The RenderMan Interface - Paul Bourke

15.7.1 Basic texture maps
Basic texture maps return either floats or colors.
float texture ( string name[channel]; [texture coordinates,] [parameterlist] )
color texture ( string name[channel]; [texture coordinates,] [parameterlist] )
where texture coordinates is one of the following:
float s, t;
float s1,t1, s2,t2, s3,t3, s4,t4;
Return the filtered texture value. The cast before the function determines the type
returned, either a float or a color. The name is the name of the texture map created
using RiMakeTexture. The channel selector is optional; if it is not present, the brackets
are also omitted and channel 0 is assumed. channel selects the starting channel
in the texture. The number of channels returned depends on whether the texture
is interpreted as a float or a color. texture coordinates are also optional. If present
they consist either of a single 2-D coordinate or four 2-D coordinates. If no texture
coordinates are given, the current values of (s,t) are used. parameterlist is a list of
name-value pairs that allow greater control over texture access.
Some examples of the use of this function are:
c = texture( ”logo” [0] );
c = color texture ( ”logo” );
c = color texture ( ”logo”, 2*s, 4*t );
In the first two cases, the texture coordinates are the current values of the predefined
variables (s,t).
15.7.2 Environment maps
float environment ( string name[channel]; texture coordinates, [parameterlist] )
color environment ( string name[channel]; texture coordinates, [parameterlist] )
where texture coordinates is one of the following:
point R;
point R1, R2, R3, R4;
Return the filtered texture value from an environment map. The cast before the function
determines the type returned, either a float or a color. The name is the name
of the texture map created using RiMake...Environment. The channel selector is optional;
if it is not present, the brackets are also omitted and channel 0 is assumed.
channel selects the starting channel in the texture. The number of channels returned
depends on whether the texture is interpreted as a float or a color. This function expects
either a single texture coordinate or four texture coordinates. These are points
that are used to define a direction in space. The length of this vector is unimportant.
parameterlist is a list of name-value pairs which allow greater control over texture
access.
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