[Mesa-dev] Gallium depth clamp support

[Roland Scheidegger]

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