Re: Layer anomalies
John Rohlf (jrohlf++at++tubes)
Tue, 20 Jun 95 9:51:01 PDT
>
> >
> > Performer uses displacepolygon() for fast rendering
> >and stencil() for not-so-fast rendering of coplanar geometry.
> >Unfortunately, IrisGL's displacepolygon() is inadequate in
> >certain situations - you can see poke through when layers
> >have large z-slopes and flimmering when they have small z-slopes.
> >
> > Note that if you specify PFDECAL_BASE_HIGH_QUALITY when
> >building your Performer database (See pfLayerMode) you will always get
> >accurate coplanar rendering. You need not call stensize() nor stencil().
> >
> > I am currently working on a fix for the
> >displacepolygon() problem that will be available in 2.0
> >and will experiment with your database.
> >
>
> John Rohlf
>
> You are right PFDECAL_BASE_HIGH_QUALITY will render coplanar polygons
> correctly on our database, we have tried that in our lab and it works on
> an Onyx and Crimson.The problem is that we need this to work on a Indig^2
> Extreme which supports 4 stencil planes. If I understand this correctly it
> means that the Indigo^2 Extreme can support up to 16 layers. Well I find
> hard to believe that we need more than that in our database so that it can
> be rendered correctly.
Performer needs only a single stencil plane for rendering
any number of PFDECAL_BASE_STENCIL layers. However, base and
layer geometry must be rendered sequentially which obviates any
benefits from mode sorting.
2.0 has a pseudo-fix to the displacepolygon() poke-through
problem but the real fix comes with OpenGL where glPolygonOffset
has both a scale and an offset.
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on Mon Aug 10 1998 - 17:51:36 PDT