From: Dirk Reiners (reiners++at++igd.fhg.de)
Date: 01/05/2001 02:35:42
On Jan 4, 12:41pm, Larry E. Ramey wrote:
> Subject: Crazy Image Question
>
> I suspect this is impossible as I want to do it, but I'll give it a
> swing anyway.
>
> Imagine two windows. 4 viewports. (OK, It's a CAVE)
>
> I know how to take a dump from the walls of the cave (since they are
> simply the framebuffer)
>
> What if I want a rgb file that is NOT co-planer with the FrameBuffer?
>
> Is there some way to use the texture matrix to fool the computer into
> thinking that mp=fn? I mean apply a reverse projection of something, so
> the plane that I wish to make an image of, is magically lined up with
> the framebuffer?
>
>-- End of excerpt from Larry E. Ramey
I don't think you can do it without a separate rendering pass.
Either you have to set up a separate mono viewport just for the grab, draw
the scene into it, grab it and delete/inactivate the viewport (or channel
in Perf parlance).
Alternatively you can grab the 4 walls into textures, map them onto a cube
and draw that instead of the whole scene, but you still need the separate
rendering pass.
Which one performs better is going to depend on your scene size. Texture
grabs are not the fastest possible operation, so I'd guess for most scenes
that can comfortably be rendered in a 2 pipe/4 wall CAVE just rendering
the scene again will be faster.
If you really can't do the separate rendering you could do the second
version by hand, but writing that is going to be a lot of work and pretty
slow for larger than stamp images. I guess you want to integrate that into
the CAVElib, which might make alternative 1 difficult, but 2 shouldn't be
a big problem.
Hope it helps
Dirk
-- -- -- Dirk Reiners reiners++at++igd.fhg.de, Dirk.Reiners++at++gmx.net -- OpenSG Forum http://www.opensg.org -- Rundeturmstrasse 6 http://www.igd.fhg.de/~reiners -- D-64283 Darmstadt All standard disclaimers apply. -- Truth is stranger than fiction because fiction has to make sense.
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