Re: Shadow and projected texture

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Brian Furtaw (brian++at++sgi.com)
Mon, 20 Jan 1997 20:41:57 -0500

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.
>
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>-- End of excerpt from Angus Dorbie

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

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