[Mesa-dev] [PATCH v2] i965/fs: Don't use the pixel interpolater for centroid interpolation

Chris Forbes chrisf at ijw.co.nz
Mon Jul 13 09:43:03 PDT 2015

Oh, never mind - I see there's another hunk that my mailer had folded away
for some reason. I'm happy that it's correct now :)
On Jul 13, 2015 23:33, "Neil Roberts" <neil at linux.intel.com> wrote:

> Chris Forbes <chrisf at ijw.co.nz> writes:
> > Nitpicks aside, I don't think this is a great idea now that you've got
> > the SKL PI working.
> Can you explain why you don't think this is a good idea? Is it because
> it is an optimisation for something that is not known to be a big use
> case so carrying around the extra code just adds unnecessary maintenance
> burden? I could agree with that so I'm happy to abandon the patch for
> now if that's the general consensus.
> > I also think it's broken -- you need to arrange to have the centroid
> > barycentric coords delivered to the FS thread, which won't be
> > happening if this is the *only* use of them. Masked in the tests,
> > because they compare with a centroid-qualified input. [I'm assuming
> > you don't always get these delivered to the FS in SKL, but no docs
> > access...]
> The changes to brw_compute_barycentric_interp_modes in the patch ensure
> that the centroid barycentric coords are delivered whenever
> interpolateAtCentroid is used in a shader. I don't think this is a
> problem. At least it seems to work in a simple test without using a
> separate varying with the centroid qualifier.
> Regards,
> - Neil
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