The RenderMan Interface - Paul Bourke

Section 3
RELATIONSHIP TO THE RENDERMAN SHADING
LANGUAGE
The capabilities of the RenderMan Interface can be extended by using the Shading Language.
The Shading Language is described in Part II of this document. This section describes
the interaction between the RenderMan Interface and the Shading Language.
Special procedures, called shaders, are declared in this language. The argument list of a
shader declares variables that can be passed through the RenderMan Interface to a shader.
For example, in the shading language a shader called weird might be declared as follows:
surface
weird ( float f = 1.0; point p = (0,0,0) )
{
Cs = Ci * mod ( length(P-p)*f - s + t, 1.0 );
}
The shader weird is referred to by name and so are its variables.
RtFloat foo;
RtPoint bar;
RiSurface (”weird”, ”f”, (RtPointer)&foo, ”p”, (RtPointer)&bar, RI NULL);
passes the value of foo to the Shading Language variable f and the value bar to the variable
p. Note that since all parameters are passed as arrays, the single float must be passed by
reference.
In order to pass shading language variables, the RenderMan Interface must know the type
of each variable defined in a shader. All predefined shaders predeclare the types of the
variables that they use. Certain other variables, such as position, are also predeclared.
Additional variables are declared with:
RtToken
RiDeclare (char *name, char *declaration)
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