OpenSpace/shaders/floatoperations.glsl

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#ifndef _FLOATOPERATIONS_GLSL_
#define _FLOATOPERATIONS_GLSL_

/**
 * Convert a positive floating point distance [0, 10^27]
 * (size of observable universe)
 * to a float in the range [-1, 1], suitable for depth buffer storage.
 * Note: This needs to be a monotonic function, so that the value can
 * still be used for depth comparison.
 */
float normalizeFloat(float inpt) {
  if (inpt > 1.0) {
    return inpt / pow(10, 30);
  }
  else {
    return inpt - 1.0;
  }
}

float denormalizeFloat(float inpt) {
  if (inpt < 0.0) {
    return inpt + 1.0;
  }
  else {
    return inpt * pow(10, 30);
  }
}

/**
 * Compute the length of a vector.
 * Supporting huge vectors, where the square of any of the components is too large to be
 * represented as a float.
 */
float safeLength(vec4 v) {
  float m = max(max(max(abs(v.x), abs(v.y)), abs(v.z)), abs(v.w));
  if (m > 0.f) {
    return length(v / m) * m;
  }
  else {
    return 0.f;
  }
}

float safeLength(vec3 v) {
  return safeLength(vec4(v, 0.0));
}
float safeLength(vec2 v) {
  return safeLength(vec4(v, 0.0, 0.0));
}

#endif // _FLOATOPERATIONS_GLSL_