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From: kahn@uxh.cso.uiuc.edu (Scott Kahn)
Newsgroups: comp.sys.sgi
Subject: VGX graphics and depthcueing
Message-ID: <1990Oct22.015204.24603@ux1.cso.uiuc.edu>
Date: 22 Oct 90 01:52:04 GMT
Sender: news@ux1.cso.uiuc.edu (News)
Organization: University of Illinois at Urbana
Lines: 28

I have found that generally speaking, the high-performance drawing
routines and depthcueing are not compatible on the VGX. That is,
on a GTX or PI one can intermix "v3f" and "lRGBcolor" freely, however
this does not work on the VGX. Apparently (according to the 3.3 man
page) one should not be doing this at all, and that it functions
on GTX and PI graphics is an "undocumented feature". Here's
the question:

If one desires to recolor each vertex of a tmesh, poly-line or
poly-point using depthcueing, can this be done on the VGX short
or digressing to simple triangles, two-point lines, and single
points?? While the alternative of using lighted lines has been
tried, sometimes depthcueing is preferred.

VGX observation two. It would seem that drawing tmeshes with arbitrarily
colored vertices (using two infinite light sources and three "lmcolor"
calls to alter vertex color characteristics) is actually FASTER on the
GTX rather than the VGX. Is this a generalization or can something
(no quad-mesh suggestions please!) be tuned on the VGX to enhance its
performance.

I will post whatever words of wisdom I receive...

Thanks,

Scott Kahn
Department of Chemistry
University of Illinois at Urbana-Champaign