[Mesa-dev] gallium and ARB_texture_query_levels

[Roland Scheidegger]

Am 24.02.2014 09:38, schrieb Dave Airlie:
> I've taken a quick look at ARB_texture_query_levels,
> 
> and the HW generally seems to implement this by returning it in the W
> channel of RESINFO, which would map to the TXQ instruction,
> 
> So my initial implementation added a LEVQ TGSI instruction but I do
> think this isn't representative of the hw and I should add it to TXQ
> with maybe a CAP to say it supports levels.
> 
> Dave.
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Doing this with TXQ sounds right to me. I'm not sure you even need a cap
bit - this is typically dx10 hw which can do resinfo and dx10 is the
reason all hw returns number of levels in the w channel anyway.
Though it's possible there's some newer non-desktop hw out there not
concerned about d3d (but OpenGL ES instead) which can't do it, so a cap
is fine too.
llvmpipe actually right now will only return this in the w channel for
sviewinfo, not txq, but it could be changed. I think as long as you give
it the right write mask it should be able to drop all the extra unneeded
calculations. Though obviously for llvmpipe/softpipe it can be
implemented easily either way.

Roland