  * http://mathworld.wolfram.com/SpherePointPicking.html
  */
 vec3 randomSpherePoint_(vec3 rand) {
-  float ang1 = (rand.x + 1.0) * PI; // 2.0 * [0..1) * PI
+  float ang1 = (rand.x + 1.0) * PI; // [-1..1) -> [0..2*PI)
   float u = rand.y; // [-1..1), cos and acos(2v-1) cancel each other out, so we arrive at [-1..1)
   float u2 = u * u;
   float x = sqrt(1.0 - u2) * cos(ang1);

/**
 * Generate a uniformly distributed random point on the unit-hemisphere
 * around the given normal vector.
 * 
 * The points are uniform over the sphere and NOT over the projected disk
 * of the sphere, so this function cannot be used when sampling a spherical


/**
 * Generate a random value in [-1..+1).
 * 
 * The distribution MUST be really uniform and exhibit NO pattern at all,
 * because it is heavily used to generate random sample directions for various
 * things, and if the random function contains the slightest pattern, it will
