[4/22] WineD3D: A shader backend descriptor for the ati fragment shader backend

[H. Verbeet]

On 17/03/2008, Stefan Dösinger <stefan at codeweavers.com> wrote:
> Am Montag, 17. März 2008 10:01:30 schrieb H. Verbeet:
>
> > Also, all the cards that are powerful enough to support a shader
>  > implementation of fixed function processing support GLSL vertex and
>  > fragment shaders, so realistically all you really need is a GLSL ffp
>  > replacement.
>
> That's not quite true, my atifs replacement supports everything on the
>  fragment side, and that card doesn't support GLSL(not even ARBfp).
Sure, but in that aspect it isn't really different from register combiners.

>  Also on
>  the vertex side there are cards that have ARB only and not GLSL. I don't yet
>  know if we can replace the fixed function vertex pipeline on r200 cards, as
>  the 128 shader constants seem rather limiting, especially when it comes to
>  indexed vertex blending. However, it should be able to do non-indexed vertex
>  blending just fine, and we can get rid of the color conversion.
>
I think a useful ffp replacement should at least replace the vertex
processing part. Extension s like ATI_fragment_shader and
NV_register_combiners, etc. can already support pretty much all of
fixed function fragment processing without having to integrate it in
the shader backends.

In terms of replacing vertex processing, anything that still has
dedicated hardware for fixed function processing isn't really powerful
enough to run such an ffp replacement, either because of instruction
count / number of constant limitations or simply execution speed. For
nvidia hardware that basically means you'll need at least something
like a GF5 or GF6.