Re: Texture Paging

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Angus Dorbie (dorbie++at++sgi.com)
Wed, 03 Nov 1999 18:48:09 -0800

oops, forgot to cc everyone.

Basically the IMPACT GFX system has some page structure to TRAM which
the texture memory manager can't make 100% efficient use of under some
circumstances.

To get best memory use the pfu's to build the texture list before
download. They perform some component sorting for memory useage
efficiency on IMPACT.

Cheers,ANgus.

'Bwana' Bob Buckley wrote:
>
> Angus, hopefully, you can tell me why I'm paging textures. I'm running
> on a Octane with 4Mb of texture memory and Performer V2.2.6
>
> The database I have include two distinct pfTextures:
>
> Texture #1
> 256 X 256 X 2 = 131072 bytes
> loaded as default (2 bytes per texels)
>
> Texture #2
> 1024 X 512 X 4 = 2097152 bytes
> loaded as RGBA_8 (4 bytes per texel)
> bilinear min filter
> trilinear mip map mag filter.
> Hence, 4/3 * 2097152 = 2796203 bytes
>
> I'm running pfuDownloadTexList which confirms all but the additional
> memory required for the mip mapping.
>
> In channel #1 I load
>
> Texture #1
> Geostate #1
> texture enabled
> transparency enabled
> lighting disabled
> default texenv
>
> Texture #2
> Geostate #2
> texture enabled
> default texenv
>
> And in channel #2 I again load texture #2 but attached to a different
> geostate:
>
> Texture #2
> Geostate #3
> texture enabled
> lighting disabled
> default texenv
>
> I'm getting texture paging with avg loads equal to 1.0 and kbytes of
> 2097.152
> I watch the number of loads go from 0 to 24 then it repeats itself
> (i.e., after it loads 24 straight times it doesn't load for a single
> frame, then starts loading again).
> This repeating behavior changes when I run with breaks in cvd.
>
> Are there any blatant errors I'm making in the way in which this machine
> (or other Iris') can handle this situation? I am aware of some of the
> banking restrictions of the iRs but know little of the Octanes.
>
> If nothing is real obvious I can probably put it into a test case and
> work from there.
>
> Help!
> Thanks!

-- 
"Success is the ability to go from one failure to another with
 no loss of enthusiasm."    -    Winston Churchill.


Performer + OpenGL examples and tutors: http://www.dorbie.com/

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