Your understanding is correct. I misunderstood CSAA. So it looks like that CSAA is more useless than I thought. You get the coverage-samples level of quality for back-to-front rendering, but you may get the depth-samples level of quality for front-to-back rendering, because "edges" generated by depth test failures have the same quality as the number of depth samples (if depth values are uncompressed). AMD supports that mode too, but I don't recommend using it because of the possible decrease in front-to-back rendering quality.
The way the CAP is defined doesn't actually allow NV's implementation of CSAA. A new CAP would be needed. We'll add a new GL extension for advanced MSAA. The NV extension is unusable, because it changes GL behavior in a non-backward-compatible way by allowing storage_samples = 2 for all renderbuffers (which is cheating, but not surprising from NV). Marek On Mon, May 21, 2018 at 12:55 PM, Axel Davy <davyax...@gmail.com> wrote: > Hi, > > I get the impression when looking at online documentation about EQAA and > CSAA, like > http://www.nvidia.fr/object/coverage-sampled-aa.html > > that the number of stored samples is the same for the color and depth > buffers. > Only the samples used for coverage is greater. > > With your proposal, isn't the number of samples stored in the depth buffer > always the same than the number of samples used for coverage ? > That reduces the use-cases. In nine, we have to enforce the number of > stored samples to be the same for the color and the depth buffer, but we > could increase the number of samples used for coverage and enable EQAA/CSAA > (in fact there is a similar way to advertise the feature for Nvidia and > Amd). > > But maybe I misunderstood. > > Yours, > > Axel Davy > > > On 18/05/2018 06:05, Marek Olšák wrote: > >> From: Marek Olšák <marek.ol...@amd.com> >> >> The interface only uses general MSAA terms, so it's "advanced MSAA" and >> not >> something vendor-specific. >> >> It's a proper subset of EQAA, and a proper superset of CSAA, so it's >> neither. >> >> Changes: >> - pipe_resource is changed >> - is_format_supported is changed >> - a new CAP is added >> --- >> src/gallium/docs/source/screen.rst | 31 ++++++++++++++++++++++++++-- >> src/gallium/include/pipe/p_defines.h | 1 + >> src/gallium/include/pipe/p_screen.h | 1 + >> src/gallium/include/pipe/p_state.h | 18 +++++++++++++--- >> 4 files changed, 46 insertions(+), 5 deletions(-) >> >> diff --git a/src/gallium/docs/source/screen.rst >> b/src/gallium/docs/source/screen.rst >> index 5bc6ee99f08..cf4787a1c49 100644 >> --- a/src/gallium/docs/source/screen.rst >> +++ b/src/gallium/docs/source/screen.rst >> @@ -398,20 +398,25 @@ The integer capabilities: >> * ``PIPE_CAP_LOAD_CONSTBUF``: True if the driver supports >> TGSI_OPCODE_LOAD use >> with constant buffers. >> * ``PIPE_CAP_TGSI_ANY_REG_AS_ADDRESS``: Any TGSI register can be used >> as >> an address for indirect register indexing. >> * ``PIPE_CAP_TILE_RASTER_ORDER``: Whether the driver supports >> GL_MESA_tile_raster_order, using the tile_raster_order_* fields in >> pipe_rasterizer_state. >> * ``PIPE_CAP_MAX_COMBINED_SHADER_OUTPUT_RESOURCES``: Limit on combined >> shader >> output resources (images + buffers + fragment outputs). If 0 the state >> tracker works it out. >> +* ``PIPE_CAP_FRAMEBUFFER_MIXED_SAMPLES``: Framebuffer attachments can >> have >> + different number of samples each with the following restriction: >> + color.nr_samples >= zs.nr_samples >= color.nr_storage_samples >> + If 0 is returned, the following restriction applies: >> + color.nr_samples == zs.nr_samples >= color.nr_storage_samples >> * ``PIPE_CAP_SIGNED_VERTEX_BUFFER_OFFSET``: >> Whether pipe_vertex_buffer::buffer_offset is treated as signed. The >> u_vbuf >> module needs this for optimal performance in workstation applications. >> * ``PIPE_CAP_CONTEXT_PRIORITY_MASK``: For drivers that support >> per-context >> priorities, this returns a bitmask of PIPE_CONTEXT_PRIORITY_x for the >> supported priority levels. A driver that does not support prioritized >> contexts can return 0. >> * ``PIPE_CAP_FENCE_SIGNAL``: True if the driver supports signaling >> semaphores >> using fence_server_signal(). >> * ``PIPE_CAP_CONSTBUF0_FLAGS``: The bits of pipe_resource::flags that >> must be >> @@ -718,20 +723,23 @@ is_format_supported >> Determine if a resource in the given format can be used in a specific >> manner. >> **format** the resource format >> **target** one of the PIPE_TEXTURE_x flags >> **sample_count** the number of samples. 0 and 1 mean no multisampling, >> the maximum allowed legal value is 32. >> +**storage_sample_count** the number of storage samples. This must be <= >> +sample_count. See the documentation of ``pipe_resource::nr_storage_sa >> mples``. >> + >> **bindings** is a bitmask of :ref:`PIPE_BIND` flags. >> Returns TRUE if all usages can be satisfied. >> can_create_resource >> ^^^^^^^^^^^^^^^^^^^ >> Check if a resource can actually be created (but don't actually >> allocate any >> memory). This is used to implement OpenGL's proxy textures. >> Typically, a >> @@ -761,22 +769,41 @@ Modern APIs allow using buffers as shader resources. >> (1 for 1D or 1D array textures). >> **depth0** the depth of the base mip level of the texture >> (1 for everything else). >> **array_size** the array size for 1D and 2D array textures. >> For cube maps this must be 6, for other textures 1. >> **last_level** the last mip map level present. >> -**nr_samples** the nr of msaa samples. 0 (or 1) specifies a resource >> -which isn't multisampled. >> +**nr_samples**: Number of samples determining quality, driving the >> rasterizer, >> +shading, and framebuffer. It is the number of samples seen by the whole >> +graphics pipeline. 0 and 1 specify a resource which isn't multisampled. >> + >> +**nr_storage_samples**: Only color buffers can set this lower than >> nr_samples. >> +Multiple samples within a pixel can have the same color. >> ``nr_storage_samples`` >> +determines how many slots for different colors there are per pixel. >> +If there are not enough slots to store all sample colors, some samples >> will >> +have an undefined color (called "undefined samples"). >> + >> +The resolve blit behavior is driver-specific, but can be one of these >> two: >> +1. Only defined samples will be averaged. Undefined samples will be >> ignored. >> +2. Undefined samples will be approximated by looking at surrounding >> defined >> + samples (even in different pixels). >> + >> +Blits and MSAA texturing: If the sample being fetched is undefined, one >> of >> +the defined samples is returned instead. >> + >> +Sample shading (``set_min_samples``) will operate at a sample frequency >> that >> +is at most ``nr_storage_samples``. Greater ``min_samples`` values will be >> +replaced by ``nr_storage_samples``. >> **usage** one of the :ref:`PIPE_USAGE` flags. >> **bind** bitmask of the :ref:`PIPE_BIND` flags. >> **flags** bitmask of PIPE_RESOURCE_FLAG flags. >> resource_changed >> diff --git a/src/gallium/include/pipe/p_defines.h >> b/src/gallium/include/pipe/p_defines.h >> index 6b2f33b9e37..5693396c9e9 100644 >> --- a/src/gallium/include/pipe/p_defines.h >> +++ b/src/gallium/include/pipe/p_defines.h >> @@ -794,20 +794,21 @@ enum pipe_cap >> PIPE_CAP_ALLOW_MAPPED_BUFFERS_DURING_EXECUTION, >> PIPE_CAP_POST_DEPTH_COVERAGE, >> PIPE_CAP_BINDLESS_TEXTURE, >> PIPE_CAP_NIR_SAMPLERS_AS_DEREF, >> PIPE_CAP_QUERY_SO_OVERFLOW, >> PIPE_CAP_MEMOBJ, >> PIPE_CAP_LOAD_CONSTBUF, >> PIPE_CAP_TGSI_ANY_REG_AS_ADDRESS, >> PIPE_CAP_TILE_RASTER_ORDER, >> PIPE_CAP_MAX_COMBINED_SHADER_OUTPUT_RESOURCES, >> + PIPE_CAP_FRAMEBUFFER_MIXED_SAMPLES, >> PIPE_CAP_SIGNED_VERTEX_BUFFER_OFFSET, >> PIPE_CAP_CONTEXT_PRIORITY_MASK, >> PIPE_CAP_FENCE_SIGNAL, >> PIPE_CAP_CONSTBUF0_FLAGS, >> PIPE_CAP_PACKED_UNIFORMS, >> PIPE_CAP_CONSERVATIVE_RASTER_POST_SNAP_TRIANGLES, >> PIPE_CAP_CONSERVATIVE_RASTER_POST_SNAP_POINTS_LINES, >> PIPE_CAP_CONSERVATIVE_RASTER_PRE_SNAP_TRIANGLES, >> PIPE_CAP_CONSERVATIVE_RASTER_PRE_SNAP_POINTS_LINES, >> PIPE_CAP_MAX_CONSERVATIVE_RASTER_SUBPIXEL_PRECISION_BIAS, >> diff --git a/src/gallium/include/pipe/p_screen.h >> b/src/gallium/include/pipe/p_screen.h >> index 101e229088b..94c61dfab2e 100644 >> --- a/src/gallium/include/pipe/p_screen.h >> +++ b/src/gallium/include/pipe/p_screen.h >> @@ -150,20 +150,21 @@ struct pipe_screen { >> /** >> * Check if the given pipe_format is supported as a texture or >> * drawing surface. >> * \param bindings bitmask of PIPE_BIND_* >> */ >> boolean (*is_format_supported)( struct pipe_screen *, >> enum pipe_format format, >> enum pipe_texture_target target, >> unsigned sample_count, >> + unsigned storage_sample_count, >> unsigned bindings ); >> /** >> * Check if the given pipe_format is supported as output for this >> codec/profile. >> * \param profile profile to check, may also be >> PIPE_VIDEO_PROFILE_UNKNOWN >> */ >> boolean (*is_video_format_supported)( struct pipe_screen *, >> enum pipe_format format, >> enum pipe_video_profile >> profile, >> enum pipe_video_entrypoint >> entrypoint ); >> diff --git a/src/gallium/include/pipe/p_state.h >> b/src/gallium/include/pipe/p_state.h >> index db9fa1a8e9f..1baa497b227 100644 >> --- a/src/gallium/include/pipe/p_state.h >> +++ b/src/gallium/include/pipe/p_state.h >> @@ -511,41 +511,53 @@ struct pipe_box >> int16_t depth; >> }; >> /** >> * A memory object/resource such as a vertex buffer or texture. >> */ >> struct pipe_resource >> { >> struct pipe_reference reference; >> - struct pipe_screen *screen; /**< screen that this texture belongs to >> */ >> unsigned width0; /**< Used by both buffers and textures. */ >> uint16_t height0; /* Textures: The maximum height/depth/array_size >> is 16k. */ >> uint16_t depth0; >> uint16_t array_size; >> enum pipe_format format:16; /**< PIPE_FORMAT_x */ >> enum pipe_texture_target target:8; /**< PIPE_TEXTURE_x */ >> unsigned last_level:8; /**< Index of last mipmap level >> present/defined */ >> - unsigned nr_samples:8; /**< for multisampled surfaces, nr of >> samples */ >> - unsigned usage:8; /**< PIPE_USAGE_x (not a bitmask) */ >> + /** Number of samples determining quality, driving rasterizer, >> shading, >> + * and framebuffer. >> + */ >> + unsigned nr_samples:8; >> + >> + /** Multiple samples within a pixel can have the same value. >> + * nr_storage_samples determines how many slots for different values >> + * there are per pixel. Only color buffers can set this lower than >> + * nr_samples. >> + */ >> + unsigned nr_storage_samples:8; >> + >> + unsigned usage:8; /**< PIPE_USAGE_x (not a bitmask) */ >> unsigned bind; /**< bitmask of PIPE_BIND_x */ >> unsigned flags; /**< bitmask of PIPE_RESOURCE_FLAG_x */ >> /** >> * For planar images, ie. YUV EGLImage external, etc, pointer to the >> * next plane. >> */ >> struct pipe_resource *next; >> + /* The screen pointer should be last for optimal structure packing. */ >> + struct pipe_screen *screen; /**< screen that this texture belongs to >> */ >> }; >> /** >> * Transfer object. For data transfer to/from a resource. >> */ >> struct pipe_transfer >> { >> struct pipe_resource *resource; /**< resource to transfer to/from */ >> unsigned level; /**< texture mipmap level */ >> > > >
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