// used in global_settings, sets the type of noise computation
// there are 3 available noise generators
// they can be used for single pigments, etc. too by adding
// noise_generator x to the definition
  //noise_generator 1 // old 3.1g plateaud noise
  //noise_generator 2 // fixed version of 3.1 noise
global_settings{ noise_generator 3 }  // New 3.5 perlin noise