Re: Texture memory corruption

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Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Thu, 10 Oct 1996 21:03:02 +0100

On Oct 10, 8:50pm, Harri Kaimio wrote:
> Subject: Texture memory corruption
> Hi all Performers!
>
> This is probably my fault, I am just asking if someone would have a
> hint...
>
> In my application I am getting my texture memory corrupted when I move
> to a different partof my scene hierarchy that has mostly different
> textures. The problem clearly has something to do with texture loading,
> since nothing weird happens if I start from the offending part of the
> scene. I am running on Hing Impact with 4TRAM, IRIX 6.2 and Performer
> 2.1.
>
> Questions:
>
> 1. Should Performer automatically unload textures from hardware tex
> memory when all geometry that uses them is out of view/removed from
> graph? I have an image billboard that changes from time to time, and
> according to Performer statistics, the system starts paging textures
> constantly after 5 or 6 texture changes (the texture is 256x256, 8 bit
> per component)

No it doesn't. It sounds like you have exceeded texture memory capacity
so it starts paging. You could try explicitly paging the texture in your
code using sub texture loads as a workaround.

You describe texture paging but you don't seem to describe any corruption.
Is your problem just paging? If so then this is some sort of texture
fragmentation problem, it's not really fair to describe this as corruption.

It is easily possible that in your case the
different download order results in less efficient memory usage.

Guy Russell has rewritten the texture list & download utility to sort textures
for efficient use on IMPACT.

>
> 2. Should Performer handle correctly situation where all textures don't
> fit in HW tex memory?

Yes, but you should really thank OpenGL for this.

>
> If you have any other ideas about what could cause texture corruption, I
> would be very happy to hear of them.

Texture memory corruption shouldn't happen.
If it does then it's most likely an OpenGL bug, check with your
local support office for the recommended patch list on IMPACT for
your OS.

>
>
> --
> -----------------------------------------------------------------
> Harri Kaimio | harri.kaimio++at++yle.fi
> Computer Graphics Specialist | http://cartes.hut.fi/~hkaimio
> Finnish Broadcasting Company | Tel. +358-40-50 67 679
> TV Production Operations | Fax. +358-0-1480 4769
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>-- End of excerpt from Harri Kaimio

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