Introduction
This tutorial covers the basic issues of dealing with RenderMan's
Curves and issues relating to the specification of their normals. A rib file can
either specify the surface normals of a curve or it can let the renderer orientate the
curve so that is always faces the camera. Figure 1 shows four colored Curves rendered without
their normals being specified.
Figure 1
The rib file that rendered the curves can be view here - curve_test.rib. It uses an archive rib file - b_spline.rib. So that the b-spline curve starts and ends at it's first and last control vertex their coordinates are specified 3 times.
Basis "b-spline" 1 "b-spline" 1
Curves "cubic" [8] "nonperiodic"
"P" [0 0 0 0 0 0 0 0 0
1 2 0 1.5 2 0
2 1 0 2 1 0 2 1 0]
"constantwidth" [0.125]
Figure 2 shows the same curves rendered with normals ("N"). It uses a modified rib archive
- b_spline_normals.rib
Figure 2