[Mesa-dev] [PATCH v2 2/5] gallium: Add new PIPE_CAP_MULTISAMPLED_RENDER_TO_TEXTURE

[Kristian Høgsberg]

On Fri, Nov 16, 2018 at 7:48 PM Marek Olšák <maraeo at gmail.com> wrote:
>
> I think the name PIPE_CAP_MULTISAMPLED_RENDER_TO_TEXTURE is slightly misleading, because it doesn't imply anything about the OpenGL ES behavior, which is that a texture is multisampled in the cache, but single-sampled in memory. This should be mentioned somewhere.

Not sure exactly which change you're recommending, but in retrospect,
I think it would be better to name the cap in term of how it changes
the gallium API instead of the GLES extension it enables. How about
PIPE_CAP_SURFACE_SAMPLE_COUNT, to indicate that it allows overriding
sample counts in pipe_surface?

>
> Marek
>
>
> On Tue, Nov 6, 2018 at 5:19 PM Kristian H. Kristensen <hoegsberg at gmail.com> wrote:
>>
>> This new pipe cap and the new nr_samples field in pipe_surface lets a
>> state tracker bind a render target with a different sample count than
>> the resource. This allows for implementing
>> EXT_multisampled_render_to_texture and
>> EXT_multisampled_render_to_texture2.
>>
>> Signed-off-by: Kristian H. Kristensen <hoegsberg at chromium.org>
>> ---
>>  src/gallium/auxiliary/util/u_framebuffer.c | 10 ++++++++--
>>  src/gallium/docs/source/screen.rst         |  3 +++
>>  src/gallium/include/pipe/p_defines.h       |  1 +
>>  src/gallium/include/pipe/p_state.h         |  6 ++++++
>>  4 files changed, 18 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/gallium/auxiliary/util/u_framebuffer.c b/src/gallium/auxiliary/util/u_framebuffer.c
>> index 5bafddc726f..127623a7677 100644
>> --- a/src/gallium/auxiliary/util/u_framebuffer.c
>> +++ b/src/gallium/auxiliary/util/u_framebuffer.c
>> @@ -229,13 +229,19 @@ util_framebuffer_get_num_samples(const struct pipe_framebuffer_state *fb)
>>     if (!(fb->nr_cbufs || fb->zsbuf))
>>        return MAX2(fb->samples, 1);
>>
>> +   /**
>> +    * If a driver doesn't advertise PIPE_CAP_MULTISAMPLED_RENDER_TO_TEXTURE,
>> +    * pipe_surface::nr_samples will always be 0.
>> +    */
>>     for (i = 0; i < fb->nr_cbufs; i++) {
>>        if (fb->cbufs[i]) {
>> -         return MAX2(1, fb->cbufs[i]->texture->nr_samples);
>> +         return MAX3(1, fb->cbufs[i]->texture->nr_samples,
>> +                     fb->cbufs[i]->nr_samples);
>>        }
>>     }
>>     if (fb->zsbuf) {
>> -      return MAX2(1, fb->zsbuf->texture->nr_samples);
>> +      return MAX3(1, fb->zsbuf->texture->nr_samples,
>> +                  fb->zsbuf->nr_samples);
>>     }
>>
>>     return 1;
>> diff --git a/src/gallium/docs/source/screen.rst b/src/gallium/docs/source/screen.rst
>> index 0abd164494c..2a062a7027c 100644
>> --- a/src/gallium/docs/source/screen.rst
>> +++ b/src/gallium/docs/source/screen.rst
>> @@ -477,6 +477,9 @@ subpixel precision bias in bits during conservative rasterization.
>>    0 means no limit.
>>  * ``PIPE_CAP_MAX_VERTEX_ELEMENT_SRC_OFFSET``: The maximum supported value for
>>    of pipe_vertex_element::src_offset.
>> +* ``PIPE_CAP_MULTISAMPLED_RENDER_TO_TEXTURE``: Whether the driver
>> +  supports pipe_surface overrides of resource nr_samples. If set, will
>> +  enable EXT_multisampled_render_to_texture.
>>
>>  .. _pipe_capf:
>>
>> diff --git a/src/gallium/include/pipe/p_defines.h b/src/gallium/include/pipe/p_defines.h
>> index dacedf5b936..0ecfaf3ba5e 100644
>> --- a/src/gallium/include/pipe/p_defines.h
>> +++ b/src/gallium/include/pipe/p_defines.h
>> @@ -823,6 +823,7 @@ enum pipe_cap
>>     PIPE_CAP_MAX_COMBINED_HW_ATOMIC_COUNTER_BUFFERS,
>>     PIPE_CAP_MAX_TEXTURE_UPLOAD_MEMORY_BUDGET,
>>     PIPE_CAP_MAX_VERTEX_ELEMENT_SRC_OFFSET,
>> +   PIPE_CAP_MULTISAMPLED_RENDER_TO_TEXTURE,
>>  };
>>
>>  /**
>> diff --git a/src/gallium/include/pipe/p_state.h b/src/gallium/include/pipe/p_state.h
>> index fd670345aad..89cffb15bd8 100644
>> --- a/src/gallium/include/pipe/p_state.h
>> +++ b/src/gallium/include/pipe/p_state.h
>> @@ -443,6 +443,12 @@ struct pipe_surface
>>     uint16_t width;               /**< logical width in pixels */
>>     uint16_t height;              /**< logical height in pixels */
>>
>> +   /** Number of samples for the surface.  This can be different from the
>> +    * resource nr_samples when the resource is bound using
>> +    * FramebufferTexture2DMultisampleEXT.
>> +    */
>> +   unsigned nr_samples:8;
>> +
>>     union pipe_surface_desc u;
>>  };
>>
>> --
>> 2.19.1.930.g4563a0d9d0-goog
>>
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