lottes.glsl

// Lottes 2016, "Advanced Techniques and Optimization of HDR Color Pipelines"
vec3 lottes(vec3 x) {
  const vec3 a = vec3(1.6);
  const vec3 d = vec3(0.977);
  const vec3 hdrMax = vec3(8.0);
  const vec3 midIn = vec3(0.18);
  const vec3 midOut = vec3(0.267);

  const vec3 b =
      (-pow(midIn, a) + pow(hdrMax, a) * midOut) /
      ((pow(hdrMax, a * d) - pow(midIn, a * d)) * midOut);
  const vec3 c =
      (pow(hdrMax, a * d) * pow(midIn, a) - pow(hdrMax, a) * pow(midIn, a * d) * midOut) /
      ((pow(hdrMax, a * d) - pow(midIn, a * d)) * midOut);

  return pow(x, a) / (pow(x, a * d) * b + c);
}

float lottes(float x) {
  const float a = 1.6;
  const float d = 0.977;
  const float hdrMax = 8.0;
  const float midIn = 0.18;
  const float midOut = 0.267;

  const float b =
      (-pow(midIn, a) + pow(hdrMax, a) * midOut) /
      ((pow(hdrMax, a * d) - pow(midIn, a * d)) * midOut);
  const float c =
      (pow(hdrMax, a * d) * pow(midIn, a) - pow(hdrMax, a) * pow(midIn, a * d) * midOut) /
      ((pow(hdrMax, a * d) - pow(midIn, a * d)) * midOut);

  return pow(x, a) / (pow(x, a * d) * b + c);
}

#pragma glslify: export(lottes)