The RenderMan Interface - Paul Bourke

Function
abs(x)
Math Functions
Description
returns the absolute value of its argument.
acos(a) returns the arc cosine in the range 0 to π.
asin(a)
atan(yoverx), atan(y,x)
ceil(x)
cellnoise(v), cellnoise(u,v), cellnoise(pt),
cellnoise(pt,t)
clamp(a,min,max)
returns the arc sine in the range −π/2 to π/2.
with one argument returns the arc tangent in the
range −π/2 to π/2 (1 argument) or −π to π (2
arguments).
returns the largest integer (expressed as a float) not
greater than x.
returns a value which is a pseudorandom function
of its arguments and is constant within each cell defined
by integer lattice points, but discontinuous at
integer values. Its value is always between 0 and 1.
The domain of this function can be 1-D (one float),
2-D (two floats), 3-D (one point), or 4-D (one point
and one float).
returns min if a < min, max if a > max; otherwise
a.
cos(a) standard trigonometric function of radian
arguments.
degrees(rad)
converts from radians to degrees.
Du(p), Dv(p), Deriv(num,den) computes the derivatives of the arguments. The
type returned depends on the type of the first argument.
Du and Dv compute the derivatives in the u
and v directions, respectively. Deriv computes the
derivative of the first argument with respect to the
second argument.
exp(x)
filterstep(edge,s1,...)
floor(x)
log(x), log(x,base)
max(a,b,...)
min(a,b,...)
mix(color0, color1, value)
mod(a,b)
returns pow(e,x).
returns a filtered version of step.
returns the smallest integer (expressed as a float)
not smaller than x.
returns the natural logarithm of x (x=log(exp(x)))
(1 arg.) or the logarithm in the specified base
(x=log(pow(base,x),base)) (2 args).
returns the argument with maximum value.
returns the argument with minumum value.
returns a linearly interpolated color value.
returns 0