Normals facing away from viewer

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#119

From: Dan S Reznik
Date: Fri, 22 Jan 1993 22:45

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I am drawing a cylindrical surface in 3D using quadrilateral patches
(shademodel(FLAT)), with zbuffer(TRUE), using GL's defualt lighting
settings. The problem is that the inside patches aredrawn black since
their normals are facing away from the viewer and I think the lighting
calculations don't work right. How can I change this situation ? I
tryied turing on TWO-SIDED lighting but this seems not to work on our
Personal Iris 4D20. A software solution I thought of is to preprocess
the patches and flip the normals [ mult by (-1, -1, -1) ] for the
polygons found to be backfacing. Any suggestions ?

Dan

P.S - Email responses preferred since I don't subscribe here.

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Path: arc1-ca.pugleaf.net!sparky!uunet!olivea!pagesat!a2i!sgiblab!sdd.hp.com!saimiri.primate.wisc.edu!doug.cae.wisc.edu!robios.me.wisc.edu!reznik
From: reznik@robios.me.wisc.edu (Dan S Reznik)
Newsgroups: comp.sys.sgi.graphics
Subject: Normals facing away from viewer
Message-ID: <REZNIK.93Jan22144545@robios2.me.wisc.edu>
Date: 22 Jan 93 22:45:45 GMT
Distribution: comp.sys.sgi,comp.sys.sgi.graphics
Organization: U. Wisconsin-Madison, Robotics Laboratory
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