[Mesa-dev] [PATCH 04/15] i965/blorp: Use MSDISPMODE_PERSAMPLE rendering when necessary

[Paul Berry]

On 21 May 2012 22:01, Olivier Galibert <galibert at pobox.com> wrote:

> On Mon, May 21, 2012 at 07:16:35PM -0700, Paul Berry wrote:
> > - Add the front-end API to allow the client to request per-sample shading
> > (I assume it's glEnable(GL_HAM_SANDWICH) or something like that, in which
> > case it should be easy)
>
> There is a "MIN_SAMPLE_SHADING" value in the [0,1] interval which is
> set by glMinSampleShading(clampf value).  It tells the minimum ratio
> of samples that must be individually shaded.  For instance, if you're
> doing 4xMSAA and mss=0.75, then you must shade at least 3 samples.
>

Thanks, Olivier, that's exactly the information I was looking for.


>
> Always shading all of them as soon as mss is non-zero is compliant to
> the spec.


Ok, cool.  I think we can improve on this slightly by doing persample
dispatch when mss >= 1/N (where N=number of samples per pixel).  Of course
in practice it's hard to see why anyone would set 0 < mss <= 1/N on purpose
:)


>  Always shading all of them all the time is actually
> compliant to the spec, as far as I can say, but would be a bad idea.
>
>  OG.
>
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