Re: Performer, IR, and Double Buffering
Angus Dorbie (dorbie++at++multipass.asd.sgi.com)
Tue, 8 Jul 1997 16:10:15 -0700
On Jul 8, 9:31am, Pete Willemsen wrote:
> Subject: Performer, IR, and Double Buffering
> Greetings,
>
> In regards to double buffering on the IR, where does the memory for
> the "back" buffer come from? I've been doing some calculations
> regarding whether or not some of our desired configurations would be
> possible on our 1 RM-6. In doing this I became confused as to whether
> the memory for the "back" buffer should be included in the
> calculation.
>
> My confusion also lead me to wonder if Performer is automatically
> using double buffering. I do not recall specifying that option in our
> Performer app. I do have background in OpenGL and Inventor, both of
> which have you specify whether or not to use double buffering.
>
> Back to the calculation... In a sample configuration, if I'm using
> small pixels (256 bits) then after all the multi-samplings, RGBA, and
> Z-buffers have been accounted for, I have only used 224 bits.
>
> 2 1280 x 1024 Channels on 1 RM-6
> 4 samples of each pixel
> 10 bits/component for RGBA
> 15 bit Z-buffer
> 1 bit stencil buffer
> 4 * ( 4*10 + 15 + 1 ) = 224 bits used
> 256 - 224 = 32 bits/pixels unused
To this calculation you need to add a 8 bit per component front
and back buffer. The samples have to be summed to somewhere right.
There is no RGBA10 support, only RGBA12 and RGB10 so adjust
your sums for this also.
There's also a 32 bit word you need to add which is used for
overlay, windowing, etc.
Use glxinfo and findvis to investigate supported framebuffer formats
for a given pixel depth. It's not as simple as adding up the numbers,
the visual must be possible & supported. If you have an iR then there's
no need to guesstimate the numbers, you have answers at your fingertips.
Performer defaults to a double buffered visual.
Cheers,Angus.
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on Mon Aug 10 1998 - 17:55:35 PDT