light/common.h

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/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
 *
 * SPDX-License-Identifier: Apache-2.0 */
 
#pragma once
 
#include "kernel/types.h"
 
#include "kernel/sample/mapping.h"
 
CCL_NAMESPACE_BEGIN
 
/* Light Sample Result */
 
struct LightSample {
  float3 P;            /* position on light, or direction for distant light */
  packed_float3 Ng;    /* normal on light */
  float t;             /* distance to light (FLT_MAX for distant light) */
  float3 D;            /* direction from shading point to light */
  float u, v;          /* parametric coordinate on primitive */
  float pdf;           /* pdf for selecting light and point on light */
  float pdf_selection; /* pdf for selecting light */
  float eval_fac;      /* intensity multiplier */
  int object;          /* object id for triangle/curve lights */
  int prim;            /* lamp id for lights, primitive id for triangle/curve lights */
  int shader;          /* shader id */
  int group;           /* lightgroup */
  LightType type;      /* type of light */
  int emitter_id;      /* index in the emitter array */
};
 
/* Utilities */
 
ccl_device_inline float3 ellipse_sample(const float3 ru, const float3 rv, const float2 rand)
{
  const float2 uv = sample_uniform_disk(rand);
  return ru * uv.x + rv * uv.y;
}
 
ccl_device_inline float3 rectangle_sample(const float3 ru, const float3 rv, const float2 rand)
{
  return ru * (2.0f * rand.x - 1.0f) + rv * (2.0f * rand.y - 1.0f);
}
 
ccl_device float3 disk_light_sample(const float3 n, const float2 rand)
{
  float3 ru;
  float3 rv;
 
  make_orthonormals(n, &ru, &rv);
 
  return ellipse_sample(ru, rv, rand);
}
 
ccl_device float light_pdf_area_to_solid_angle(const float3 Ng, const float3 I, const float t)
{
  const float cos_pi = dot(Ng, I);
 
  if (cos_pi <= 0.0f) {
    return 0.0f;
  }
 
  return t * t / cos_pi;
}
 
/* Visibility flag om the light shader. */
ccl_device_inline bool is_light_shader_visible_to_path(const int shader, const uint32_t path_flag)
{
  if ((shader & SHADER_EXCLUDE_ANY) == 0) {
    return true;
  }
 
  if (((shader & SHADER_EXCLUDE_DIFFUSE) && (path_flag & PATH_RAY_DIFFUSE)) ||
      ((shader & SHADER_EXCLUDE_GLOSSY) && ((path_flag & (PATH_RAY_GLOSSY | PATH_RAY_REFLECT)) ==
                                            (PATH_RAY_GLOSSY | PATH_RAY_REFLECT))) ||
      ((shader & SHADER_EXCLUDE_TRANSMIT) && (path_flag & PATH_RAY_TRANSMIT)) ||
      ((shader & SHADER_EXCLUDE_CAMERA) && (path_flag & PATH_RAY_CAMERA)) ||
      ((shader & SHADER_EXCLUDE_SCATTER) && (path_flag & PATH_RAY_VOLUME_SCATTER)))
  {
    return false;
  }
 
  return true;
}
 
CCL_NAMESPACE_END