The RenderMan Interface - Paul Bourke

typedef RtPointer
typedef RtPointer
RtLightHandle;
RtContextHandle;
All procedures and values defined in the interface are prefixed with Ri (for RenderMan
Interface). All types are prefixed with Rt (for RenderMan type). Boolean values are either
RI FALSE or RI TRUE. Special floating point values RI INFINITY and RI EPSILON are defined.
The expression −RI INFINITY has the obvious meaning. The number of components
in a color is initially three, but can be changed (See the section Additional options, p. 33). A
bound is a bounding box and is specified by 6 floating point values in the order xmin, xmax,
ymin, ymax, zmin, zmax. A matrix is an array of 16 numbers describing a 4 by 4 transformation
matrix. All multidimensional arrays are specified in row-major order, and points
are assumed to be represented as row vectors, not column vectors. For example, a 4 by 4
translation matrix to the location (2,3,4) is specified with
{ { 1.0, 0.0, 0.0, 0.0},
{ 0.0, 1.0, 0.0, 0.0},
{ 0.0, 0.0, 1.0, 0.0},
{ 2.0, 3.0, 4.0, 1.0} }
Tokens are strings that have a special meaning to procedures implementing the interface.
These meanings are described with each procedure. The capabilities of the RenderMan Interface
can be extended by defining new tokens and passing them to various procedures.
The most important of these are the tokens identifying variables defined by procedures
called shaders, written in the Shading Language. Variables passed through the Render-
Man Interface are bound by name to shader variables. To make the standard predeclared
tokens and user-defined tokens similar, RenderMan Interface tokens are represented by
strings. Associated with each of the standard predefined tokens, however, is a predefined
string constant that the RenderMan Interface procedures can use for efficient parsing. The
names of these string constants are derived from the token names used in this document
by prepending an RI to a capitalized version of the string. For example, the predefined
constant token for ”rgb” is RI RGB. The special predefined token RI NULL is used to specify
a null token.
In the C binding presented in this document, parameters are passed by value or by reference.
C implementations of the RenderMan Interface are expected to make copies of any
parameters whose values are to be retained across procedure invocations.
Many procedures in the RenderMan Interface have variable length parameter lists. These
are indicated by the syntactical construct ...parameterlist... in the procedure’s argument list.
In the C binding described, a parameterlist is a sequence of pairs of arguments, the first being
an RtToken and the second being an RtPointer, an untyped pointer to an array of either
RtFloat, RtString or other values. The list is terminated by the special token RI NULL.
In addition, each such procedure has an alternate vector interface, which passes the parameterlist
as three arguments: an RtInt indicating the length of the parameter list; an array of that
length that contains the RtTokens; and another array of the same length that contains the
RtPointers. This alternate procedure is denoted by appending an uppercase V to the procedure
name.
For example the procedure RiFoo declared as
8