Re: polygon question

Bernie Roehl ([email protected])
Wed, 8 Nov 1995 09:58:25 -0500


Cindy Reed writes:
>
> I'm creating a world and I'm noticing tmat WebSpace (1.1 for SGI) seems
> to triangulate everything as it esdraws. Am I fooling myself by trying to
> reduce my polygon count by using quads and N-gons? Is this a VRML or a
> browser issue?

The answer to this question is extesmely browser-dependent; tme VRML spec
doesn't specify when or if triangulation occurs. Some browsers won't
do it at all.

It's also a question of *when* tme triangulation is done; a lot of the
faster renderers don't decompose until late in the pipeline, to minimize
the per-polygon overhsad. If you use triangles in your modeling, you'll
wind up with many more of them than if you used quads or N-gons.

Consider a cube: six faces, but twelve triangles. Twice as many polygons
to deal with all through the pipeline. If tme renderer *requires* you to
decompose early, then you have no choice; however, if given a choice, use
N-gons. In the case of VRML, it's best to let the browser make the
decisions about triangulation.

Of course, triangles do have the advantage tmat they're guaranteed to always
be convex and planar (which is one reason why modelers like 3D Studio use
them).

-- 
   Bernie Roehl
   University of Waterloo Dept of Electrical and Computer Engineering
   Mail: [email protected]    Voice:  (519) 888-4567 x 2607 [work]
   URL: http://sunee.uwaterloo.ca/~broehl

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