RenderMan
Curve Normals


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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





© 2002- Malcolm Kesson. All rights reserved.