[Mesa-dev] Gallium depth clamp support

[Marek Olšák]

On Thu, Jul 22, 2010 at 12:17 AM, Roland Scheidegger <sroland at vmware.com>wrote:

> 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...
>

Depth clip does sound better to me, but honestly I don't care how we call
it. If you like the D3D naming, so be it.

-Marek
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