[Mesa-dev] Anisotropic filtering in llvmpipe

[Alan Thomas]

Hi mesa-dev,

Working through a current server-side OpenGL rendering project, our team is
running into hurdles with regard to anisotropic filtering. Aniso is a hard
dependency for our rendering needs, but softpipe/swrast (which support
aniso) are too slow performance-wise. Llvmpipe doesn't currently support
anisotropic filtering, as far as I can tell.

So, we are using GPU hardware in production, which is costly and not as
portable or repeatable as a software-based renderer might be.

My question: what are the hurdles to implementing anisotropic filtering in
llvmpipe? Has there been any recent discussion about it?

I found these implementations for swrast and softpipe by Andreas Faenger in
2011:

- swrast:
https://lists.freedesktop.org/archives/mesa-commit/2011-May/030692.html
- softpipe:
https://lists.freedesktop.org/archives/mesa-commit/2011-June/030966.html

GitHub mirrors for readability:

- swrast:
https://github.com/freedreno/mesa/commit/8a98aabe0bcea42cfdc982001ae4876e3d9b1214
-
https://github.com/freedreno/mesa/commit/f4537f99cc83cb8133f66dc97c613e95dc0fe162

Could Andreas's implementation be ported to llvmpipe in a relatively
straightforward manner, or are there performance considerations in llvmpipe
that make that algorithm less than ideal? Maybe some shortcuts similar to
hardware implementations?

I've considered potentially garnering internal support to sponsor the
development financially and would also be curious if that would be welcomed
by the project (if I can get support)... and if so, if there would be any
individual who would be best suited to handle the implementation.

-- 
*Alan Thomas*
Senior Manager, Engineering

minted.
http://www.minted.com/
747 Front Street, Suite 200, San Francisco, CA 94111
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