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

Marek Olšák maraeo at gmail.com
Tue Aug 9 14:45:23 PDT 2011

On Tue, Aug 9, 2011 at 12:25 PM, Jose Fonseca <jfonseca at vmware.com> wrote:
> I don't have time for a longer reply now, but I do think your S2TC work is interesting, and that you've successfully contoured the patent claims, at least for the decompression, as I didn't look at the compression bits.
> But, there was never anything you could have done to improve the situation for GPU S3TC decompression.  It's not just a US patent system vs the rest.  It's complex, but it's all in the archives, as it has all been discussed before.

Well, actually, there is a solution. A solution which has not been
available until now.

The solution is not to use GPU S3TC decompression, obviously. Instead,
let's use GPU S2TC decompression. We have integer opcode support
coming, right? We can use those to decompress S2TC textures, which
would be loaded as integer textures. Of course, we'd have to implement
filtering as well and maintain a few shader variants in case somebody
binds an S2TC texture, so that we can switch a shader to S2TC
decompression for a particular sampler.

The only problem is S2TC can't correctly decompress every S3TC
texture, so we'd be noncompliant. Noncompliant is probably better than
not working at all. So what do you guys think?


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