The RenderMan Interface - Paul Bourke

The actual change in a variable is equal to its derivative with respect to a surface
parameter times the change in the surface parameter. Thus, assuming forward differencing,
function(u+du)-function(u) = Du( function(u) ) * du;
function(v+dv)-function(v) = Dv( function(v) ) * dv;
float random()
color random ()
point random ()
random returns a float, color, or point whose components are a random number between
0 and 1.
float noise ( float v ), noise ( float u, v ), noise ( point pt ) noise ( point pt, float t )
color noise ( float v ), noise ( float u, v ), noise ( point pt ), noise ( point pt, float t )
point noise ( float v ), noise ( float u, v ), noise ( point pt ), noise ( point pt, float t )
vector noise ( float v ), noise ( float u, v ), noise ( point pt ), noise ( point pt, float t )
noise returns a value which is a pseuodrandom function of its arguments; its value
is always between 0 and 1. The domain of this noise function can be 1-D (one float),
2-D (two floats), 3-D (one point), or 4-D (one point and one float). These functions
can return any type. The type desired is indicated by casting the function to the type
desired. The following statement causes noise to return a color.
c = 2 * color noise(P);
float pnoise ( float v, uniform float period ),
pnoise ( float u, v, uniform float uperiod, uniform float vperiod ),
pnoise ( point pt, uniform point pperiod ),
pnoise ( point pt, float t, uniform point pperiod, uniform float tperiod )
color pnoise ( float v, uniform float period ),
pnoise ( float u, v, uniform float uperiod, uniform float vperiod ),
pnoise ( point pt, uniform point pperiod ),
pnoise ( point pt, float t, uniform point pperiod, uniform float tperiod )
point pnoise ( float v, uniform float period ),
pnoise ( float u, v, uniform float uperiod, uniform float vperiod ),
pnoise ( point pt, uniform point pperiod ),
pnoise ( point pt, float t, uniform point pperiod, uniform float tperiod )
vector pnoise ( float v, uniform float period ),
pnoise ( float u, v, uniform float uperiod, uniform float vperiod ),
pnoise ( point pt, uniform point pperiod ),
pnoise ( point pt, float t, uniform point pperiod, uniform float tperiod )
pnoise returns a value similar to noise with the same arguments, however, the value
returned by pnoise is periodic with period period (or pperiod, tperiod, etc.). That is,
pnoise(v, p) == pnoise(v+p, p). The period parameters must be uniform and have an
integer value (if it is a float expression), or lie on the integer lattice (if it is a point
expression).
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