This function returns a sandy pattern.
The return value will be float, point, vector, normal or color 
depending on the cast, whose component(s) lie in the range [0,1].
The higher the frequency, the finer the grain.

This must be a varying float.  The default is the surface parameter, u.
This is the seed for the noise function.

This must be a float.  The default is 8.0.
This is the frequency of the noise.
The higher the frequency, the finer the grain.

This function returns a sandy pattern.
The return value will be float, point, vector, normal or color 
depending on the cast, whose component(s) lie in the range [0,1].
The higher the frequency, the finer the grain.