[rohitarondekar]

They are generated randomly. Ken Perlin has described it in his book Texturing, Modeling A Procedural Approach. If I remember correctly the numbers have to be such that every direction should have an equal chance. Even distribution I think.

[J3L2404]

I was thinking it would be more like the fast inverse square from Quake. If it's random, using the same code could be a problem, no?