The RenderMan Interface - Paul Bourke

SEE ALSO
2 2 [ 0 0 1 1 ] 0 1
”Pw” [ 1 0 0 1 1 1 0 1 0 2 0 2
-1 1 0 1 -1 0 0 1 -1 -1 0 1
0 -2 0 2 1 -1 0 1 1 0 0 1
1 0 -3 1 1 1 -3 1 0 2 -6 2
-1 1 -3 1 -1 0 -3 1 -1 -1 -3 1
0 -2 -6 2 1 -1 -3 1 1 0 -3 1 ]
RiPatch, RiPatchMesh, RiTrimCurve
RiTrimCurve ( RtInt nloops, RtInt ncurves[], RtInt order[], RtFloat knot[],
RtFloat min, RtFloat max, RtInt n[], RtFloat u[], RtFloat v[], RtFloat w[] )
Set the current trim curve. The trim curve contains nloops loops, and each of these
loops contains ncurves curves. The total number of curves is equal to the sum of all
the values in ncurves. Each of the trimming curves is a non-uniform rational B-spline
curve in homogeneous parameter space (u,v,w). The curves of a loop connect in headto-tail
fashion and must be explicitly closed. The arrays order, knot, min, max, n, u, v,
w contain the parameters describing each trim curve. All the trim curve parameters
are concatenated together into single large arrays. The meanings of these parameters
are the same as the corresponding meanings for a non-uniform B-spline surface.
Trim curves exclude certain areas from the non-uniform B-spline surface definition.
The inside must be specified consistently using two rules: an odd winding rule that
states that the inside consists of all regions for which an infinite ray from any point
in the region will intersect the trim curve an odd number of times, and a curve orientation
rule that states that the inside consists of the regions to the “left” as the curve
is traced.
Trim curves are typically used to specify boundary representations of solid models.
Since trim curves are approximations and not exact, some artifacts may occur at the
boundaries between intersecting output primitives. A more accurate method is to
specify solids using spatial set operators or constructive solid geometry (CSG). This
is described in the section on Solids and Spatial Set Operations, p. 92.
The list of Trim Curves is part of the attribute state, and may be saved and restored
using RiAttributeBegin and RiAttributeEnd.
RIB BINDING
TrimCurve ncurves order knot min max n u v w
The number of loops is determined implicitly by the length of the ncurves array.
EXAMPLE
RtInt nloops = 1;
RtInt ncurves[1] = { 1 };
RtInt order[1] = { 3 };
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