * meaning the amount of reflected/refracted light that would be expected when illuminated by a
   * uniform white background.
   * This is used for the denoising albedo pass and diffuse/glossy/transmission color passes.
   * NOTE: This should always match the sample_weight of the closure - as in, if there's an albedo
   * adjustment in here, the sample_weight should also be reduced accordingly.
   * TODO(lukas): Consider calling this function to determine the sample_weight? Would be a bit of
   * extra overhead though. */
#if defined(__SVM__) || defined(__OSL__)
  if (CLOSURE_IS_BSDF_MICROFACET(sc->type)) {
    albedo *= bsdf_microfacet_estimate_albedo(
        kg, sd->wi, (const ccl_private MicrofacetBsdf *)sc, reflection, transmission);
  }
#  ifdef __PRINCIPLED_HAIR__
  else if (sc->type == CLOSURE_BSDF_HAIR_CHIANG_ID) {
    /* TODO(lukas): Principled Hair could also be split into a glossy and a transmission component,
     * similar to Glass BSDFs. */
    albedo *= bsdf_hair_chiang_albedo(sd, sc);
  }
  else if (sc->type == CLOSURE_BSDF_HAIR_HUANG_ID) {
    albedo *= bsdf_hair_huang_albedo(sd, sc);
  }
#  endif
#endif
  return albedo;
}

CCL_NAMESPACE_END