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From: prevost@eos.UUCP (Michael Prevost)
Newsgroups: comp.sys.sgi
Subject: nurbs and bezier rendering
Keywords: nurbs
Message-ID: <5966@eos.UUCP>
Date: 11 Jan 90 22:21:12 GMT
Distribution: comp.sys.sgi
Organization: NASA Ames Research Center, California
Lines: 26


Can someone please give me some assistance with drawing 
parametric surfaces?  
I would like to alter a shaded parametric surface by changing a 
single control point for the surface. I need this affect to be be local, 
or at least not change the location of the end points. I can get the 
effect that I am looking for by using bezier curves ( GL patch 
command ) but I cannot seemed to render them as shaded surfaces, 
only lines. I haven't seen anything that says you cannot render them 
as shaded polygons but I've never seen an example of this either. 

I tried nurbs, which can be render as surfaces, but the end points 
drift as I change the control points and the curves doesn't have to 
pass through the any of the control points. The documentation says 
that the effect is local but also shows the end point moving. 

1) Is it possible to render bezier patches as shaded surfaces ?
2) Is it possible to restrict the end points of nurbs.

Thanks in advance

Mike Prevost 
Sterling Software 
NASA  AMES ms 239-19
Moffett Field Ca. 94035
prevost@eos.arc.nasa.gov