Le Mon, 01 Jun 2009 10:46:45 -0700
Corbin Simpson <[email protected]> a écrit:

> Patrice Mandin wrote:
> > Le Mon, 01 Jun 2009 03:24:39 +0200
> > Roland Scheidegger <[email protected]> a écrit:
> > 
> >> Yes, seems so. In fact if you take a newer spec it'll list
> >> BlendEquationSeparate as promoted to core in 2.0.
> >>
> >>> Ah OK. Then I think I should write some test for renouveau, so I check
> >>> what Nvidia do when using these functions on nv30.
> >> AFAIK Nvidia did BlendFuncSeparate in software for nv20/25 so I'd guess
> >> it could be the same for BlendEquationSeparate for nv30. Though maybe
> >> the chip is flexible enough somehow to not require this.
> > 
> > Well, from the simple renouveau test we currently have, a fragment
> > program is used on nv30 for this function, so currently no change is
> > required in Mesa. However nv30 gallium backend should be modified to
> > take this into account.
> 
> If there are other chipsets that cannot do true separate alpha blend, we 
> can always use PIPE_CAP to let Mesa know, and Mesa can do the fragment 
> program alteration itself. (r3xx and r4xx also have this, so it might be 
> useful later on.)

I did more tests. I think I was wrong, in fact, when using
BlendEquationSeparate functions, no triangle rendering command is sent
to the gpu, so I suppose it's all software rendering. The shader
program is a single instruction to set current color, plus it resend
all tcl engine state.

But it's good news if a fragment program can do this instead, so adding
the PIPE_CAP should be useful, if other cards need it also.

-- 
Patrice Mandin
WWW: http://pmandin.atari.org/
Programmeur Linux, Atari
Spécialité: Développement, jeux



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