Rob Jenkins (robj++at++quid.engr.sgi.com)
Tue, 28 Apr 1998 08:18:44 -0700
o Triangles that should be drawn, not being drawn ( leaving gaps ) OR
o Triangles that should not be drawn, being drawn ( overwriting existing
geometry ) OR
o Triangles being drawn correctly but with incorrect lighting applied to them.
I've seen the third case before where random triangles were not lit which made
it look like random black triangles were drawn, try clearing the background to
a color other than black so you can see if you have a gap or a badly lit tri.
Also draw the geometry with a wireframe outline ( as per perfly, in fact load
the scene into perfly to experiment ). When you tried with perfly before did
you draw the same number of channels as your CAVE app does ? If not then try
that and see what it's like. If perfly doesn't show the same problem with the
same data then try to narrow down the differences between your app and perfly
in terms of data loading, lighting, viewing frustrum etc
Not much specific help I'm afraid but it might help you define the problem in
more detail.
Cheers
Rob
On Apr 28, 11:01am, Alejandro Saez wrote:
> Subject: Re: ghost polygons
> On Apr 28, 11:30am, Liu Xiaoyan wrote:
> > Subject: Re: ghost polygons
> > > > For certain models displayed in our performer applcation, there are
> > > > some ghost polygons flashing around. While viewed in IVVIEW or
> > > > saved as .pfb files, they are gone. What's happening? The machine
> > > > used is Onyx2 with 2 IR , performer 2.1.
> > >
> > > Depends on what you mean by "ghost polygons". Might be a problem with
> > > your models where there are polygons with their back-faces enabled. >Can
> you be a bit more specific to help us exorcise your ghosts ?
> > >
> >
> > By 'ghost ploygons' I mean they don't exsit at all in our original
> > geometry when built in Alias and other software. After exported to .iv
> > and viewed in perfly, ivview , they don't come out. Only in our
> > CAVE performer application do they appear.
> >
> > They are mostly in the form of triangles(with two-sided lighting
> > on or off), appear randomly depend on my eye position. Our application
> > is basically a 4 channel(2 channels share a pipe) program.
> >
> > Thanks.
> >
> > Liu
> > =======================================================================
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> >-- End of excerpt from Liu Xiaoyan
>
> Could it be a Z buffer resolution problem??? Make sure you have enough Z bits
> and that the far/near plane ratio doesn't exceed around 10000. Different
> programs might have different default settings, thus triggering the effect.
>
> --
> ------------------------------------------------------------------------
> Alejandro Saez
> Software Engineer
> Silicon Chile S.A.
> Avda. Andres Bello 2777, Of. 602
> E-mail: asaez++at++silicon.cl Providencia
> Phone: +56 (2) 203 3371 Ext. 105 Santiago
> Fax: +56 (2) 203 3370 Chile
> ------------------------------------------------------------------------
> =======================================================================
> List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
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>-- End of excerpt from Alejandro Saez
--
________________________________________________________________
Rob Jenkins mailto:robj++at++sgi.com
Silicon Graphics, Mtn View, California, USA
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This archive was generated by hypermail 2.0b2 on Mon Aug 10 1998 - 17:57:18 PDT