[Mesa-dev] [PATCH 2/2] gallium: Replaced gl_rasterization_rules with lower_left_origin and half_pixel_center.

[Dave Airlie]

On Sun, Apr 21, 2013 at 5:36 PM, Jose Fonseca <jfonseca at vmware.com> wrote:
> ----- Original Message -----
>> Do we really need the lower_left_origin state? I think I can't
>> implement it for radeon and it's the kind of stuff that should be
>> taken care of by the state tracker anyway.
>
> My understanding is that hardware had switches for this sort of thing. It's really hard to provide fully-conforming rasterization for opengl, dx9 & dx10 without it.
>
> If your hardware allows to put a negative pitch on rendertargets, then that should also do it.
>
> If you know what is the hardware's sub-pixel rasterization resolution, then adding a vertical bias equal to that amount, depending on this state, would give a very close approximation. (This would get the top/bottom edges right, at expense of small inaccuracies on non-horizontal edges)
>
>> Isn't it sufficient to just
>> set a viewport which is upside down, like we do now?
>
> I'm not aware of rasterization top-left rule being affected by the viewport flipping.
>
> Do both
>
>  ./bin/triangle-rasterization -auto
>  ./bin/triangle-rasterization -use_fbo -auto
>
> currently work for you?
>

just FYI, on my evergreen, the first fails the second passes, maybe
someone could try on fglrx, I'd be sorta willing to guess AMD hw just
does DX10 :)

and I think I've heard some complaints about our rendering offseting
being wrong somewhere in the past on r600.

Dave.