The RenderMan Interface - Paul Bourke

float cellnoise ( float v ), cellnoise ( float u, v ),
cellnoise ( point pt ) cellnoise ( point pt, float t )
color cellnoise ( float v ), cellnoise ( float u, v ),
cellnoise ( point pt ), cellnoise ( point pt, float t )
point cellnoise ( float v ), cellnoise ( float u, v ),
cellnoise ( point pt ), cellnoise ( point pt, float t )
vector cellnoise ( float v ), cellnoise ( float u, v ),
cellnoise ( point pt ), cellnoise ( point pt, float t )
cellnoise returns a value which is a pseuodrandom function of its arguments. Its
domain can be 1-D (one float), 2-D (two floats), 3-D (one point), or 4-D (one point
and one float). Its return value is uniformly distributed between 0 and 1, has constant
value between integer lattice points, and is discontinuous at integer locations. This is
useful if you are dividing space into regions (“cells”) and want a different (repeatable)
random number for each region. It is considerably cheaper than calling noise, and
thus is preferable if you have been using noise simply to generate repeatable random
sequences. The type desired is indicated by casting the function to the type desired.
15.2 Geometric Functions
Geometric functions provide a kernel of useful geometric operations. Most of these functions
are most easily described by just giving their implementation.
float xcomp( ptype P )
float ycomp( ptype P )
float zcomp( ptype P )
void setxcomp( output ptype P; float x )
void setycomp( output ptype P; float y )
void setzcomp( output ptype P; float z )
These functions get and set individual components of points, vectors, or normals.
float
length( vector V )
{
return sqrt(V.V);
}
Return the length of a vector.
vector
normalize( vector V )
{
return V/length(V);
}
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