Brian Furtaw (brian++at++sgi.com)
Mon, 18 Nov 1996 13:03:51 -0500
Availiable in OpenGL on the IR today Performer-2.1 are some extensions which
allow you to do multipass rendering of shadows. man on glTexParameter(3G)
should give you some insight, here are some excerpts from glIntro(3G)
glIntro(3G) OpenGL Reference glIntro(3G)
SGIX_shadow
provides support for rendering shadows using shadow maps. First the
application renders the scene from the point of view of the light
source, and copies the resulting depth buffer to a texture with
internal format GL_DEPTH_COMPONENT. Next the application renders
the scene from the normal viewpoint. Then the application enables
the texture parameter GL_TEXTURE_COMPARE_SGIX, sets the texture
comparison operator and texture matrix appropriately, and re-renders
the scene with 2D texturing enabled. During this final rendering
pass, the depth value generated by iterating the r texture
coordinate is compared with the shadow map stored in texture memory,
and the results of the comparison indicate whether the pixel being
textured is in shadow. The filtered result of the shadow
comparisons can be blended with the pixel to darken it. Supported
on InfiniteReality systems. For more information, see
glTexParameter.
SGIX_shadow_ambient
controls the filtered texture value generated in shadowed regions
(see SGIX_shadow). In effect, this changes the ambient lighting in
shadows. Supported on InfiniteReality systems. For more
information, see glTexParameter.
I haven't tried these features myself so I am not quite sure how to make them
work. I will try to find out and forward the information to you.
Brian
On Nov 18, 8:51am, Michael Coleman wrote:
> Subject: info-performer: Will Performer 2.2 support OpenGL shadowing?
> I hope this isn't in the digest somewhere, but we need to do multi-pass
> shadowing using Performer on an iR. I know the shadow.C sample code
> only works on IrisGL machines. Will there be OpenGL shadow code with
> Performer 2.2?
>
> Thanks in advance.
> Michael Coleman
>
> mcoleman++at++swri.edu
> mcoleman++at++txdirect.net
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>-- End of excerpt from Michael Coleman
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