[Mesa-dev] Mesa (gallium-msaa): gallium: interface changes for multisampling

[José Fonseca]

On Mon, 2010-04-26 at 11:34 -0700, Keith Whitwell wrote:
> On Mon, 2010-04-26 at 11:27 -0700, José Fonseca wrote:
> > Hi Roland,
> > 
> > Overall looks good. It's nice to finally have a way to export MSAA
> > capabilities, and see the pipe_surfaces use being more constrained.
> > 
> > A few comments inline, but no strong feelings so feel free to do as you
> > wish.
> 
> > > diff --git a/src/gallium/include/pipe/p_screen.h b/src/gallium/include/pipe/p_screen.h
> > > index beff1ae..1bad045 100644
> > > --- a/src/gallium/include/pipe/p_screen.h
> > > +++ b/src/gallium/include/pipe/p_screen.h
> > > @@ -99,10 +99,19 @@ struct pipe_screen {
> > >     boolean (*is_format_supported)( struct pipe_screen *,
> > >                                     enum pipe_format format,
> > >                                     enum pipe_texture_target target,
> > > -                                   unsigned bindings,
> > > +                                   unsigned bindings,
> > >                                     unsigned geom_flags );
> > >
> > >     /**
> > > +    * Check if the given pipe_format is supported with a requested
> > > +    * number of samples for msaa.
> > > +    * \param sample_count number of samples for multisampling
> > > +    */
> > > +   boolean (*is_msaa_supported)( struct pipe_screen *,
> > > +                                 enum pipe_format format,
> > > +                                 unsigned sample_count );
> > 
> > Instead of a new is_msaa_support() I'd prefer see sample_count in
> > is_format_supported or better, replace both with is_resource_supported
> > which takes a resource template. But I understand that's a bit beyond
> > the scope of this change.
> 
> Is there a reason we'd need this extra flexibility, or do you just
> prefer having a single interface?  

No flexibility reason. I'd just prefer a single interface that mirrors
resource_create.

> Do we need to be able to say that we can do 8x msaa for 2d rgba8
> textures, but not cube?  Or some other combination?

No, not that I know of. I just gave a look at DirectX Caps Viewer on
NVIDIA, and the above interface seem right for D3D10. But actually for
D3D9 the ability of supporting non-masked msaa is exported seperately.

Perhaps we could have a special value for sample_count (e.g., -1) to
signify non-masked msaa.

Jose