From: RJM Smeenk (r.j.m.smeenk++at++fel.tno.nl)
Date: 03/30/2005 04:30:14
Hello all,
I am running into a bug in the pfdGeoBuilder that apparently already
exists a couple of years.
(See mailing list archive
http://oss.sgi.com/projects/performer/mail/info-performer/perf-01-11/0007.html)
The bug appears when using shaders for performing the lighting of
geometry. The shader needs per vertex normals, but because they are
wrong I will not be able to recreate the fixed function pipeline
correctly.
You can find a test program that demonstrates the problem (based on
complex.C) here:
http://www.smeenk.com/performer/normals.C
It creates two sets of triangles and visualizes the normals by mapping
the xyz to colors with help a shaderprogram. The triangles on the left
show the problem of inconsistent normals (different colors), the
triangles on the right show the expected behaviour.
Both have per vertex normals, but the set on the right has a slight
difference in the normals (which when normalized will be the same normal
again). The program was tested on a Linux system with Performer 3.2, and
an ATI X800 graphics card with the latest ATI Linux drivers 8.10.19.
Note that you will need GLSL support to run this program.
Hopefully somebody can help me out, since all my shaders are useless
because of this problem.
kind regards,
Roland Smeenk
PS. This may also be the cause of the incomplete set of normals that is
displayed when using the normal highlight mode in Perfly.
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