Re: Tag clear on iR ?

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Remi Arnaud (remi++at++remi.asd.sgi.com)
Fri, 18 Oct 1996 11:56:48 -0700

On Oct 18, 11:11am, Gilles Reymond wrote:
> Subject: Tag clear on iR ?
> Hi,
>
> I am investigating on the performance of the different screen clear modes
> provided by Performer 2.1 on an Infinite Reality (with iR-specific patch 1355
> installed). Two questions :
> - is z-buffer "tag" clear mode still supported or even relevant on this
> platform ? Using perfly, the PFES_TAG option does not appear on the GUI.

 As the man pages says:
 NOTES
     PFCL_MSDEPTH is only available on RealityEngine systems, and then only in
     the multisample antialiasing mode.

> - when using pfESky mode PFES_SKY, what is actually being done on the
> lower part of the horizon? According to the man pages, nothing. But
obviously,
> some resetting of the z-buffer is done, since any moving objet within this
zone
> is acually drawn properly...

 The earth/sky force the writting of Z into the z-buffer, initializing it.

>
> In any case, what is _really_ the best performance solution when it comes to
> clearing the screen on an iR ?

 It is best to force the Z-buffer [glDepthFunc(GL_ALWAYS)], and write a full
screen background 3d mesh, or a full screen 2d polygon at Zmax.
 You can keep the call to tag clear, so your application will do the right
thing on IR and on RE2.

 -- Remi

-- 




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