What Mesa Has Left With OpenGL 3, OpenGL 4

With the release this week of the OpenGL 4.2 specification (and accompanying GL Shading Language 4.20 revision), the TODO list for the open-source Mesa developers just got a bit longer. Mesa / Gallium3D still lacks full support for OpenGL 3.0 and all of the revisions since that 2008 specification release.

The OpenGL 3.0 support in this open-source OpenGL library is slowly coming together (see the many Phoronix articles), but the GL Shading Language 1.30 support is incomplete along with other key areas. Some of the functionality is also limited "out of the box" due to patent / IP restrictions.

Going from OpenGL 2.1 to OpenGL 3.0 is a huge change, so hopefully once the OpenGL 3.0 support is in place, filling in the OpenGL 3.1, 3.2, and 3.3 revisions will take less time. There's also then OpenGL 4.0, 4.1, and 4.2 to now handle. There's a variety of comments within the Phoronix Forums about the OpenGL 4.2 revision, but I would still expect it to be at least two years before Mesa is caught up to the OpenGL 4.2 support level (with the necessary GLSL changes). That also doesn't account for the future OpenGL revisions to be released between now and then. It's a constant game of catch-up for the open-source drivers.

For those interested, below is the GL3/GL4 TODO list (from the Mesa Git tree) that details the current status of key features for each OpenGL 3.x/4.x revision. Even with the features marked as being done, the current code may be limited to supporting a particular graphics driver.

GL 3.0:

GLSL 1.30 (GL_EXT_gpu_shader4, etc.)                  started
Conditional rendering (GL_NV_conditional_render)      DONE (swrast, softpipe, i965)
Map buffer subranges (GL_ARB_map_buffer_range)        DONE
Clamping controls (GL_ARB_color_buffer_float)         DONE
Float textures, renderbuffers (GL_ARB_texture_float)  DONE (gallium r300)
GL_EXT_packed_float                                   DONE (gallium r600)
GL_EXT_texture_shared_exponent                        DONE (gallium, swrast)
Float depth buffers (GL_ARB_depth_buffer_float)       DONE
Framebuffer objects (GL_EXT_framebuffer_object)       DONE
Half-float                                            DONE
Multisample blit                                      DONE
Non-normalized Integer texture/framebuffer formats    ~50% done
1D/2D Texture arrays                                  core Mesa, swrast done
Packed depth/stencil formats                          DONE
Per-buffer blend and masks (GL_EXT_draw_buffers2)     DONE
GL_EXT_texture_compression_rgtc                       DONE (swrast, gallium r600)
Red and red/green texture formats                     DONE (swrast, i965, gallium)
Transform feedback (GL_EXT_transform_feedback)        ~50% done
   glBindFragDataLocation, glGetFragDataLocation,
   glBindBufferRange, glBindBufferBase commands
Vertex array objects (GL_APPLE_vertex_array_object)   DONE
sRGB framebuffer format (GL_EXT_framebuffer_sRGB)     core GL done (i965, gallium), GLX todo
glClearBuffer commands                                DONE
glGetStringi command                                  DONE
glTexParameterI, glGetTexParameterI commands          DONE
glVertexAttribI commands                              DONE (but converts int
                                                            values to floats)
Depth format cube textures                            0% done
GLX_ARB_create_context (GLX 1.4 is required)          not started


GL 3.1:

GLSL 1.40                                             not started
Instanced drawing (GL_ARB_draw_instanced)             DONE (gallium, swrast)
Buffer copying (GL_ARB_copy_buffer)                   DONE
Primitive restart (GL_NV_primitive_restart)           DONE (gallium)
16 vertex texture image units                         DONE
Texture buffer objs (GL_ARB_texture_buffer_object)    not started
Rectangular textures (GL_ARB_texture_rectangle)       DONE
Uniform buffer objs (GL_ARB_uniform_buffer_object)    not started
Signed normalized textures (GL_EXT_texture_snorm)     DONE (gallium)


GL 3.2:

Core/compatibility profiles                           not started
GLSL 1.50                                             not started
Geometry shaders (GL_ARB_geometry_shader4)            partially done (Zack)
BGRA vertex order (GL_ARB_vertex_array_bgra)          DONE
Base vertex offset(GL_ARB_draw_elements_base_vertex)  DONE
Frag shader coord (GL_ARB_fragment_coord_conventions) DONE (swrast, gallium)
Provoking vertex (GL_ARB_provoking_vertex)            DONE
Seamless cubemaps (GL_ARB_seamless_cube_map)          DONE
Multisample textures (GL_ARB_texture_multisample)     not started
Frag depth clamp (GL_ARB_depth_clamp)                 DONE
Fence objects (GL_ARB_sync)                           DONE
GLX_ARB_create_context_profile                        not started


GL 3.3:

GLSL 3.30                                             not started
GL_ARB_blend_func_extended                            not started
GL_ARB_explicit_attrib_location                       DONE (swrast, i915, i965)
GL_ARB_occlusion_query2                               DONE (swrast, gallium)
GL_ARB_sampler_objects                                DONE (gallium)
GL_ARB_texture_rgb10_a2ui                             not started
GL_ARB_texture_swizzle                                DONE (same as EXT version)
GL_ARB_timer_query                                    ~60% done (the EXT variant)
GL_ARB_instanced_arrays                               DONE (gallium)
GL_ARB_vertex_type_2_10_10_10_rev                     not started


GL 4.0:

GLSL 4.0                                             not started
GL_ARB_texture_query_lod                             not started
GL_ARB_draw_buffers_blend                            DONE (gallium softpipe)
GL_ARB_draw_indirect                                 not started
GL_ARB_gpu_shader_fp64                               not started
GL_ARB_sample_shading                                not started
GL_ARB_shader_subroutine                             not started
GL_ARB_tessellation_shader                           not started
GL_ARB_texture_buffer_object_rgb32                   not started
GL_ARB_texture_cube_map_array                        not started
GL_ARB_texture_gather                                not started
GL_ARB_transform_feedback2                           not started
GL_ARB_transform_feedback3                           not started


GL 4.1:

GLSL 4.1                                             not started
GL_ARB_ES2_compatibility                             DONE (i965)
GL_ARB_get_program_binary                            not started
GL_ARB_separate_shader_objects                       some infrastructure done
GL_ARB_shader_precision                              not started
GL_ARB_vertex_attrib_64bit                           not started
GL_ARB_viewport_array                                not started


GL 4.2:
GLSL 4.2                                             not started
GL_ARB_texture_compression_bptc                      not started
GL_ARB_compressed_texture_pixel_storage              not started
GL_ARB_shader_atomic_counters                        not started
GL_ARB_texture_storage                               not started
GL_ARB_transform_feedback_instanced                  not started
GL_ARB_base_instance                                 not started
GL_ARB_shader_image_load_store                       not started
GL_ARB_conservative_depth                            not started (may be close to AMD_conservative_depth though)
GL_ARB_shading_language_420pack                      not started
GL_ARB_internalformat_query                          not started
GL_ARB_map_buffer_alignment                          not started