State of Linux graphics

Ian Romanick idr at us.ibm.com
Thu Sep 1 10:21:24 PDT 2005


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Brian Paul wrote:

> It's other (non-orientation) texture state I had in mind:
> 
> - the texel format (OpenGL has over 30 possible texture formats).
> - texture size and borders
> - the filtering mode (linear, nearest, etc)
> - coordinate wrap mode (clamp, repeat, etc)
> - env/combine mode
> - multi-texture state

Which is why it's such a good target for code generation.  You'd
generate the texel fetch routine, use that to generate the wraped texel
fetch routine, use that to generate the filtered texel fetch routine,
use that to generate the env/combine routines.

Once-upon-a-time I had the first part and some of the second part
written.  Doing just that little bit was slightly faster on a Pentium 3
and slightly slower on a Pentium 4.  I suspect the problem was that I
wasn't caching the generated code smart enough, so it was it trashing
the CPU cache.  The other problem is that, in the absence of an
assembler in Mesa, it was really painful to change the code stubs.
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