[Mesa-dev] S2TC - yet another attempt to solve the "S3TC issue"

[Corbin Simpson]

It is not transparent if applications must opt into using it.

Please go ask distributions to pick this up; we aren't going to do it
without the legal issues being cleared up.

Sending from a mobile, pardon my terseness. ~ C.
On Aug 8, 2011 6:12 AM, "Rudolf Polzer" <divverent at xonotic.org> wrote:
> On Mon, Aug 08, 2011 at 05:49:09AM -0700, Jose Fonseca wrote:
>> ----- Original Message -----
>> > The suggestion however is to include a S2TC-like method with Mesa, to
>> > basically
>> > make sure that in the long run NO distro has no support for S3TC
>> > uploading,
>> > without requiring an extra decision in each distro.
>>
>> I wouldn't oppose bundling S2TC for software renderers, but enabling S3TC
decompression on hardware is an orthogonal matter, which depends on the
licensing terms between the IHV and S3.
>>
>> If you wanna fix this, convince IHVs to fully license the S3TC use in
their hardware for Linux. So far the only IHV that _seems_ to have such wide
cross-OS license is NVIDIA.
>>
>> I think it would be good to add a FAQ about this in the docs. But I'm
done with this stupid thread. I'll enjoy my vacation and stop wasting time
with this nonsense.
>
> In other words: you want the EXISTING support in Mesa to upload S3TC
compressed
> textures (pre-compressed, not runtime compressed) to the hardware removed.
>
> It is the driconf option "Enable S3TC texture compression even if software
> support is not available" ("force_s3tc_enable" in the configuration file
or
> environment).
>
> There is already existing games that use this method to silently enable
> precompressed texture even when no libtxc_dxtn library is available:
>
> http://trac.wildfiregames.com/ticket/575
>
> So effectively, Mesa already does this. If you were right with your
opinion,
> this would mean Mesa is ALREADY violating the patent, because any game can
> set that environment variable and thus TRANSPARENTLY use S3TC, without the
> user being aware that the patented technology is being used. And then I
would
> ask how it is any MORE illegal if a distro bundles the S2TC lib, and thus
> S3TC upload is available WITHOUT setting force_s3tc_enable.
>
> Summarizing: in the EXISTING code, it's already possible for any
application to
> enable S3TC decompression. Just enable force_s3tc_enable before
initializing
> OpenGL. So it is available, just by a "different API" than the one in the
> OpenGL extension spec (due to an extra putenv() call being required).
Including
> S2TC, and thus enabling compressed texture upload by default, only changes
the
> API by which this functionality is enabled to the standard OpenGL one
(without
> the putenv() call).
>
> Best regards,
>
> Rudolf Polzer
> _______________________________________________
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> mesa-dev at lists.freedesktop.org
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