Gaussian pseudo-random

The polar form of the Box-Muller transformation for calculating random variables with a Gaussian (or Normal) distribution.

on GetGausseRandom (mean, standardDeviation) 
  -- returns a standard Gaussian random number 
  -- based upon the polar form of the Box-Muller transform 
    w = 2.0 
  repeat while ( w >= 1.0 ) 
    x1 = 2.0 * (random(0,1000000)/1000000.0) - 1.0 
    x2 = 2.0 * (random(0,1000000)/1000000.0) - 1.0 
    w = x1 * x1 + x2 * x2 
  end repeat 
  w = sqrt( (-2.0 * log( w ) ) / w ) 
  r = (x1 * w) 
  if voidP(mean) then return r 
  return (mean + r * standardDeviation) 
end 

This function can be useful for creating 'weighted' randomness - ie random values that tend to congregate around an 'average' rather than being evenly spread across the range of possibilities. Here's an example of using Gaussian pseudo-random numbers to make piles of snow. Source Movie