[Mesa-dev] Gallium depth clamp support
Roland Scheidegger
sroland at vmware.com
Wed Jul 21 15:17:37 PDT 2010
Marek Olšák wrote:
> Hi,
>
> there is a new branch gallium-depth-clamp in the main repository which
> implements ARB_depth_clamp in Gallium. Wine uses this extension to
> disable clipping when it's requested from a D3D9 app, so it's an
> important one.
>
> There is a new state "depth_clamp" in pipe_clip_state, and a new cap
> PIPE_CAP_DEPTH_CLAMP. If you think this feature should be mandatory in
> Gallium instead, it's ok with me. There are several reasons I put the
> enable bit in pipe_clip_state, but the most important one is that Z
> clipping must be disabled in hardware first for it to work. It also
> implements depth_clamp handling in cso_cache and wires up
> ARB_depth_clamp in st/mesa.
>
> The support in Draw has also been implemented, and both softpipe and
> llvmpipe pass piglit/depth_clamp and piglit/depth-clamp-range.
>
> http://cgit.freedesktop.org/mesa/mesa/log/?h=gallium-depth-clamp
One thing I was wondering does it actually make sense to call it depth
clamp? I think d3d10 name for once (which calls this functionality depth
clip though of course this means enable/disable is reversed) makes more
sense - this disables near/far plane clipping, hence the necessity to
clamp to 0/1.
I guess having this in clip state is ok - d3d10 puts depth clip into
rasterizer state, but then again d3d10 doesn't have any clip state...
Roland
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