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

[Ilia Mirkin]

On Fri, May 13, 2016 at 6:43 PM, 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.)

AFAIK all DX10+ NVIDIA, Intel, and AMD hardware wants it that way. I'm
not aware of any other hw out there that supports culling.
(Indications are that Adreno doesn't do either clipping or culling.
Not sure about the others.)

  -ilia