[Mesa-dev] [PATCH 09/11] tgsi: remove culldist semantic.

[Roland Scheidegger]

Am 14.05.2016 um 14:55 schrieb Marek Olšák:
> Dave,
> It should be noted that clip distances can be disabled by
> pipe_rasterizer_state::clip_plane_enable, but cull distances can't.
> (same as GL)

That only applies to user clip planes, not shader clip distances.


> 
> Roland,
> Our hardware only has 2 vec4 outputs. Each component can be configured
> to be "clip distance", "cull distance", or "disabled" independently.
> 

Ok.

Roland
> 
> On Sat, May 14, 2016 at 12:43 AM, Roland Scheidegger <sroland at vmware.com> wrote:
>> Am 13.05.2016 um 23:10 schrieb Dave Airlie:
>>> From: Dave Airlie <airlied at redhat.com>
>>>
>>> This isn't used anymore in the tree, culldist's
>>> are part of the clipdist semantic, we could in theory
>>> rename it, but I'm not sure there is much point, and
>>> I'd have to be careful with virgl.
>>>
>>> Signed-off-by: Dave Airlie <airlied at redhat.com>
>>> ---
>>>  src/gallium/auxiliary/tgsi/tgsi_strings.c  |  1 -
>>>  src/gallium/docs/source/tgsi.rst           | 22 ++++++++++++++++++----
>>>  src/gallium/include/pipe/p_shader_tokens.h |  1 -
>>>  3 files changed, 18 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/src/gallium/auxiliary/tgsi/tgsi_strings.c b/src/gallium/auxiliary/tgsi/tgsi_strings.c
>>> index 306ab4f..c13f7ea 100644
>>> --- a/src/gallium/auxiliary/tgsi/tgsi_strings.c
>>> +++ b/src/gallium/auxiliary/tgsi/tgsi_strings.c
>>> @@ -85,7 +85,6 @@ const char *tgsi_semantic_names[TGSI_SEMANTIC_COUNT] =
>>>     "PCOORD",
>>>     "VIEWPORT_INDEX",
>>>     "LAYER",
>>> -   "CULLDIST",
>>>     "SAMPLEID",
>>>     "SAMPLEPOS",
>>>     "SAMPLEMASK",
>>> diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
>>> index 4315707..ab12490 100644
>>> --- a/src/gallium/docs/source/tgsi.rst
>>> +++ b/src/gallium/docs/source/tgsi.rst
>>> @@ -2876,18 +2876,32 @@ annotated with those semantics.
>>>  TGSI_SEMANTIC_CLIPDIST
>>>  """"""""""""""""""""""
>>>
>>> +Note this covers clipping and culling distances.
>>> +
>>>  When components of vertex elements are identified this way, these
>>>  values are each assumed to be a float32 signed distance to a plane.
>>> +
>>> +For clip distances:
>>>  Primitive setup only invokes rasterization on pixels for which
>>> -the interpolated plane distances are >= 0. Multiple clip planes
>>> -can be implemented simultaneously, by annotating multiple
>>> -components of one or more vertex elements with the above specified
>>> -semantic. The limits on both clip and cull distances are bound
>>> +the interpolated plane distances are >= 0.
>>> +
>>> +For cull distances:
>>> +Primitives will be completely discarded if the plane distance
>>> +for all of the vertices in the primitive are < 0.
>>> +If a vertex has a cull distance of NaN, that vertex counts as "out"
>>> +(as if its < 0);
>>> +
>>> +Multiple clip/cull planes can be implemented simultaneously, by
>>> +annotating multiple components of one or more vertex elements with
>>> +the above specified semantic.
>>> +The limits on both clip and cull distances are bound
>>>  by the PIPE_MAX_CLIP_OR_CULL_DISTANCE_COUNT define which defines
>>>  the maximum number of components that can be used to hold the
>>>  distances and by the PIPE_MAX_CLIP_OR_CULL_DISTANCE_ELEMENT_COUNT
>>>  which specifies the maximum number of registers which can be
>>>  annotated with those semantics.
>>> +The properties NUM_CLIPDIST_ENABLED and NUM_CULLDIST_ENABLED
>>> +are used to divide up the 2 x vec4 space between clipping and culling.
>> This should really say how it's determined which one is which (so clip
>> dists come first).
>>
>>
>> You should remove the TGSI_SEMANTIC_CULLDIST section.
>>
>> For patch 10, shouldn't this work with softpipe too?
>>
>> Honestly, I'm not a big fan of packed clip and cull dists in the same
>> regs (it's still not the same as what d3d10 does in any case), my
>> opinion is since we generally don't allow different semantics within the
>> same reg, I see no good reason why we allow it here (and clip dists and
>> cull dists, albeit somewhat similar, are still different). So, if some
>> drivers wanted it in different regs and some in the same regs, I'd
>> prefer it to be different regs in the interface, with drivers having to
>> merge it when required, just because it looks cleaner. But if really all
>> hw wants it like that, 6,8-11 are
>> Reviewed-by: Roland Scheidegger <sroland at vmware.com>
>> (But I'd like to hear from other driver's authors.)
>>
>> Roland
>>
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