Re: Shadow and projected texture

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Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Tue, 21 Jan 1997 13:27:11 +0000

On Jan 20, 8:41pm, Brian Furtaw wrote:
> Subject: Re: Shadow and projected texture
> On Jan 20, 6:25pm, Angus Dorbie wrote:
> > Subject: Re: Shadow and projected texture
> > On Jan 8, 6:15am, pere1++at++cluny.ensam.fr wrote:
> > > Subject: Shadow and projected texture
> > > Like Scott McMillan and Mark Baranowski, I try to make shadows with
> > > Performer 2.1 and Irix 6.2.
> > >
> > > Remi ARNAUD says:
> > > > OpenGL shadows are not supported by Performer 2.x, but the OpenGL
shadow
> > > > extensions are in the patch 1355 for 6.2.
> > >
> > > Is this the solution ? if, it is, ok I will install this patch.
> >
> > Well what Remi has just said means that 1355 is essential but even with
> > it it's not a solution: "OpenGL shadows are not supported by Performer 2.x"
> >
> > Compile for IrisGL and perhaps this will support the shadows via IrisGL
> > and IGLOO.
> >
> > Failing this you'll have to hand code the OpenGL shadows multi-pass.
> >
> > Cheers,
> > Angus.
> >
> > =======================================================================
> > List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
> > Submissions: info-performer++at++sgi.com
> > Admin. requests: info-performer-request++at++sgi.com
> >-- End of excerpt from Angus Dorbie
>
>

Brian,
For the sake of avoiding confusion:

Remi clearly stated that you need patch 1355 for shadows in OpenGL.
If you have shadows in OpenGL you can support this yourself
using performer but the support Remi is talking about is automatic
shadows using performers multipass capability; PFTRAV_MULTIPASS and
the pflightsource; PFLS_SHADOW_ENABLE. This works for an IrisGL
compile in Performer but not OpenGL.

I hope this is clearer now.

Cheers,
Angus.

> Angus,
> I think Remi was trying to say that performer does not have a node that
> implements OpenGL shadows. Not that OpenGL shadow extension would not work.
> Even with the OpenGL shadow extension you still have to do two passes one
> to render to the depth buffer from the point view of the light source. Then
> in the final pass you load the depth buffer information into the texture
> memory using the OpenGL extension and render from the point of view of the
> observer. You can read about this in glintro. SO you will need to draw the
> channel twice with two different viewpoints. The OpenGL calls can be put
> into a post-draw callback.
>
> Brian
>
> --
> o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o
>
> Brian Furtaw (brian++at++sgi.com)
> VisSim Technical Consultant
> 12200-G Plum Orchard Drive Office: (301)572-3293 Fax: (301)872-3293
> Silver Spring, Maryland 20904 OpenGL/ImageVision/OpenInventor/Performer
>-- End of excerpt from Brian Furtaw

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