[Mesa-dev] [PATCH 3/3] mesa/st: implement ARB_stencil_texturing

[Ilia Mirkin]

On Sun, May 4, 2014 at 11:59 AM, Roland Scheidegger <sroland at vmware.com> wrote:
> Am 03.05.2014 11:25, schrieb Ilia Mirkin:
>> If StencilSampling is enabled on the texture object, pass in an
>> equivalent stencil-only format.
>>
>> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
>> ---
>>
>> This replaces my earlier series, based on a suggestion from Michel Dänzer on
>> IRC. Much simpler, and enables it for pretty much all gallium drivers.
>>
>>  src/mesa/state_tracker/st_atom_texture.c | 4 ++++
>>  src/mesa/state_tracker/st_extensions.c   | 5 +++++
>>  2 files changed, 9 insertions(+)
>>
>> diff --git a/src/mesa/state_tracker/st_atom_texture.c b/src/mesa/state_tracker/st_atom_texture.c
>> index afc6d9d..928a4ff 100644
>> --- a/src/mesa/state_tracker/st_atom_texture.c
>> +++ b/src/mesa/state_tracker/st_atom_texture.c
>> @@ -271,6 +271,10 @@ st_get_texture_sampler_view_from_stobj(struct st_context *st,
>>
>>     sv = st_texture_get_sampler_view(st, stObj);
>>
>> +   if (stObj->base.StencilSampling &&
>> +       util_format_is_depth_and_stencil(format))
>> +      format = util_format_stencil_only(format);
>> +
>>     /* if sampler view has changed dereference it */
>>     if (*sv) {
>>        if (check_sampler_swizzle(stObj, *sv) ||
>> diff --git a/src/mesa/state_tracker/st_extensions.c b/src/mesa/state_tracker/st_extensions.c
>> index 33cd129..12ba82d 100644
>> --- a/src/mesa/state_tracker/st_extensions.c
>> +++ b/src/mesa/state_tracker/st_extensions.c
>> @@ -507,6 +507,11 @@ void st_init_extensions(struct st_context *st)
>>
>>        { { o(OES_compressed_ETC1_RGB8_texture) },
>>          { PIPE_FORMAT_ETC1_RGB8 } },
>> +
>> +      { { o(ARB_stencil_texturing) },
>> +        { PIPE_FORMAT_X24S8_UINT,
>> +          PIPE_FORMAT_S8X24_UINT },
>> +        GL_TRUE }, /* at least one format must be supported */
>>     };
>>
>>     /* Required: vertex fetch support. */
>>
>
> This version looks good to me. I guess you had to support stencil
> texturing for all depthstencil formats the driver claims to support, but
> presumably this isn't a problem for any hardware which can do it in the
> first place.

At a quick glance at a few drivers I didn't notice any problems.
Should any issues come up, we can do something cleverer, like checking
directly that for each supported DEPTH_STENCIL format, that its
related STENCIL format is also supported. It didn't seem that the
complexity was worth it for now.

> (Gallium actually is a bit lenient wrt to sampling depthstencil
> textures, if you pass in a depthstencil format it will assume you want
> the depth part - it would be cleaner if you'd have to specify the
> corresponding depth-only format in the view).

Hmm... that seems akin to poking a dragon with a stick. In theory that
seems like it should work, but I'd like to leave it to someone else to
find out :)

  -ilia