import lib-defines.glsl

//: param auto texture_environment 
uniform sampler2D environment_texture; 
//: param auto environment_rotation 
uniform float environment_rotation; 
//: param auto environment_exposure 
uniform float environment_exposure; 
//: param auto environment_irrad_mat_red 
uniform mat4 irrad_mat_red; 
//: param auto environment_irrad_mat_green 
uniform mat4 irrad_mat_green; 
//: param auto environment_irrad_mat_blue 
uniform mat4 irrad_mat_blue;

vec3 envSampleLOD(vec3 dir, float lod) 
{ 
  // WORKAROUND: Intel GLSL compiler for HD5000 is bugged on OSX: 
  // https://bugs.chromium.org/p/chromium/issues/detail?id=308366 
  // It is necessary to replace atan(y, -x) by atan(y, -1.0 * x) to force 
  // the second parameter to be interpreted as a float 
  vec2 pos = M_INV_PI * vec2(atan(-dir.z, -1.0 * dir.x), 2.0 * asin(dir.y)); 
  pos = 0.5 * pos + vec2(0.5); 
  pos.x += environment_rotation; 
  return textureLod(environment_texture, pos, lod).rgb * environment_exposure; 
}

vec3 envIrradiance(vec3 dir) 
{ 
  float rot = environment_rotation * M_2PI; 
  float crot = cos(rot); 
  float srot = sin(rot); 
  vec4 shDir = vec4(dir.xzy, 1.0); 
  shDir = vec4( 
    shDir.x * crot - shDir.y * srot, 
    shDir.x * srot + shDir.y * crot, 
    shDir.z, 
    1.0); 
  return max(vec3(0.0), vec3( 
      dot(shDir, irrad_mat_red * shDir), 
      dot(shDir, irrad_mat_green * shDir), 
      dot(shDir, irrad_mat_blue * shDir) 
    )) * environment_exposure; 
}