[Mesa-dev] [PATCH v2 2/5] gallium: Add new PIPE_CAP_MULTISAMPLED_RENDER_TO_TEXTURE

[Kristian Høgsberg]

On Tue, Nov 6, 2018 at 6:26 PM Roland Scheidegger <sroland at vmware.com> wrote:
>
> Am 07.11.18 um 00:03 schrieb Kristian Høgsberg:
> > On Tue, Nov 6, 2018 at 2:44 PM Axel Davy <davyaxel0 at gmail.com> wrote:
> >>
> >> Hi,
> >>
> >> Is there anything to be done in the nine state trackers (or other state
> >> trackers).
> >>
> >> Nine uses create_surface. Should it expect the field to be filled
> >> properly by the driver ?
> >
> > Nothing is required from any state tracker, but if your API has an
> > extension like EXT_multisampled_render_to_texture, and the driver has
> > this new capability, you can set pipe_surface::nr_samples. The driver
> > will then render with that many samples internally and transparently
> > resolve the rendering to the (non-MSAA) resource.
> >
> >> On 06/11/2018 23:09, Kristian H. Kristensen wrote:
> >>> +   /**
> >>> +    * If a driver doesn't advertise PIPE_CAP_MULTISAMPLED_RENDER_TO_TEXTURE,
> >>> +    * pipe_surface::nr_samples will always be 0.
> >>> +    */
> >> The above comment should be added to the comment below.
> >>> +   /** Number of samples for the surface.  This can be different from the
> >>> +    * resource nr_samples when the resource is bound using
> >>> +    * FramebufferTexture2DMultisampleEXT.
> >>> +    */
> >>> +   unsigned nr_samples:8;
> >
> > Hm, I probably need to reword that a bit, since it implies the surface
> > sample count can be same as the resource, when it is only ever either
> > surface samples = 0 or surface samples > 1 with resource samples = 1.
> Wouldn't it be more logical if you rather adjust the code to match the
> comment? That is, the surface would inherit the sample count of the
> resource by default, but can be set to something different for this
> extension.

Yeah, that should work. I wanted to avoid rewriting every gallium
driver to look at surf->nr_samples instead of
surf->texture->nr_samples, but since they're the same without the new
cap, that shouldn't be necessary.

>
> > Kristian
> >
> >>> +
> >>>      union pipe_surface_desc u;
> >>>   };
> >>>
> >>
> >>
> >> Yours,
> >>
> >>
> >> Axel Davy
> >>
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