On Wed, Sep 14, 2016 at 1:29 PM, Anuj Phogat <anuj.pho...@gmail.com> wrote:
> On Wed, Sep 14, 2016 at 10:45 AM, Jason Ekstrand <ja...@jlekstrand.net>
> wrote:
> > From the ARB_gpu_shader5 spec:
> >
> > The built-in functions interpolateAtCentroid() and
> interpolateAtSample()
> > will sample variables as though they were declared with the "centroid"
> > or "sample" qualifiers, respectively.
> >
> > When running with persample dispatch forced by the API, we interpolate
> > anything that isn't flat as if it's qualified by "sample". In order to
> > keep interpolateAtCentroid() consistent with the "centroid" qualifier, we
> > need to make interpolateAtCentroid() do sample interpolation instead.
> > Nothing in the GLSL spec guarantees that the result of
> > interpolateAtCentroid is uniform across samples in any way, so this is a
> > perfectly fine thing to do.
> >
> This explanation sounds good to me. To be consistent with what
> we do in case of per sample interpolation, shouldn't we do sample
> interpolation in case of InterpolateAtOffset() too? This series
> doesn't seem to include it.
>
No. interpolateAtOffset ask that the input be interpolated at a particular
offset relative to the pixel center. I believe we have to respect that.
> > Fixes 8 of the new dEQP-VK.pipeline.multisample_interpolation.* Vulkan
> CTS
> > tests that specifically validate consistency between the "sample"
> qualifier
> > and interpolateAtSample()
> >
> > Signed-off-by: Jason Ekstrand <ja...@jlekstrand.net>
> > ---
> > src/mesa/drivers/dri/i965/brw_fs.cpp | 26 ++++++++++++++++++++++++++
> > 1 file changed, 26 insertions(+)
> >
> > diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp
> b/src/mesa/drivers/dri/i965/brw_fs.cpp
> > index 75642d3..9dbb699 100644
> > --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
> > +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
> > @@ -6497,6 +6497,32 @@ brw_nir_set_default_interpolation(const struct
> gen_device_info *devinfo,
> > var->data.sample = false;
> > }
> > }
> > +
> > + if (per_sample_interpolation) {
> > + nir_foreach_block(block, nir_shader_get_entrypoint(nir)) {
> > + nir_foreach_instr(instr, block) {
> > + if (instr->type != nir_instr_type_intrinsic)
> > + continue;
> > +
> > + nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
> > + if (intrin->intrinsic != nir_intrinsic_interp_var_at_
> centroid)
> > + continue;
> > +
> > + nir_variable *var = intrin->variables[0]->var;
> > + if (var->data.interpolation == INTERP_MODE_FLAT)
> > + continue;
> > +
> > + /* The description of the interpolateAtCentroid intrinsic
> is that
> > + * it interpolates the variable as if it had the "centroid"
> > + * qualifier. When executing with
> per_sample_interpolation, this
> > + * is equivalent to having the "sample" qualifier. Just
> convert
> > + * it to a load_var instead.
> > + */
> > + assert(var->data.sample);
> > + intrin->intrinsic = nir_intrinsic_load_var;
> > + }
> > + }
> > + }
> > }
> >
> > /**
> > --
> > 2.5.0.400.gff86faf
> >
> > _______________________________________________
> > mesa-dev mailing list
> > mesa-dev@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>
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