[Mesa-dev] RFC: Expose vertex/fragment progam limits in Mesa state tracker

[José Fonseca]

I agree that deriving coarse grained caps from fine grained sounds
better.

Anyway, I'll apply this on until we have better caps system inplace, as
it's better than nothing.

One more question, having the design of these new fine caps in mind, are
the gl_program_constants sufficient?

  MaxNativeInstructions      
  MaxNativeAluInstructions   
  MaxNativeTexInstructions   
  MaxNativeTexIndirections   
  MaxNativeAttribs           
  MaxNativeTemps             
  MaxNativeAddressRegs       
  MaxNativeParameters  

One obvious omission relative to D3D9 caps are max dynamic control flow
depth. These are not mentioned in the R300ToDo wiki page. Does hardware
we care about has such limitations too?

Also, it's interesting to read on the R300ToDo wiki page 

  "Vertex formats GL_*INT and GL_DOUBLE are not supported. GL_*SHORT is
supported only for 2- and 4-component vertex attributes, and GL_*BYTE
only for 4-component attributes. All individual vertex attribute fetches
must be DWORD-aligned."

This clearly resembles the
http://msdn.microsoft.com/en-us/library/bb172533(VS.85).aspx . It
appears that modifying draw module or a new library for software vertex
fetch/emit without vertex shading would be useful for a lot of hardware.

Jose

On Thu, 2010-04-29 at 14:12 -0700, Marek Olšák wrote:
> I was getting at your former idea of replacing caps with feature
> levels. I was also commenting on the proposed José's patch that we
> should have fine-grained
> 
> On Thu, Apr 29, 2010 at 10:09 PM, Zack Rusin <zackr at vmware.com> wrote:
>         On Thursday 29 April 2010 15:44:35 Marek Olšák wrote:
>         > On Thu, Apr 29, 2010 at 8:30 PM, Zack Rusin
>         
>         >  <zackr at vmware.com<mailto:zackr at vmware.com>> wrote: It seems
>         like all we'd
>         
>         >  really need is relate those things to
>         > the feature/api levels it exposes and document it.
>         >
>         > Feature levels are a pretty bad match for D3D9-level
>         chipsets since the
>         >  hardware is so divergent that you'd need a lot of them.
>         You'd have at
>         >  least 2 (I can come up with 3) levels just for r300g, at
>         least two levels
>         >  for nvfx, and another two levels for the i9xx drivers,
>         provided all these
>         >  drivers want to expose precisely every feature they can
>         support. There is
>         >  a reason for having shader models sm2.0, sm2.0a, and
>         sm2.0b. Moreover this
>         >  Microsoft idea is _absolutely_ useless for a GL driver. I
>         like more the
>         >  idea of having util functions for deriving feature levels
>         from a set of
>         >  caps rather than caps from feature levels.
>         
>         
>         I'm not sure if you actually looked what Jakob committed,
>         because what you're
>         describing is what he's done. Or are you arguing against some
>         part of that
>         implementation?
> 
> I was assuming you'd wanted to return to your former idea of replacing
> caps with feature levels rather than having what Jakob has committed.
> If it's not the case then ignore my message.
> 
> Also looking at José's patch I think we should have fine-grained
> queries ideally for each shader stage separately if we want it to be
> useful at all. The proposed minimum limits are fine except that
> MaxNativeTexIndirections for ps2.0 should be 4. For an idea how the
> shader limits vary for r300g, please see the two tables at the
> beginning of this page:
> http://dri.freedesktop.org/wiki/R300ToDo

Vertex formats GL_*INT and GL_DOUBLE are not supported. GL_*SHORT is
supported only for 2- and 4-component vertex attributes, and GL_*BYTE
only for 4-component attributes. All individual vertex attribute fetches
must be DWORD-aligned.