Re: Frambuffer configuration Onyx IR
Angus Dorbie (dorbie++at++sgi.com)
Thu, 15 Jul 1999 12:10:16 -0700
Eric Kunze wrote:
>
> > No, the problem is that when you use quad-buffer stereo, it appears to
> > me that you
> > can only use stereo channel configurations that only use 1/2 of the
> > framebuffer.
> > The other half is used by the (not seen in ircombine) second dualbuffers
> > (hence quad).
> > With old stereomode, the framebuffer is partitioned in two halfs anyway,
> > reducing the
> > actual vertical resolution.
> > Can anyone confirm that?
>
> Ircombine will report what pixel depth you get for a given framebuffer size,
> number of RMs combination. The channel configuration has nothing to do with
> the visuals available. You can get stereo visuals without having any stereo
> channels running.
>
> The visuals available are dependant only on the pixel depth. If you have a
> single RM and are doing a framebuffer of 2560x1024, you are getting small
> pixels. With small pixels, you cannot get quadbuffer stereo and multisampling
> and Z. You can get quadbuffer stereo and Z, just not multisampling. Samples
> require a lot of framebuffer memory.
>
> If you add a second RM, you can go up to medium pixel depth, which does
> allow samples, db, stereo and Z. If you bring up the "Edit Globals" button in
> ircombine, you can see what pixel depth a combination will have. You can use
> the "Edit User Defined Hardware" option to see what pixel depths various #s of
> RMs will give you. Running findvis or glxinfo -t will show you what visuals
> are currently available.
>
> > Works ok for my friends (with a 4pipe "lots of RM") too, so it should
> > work here too, the question is the following:
> > Does multisampling uses additional FB- resources that i have to keep
> > in mind when i try to configure it?
On infinite Reality should always be able to configure multisample
anti-aliasing with and framebuffer depth. But if you need multisample
AND stereo or if you need 8 sample anti-aliasing instead of 4 then I
expect you will need > small pixels.
Cheers,ANgus.
>
> Yes, multisampling uses a lot of framebuffer resources. Your friend with 4
> RMs has 4x as much framebuffer as you, that is how they manage to get the
> visuals you don't. 2RMs should be enough for what you want though.
>
> Eric
--
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on Thu Jul 15 1999 - 12:10:22 PDT