Henrik Lind (hlind++at++bvu-lads.loral.com)
Fri, 17 May 1996 09:15:06 -0700 (PDT)
Henrik Lind
> +>---- On May 16, 5:02pm, Henrik Lind wrote:
> > Subject: Problem rendering smoke plume
> ->I am having difficulty rendering a smoke plume, composed of several
> ->semi-transparent textured polygons. The problem appears to be related
> ->to coplanarity based on viewing angle. I realize one can't avoid
> ->coplanarity, but I know it is possible to have a smoke plume look
> ->correct.
> ->
> ->At the coplanar condition, there is flashing, presumably between the
> ->coplanar polygons, until one is sufficiently separated from the other.
> ->I have verified that the polygons are correctly sorted for rendering
> ->back-to-front. The Performer transparency tokens I am using are
> ->PFTR_ON, PFTR_HIGH_QUALITY (we have an RE2), and PFTR_NO_OCCLUDE.
>
> This should work - the PFTR_HIGH_QUALITY will enable
> blending and the PFTR_NO_OCCLUDE will keep us from writing the
> zvalues that can potentially cause the coplanar fighting you
> complain about.
>
> ->What I wanted to do was to try the GL blendfunction() with
> ->arguments BF_SA and BF_MSA, but this is not possible with the
> ->PFTR_HIGH_QUALITY token, which is a must for us.
>
> PFTR_HIGH_QUALITY does PFTR_BLEND_ALPHA which will
> do blendfunction(BF_SA, BF_MSA) when the pfGeoState is applied.
>
> If you want yet a different blend function, you can put it in
> a pre-draw function for the pfGeoState via pfGStateFuncs().
>
>
> You might also want to use pfAlphaFunc to prevent pixels of very
> low alpha values from being written - just to help speed things up
> a bit.
>
> src.
>
>
> --
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> Sharon Rose Clay (Fischler) - Silicon Graphics, Advanced Systems Dev.
> src++at++sgi.com (415) 933 - 1002 FAX: (415) 965 - 2658 MS 8U-590
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>
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