docs/gallium/resources.rst

   1 .. _resource:
   2
   3 Resources and derived objects
   4 =============================
   5
   6 Resources represent objects that hold data: textures and buffers.
   7
   8 They are mostly modelled after the resources in Direct3D 10/11, but with a
   9 different transfer/update mechanism, and more features for OpenGL support.
  10
  11 Resources can be used in several ways, and it is required to specify all planned uses through an appropriate set of bind flags.
  12
  13 TODO: write much more on resources
  14
  15 Transfers
  16 ---------
  17
  18 Transfers are the mechanism used to access resources with the CPU.
  19
  20 OpenGL: OpenGL supports mapping buffers and has inline transfer functions for both buffers and textures
  21
  22 D3D11: D3D11 lacks transfers, but has special resource types that are mappable to the CPU address space
  23
  24 TODO: write much more on transfers
  25
  26 Resource targets
  27 ----------------
  28
  29 Resource targets determine the type of a resource.
  30
  31 Note that drivers may not actually have the restrictions listed regarding
  32 coordinate normalization and wrap modes, and in fact efficient OpenCL
  33 support will probably require drivers that don't have any of them, which
  34 will probably be advertised with an appropriate cap.
  35
  36 TODO: document all targets. Note that both 3D and cube have restrictions
  37 that depend on the hardware generation.
  38
  39
  40 PIPE_BUFFER
  41 ^^^^^^^^^^^
  42
  43 Buffer resource: can be used as a vertex, index, constant buffer
  44 (appropriate bind flags must be requested).
  45
  46 Buffers do not really have a format, it's just bytes, but they are required
  47 to have their type set to a R8 format (without a specific "just byte" format,
  48 R8_UINT would probably make the most sense, but for historic reasons R8_UNORM
  49 is ok too). (This is just to make some shared buffer/texture code easier so
  50 format size can be queried.)
  51 width0 serves as size, most other resource properties don't apply but must be
  52 set appropriately (depth0/height0/array_size must be 1, last_level 0).
  53
  54 They can be bound to stream output if supported.
  55 TODO: what about the restrictions lifted by the several later GL transform feedback extensions? How does one advertise that in Gallium?
  56
  57 They can be also be bound to a shader stage (for sampling) as usual by
  58 creating an appropriate sampler view, if the driver supports PIPE_CAP_TEXTURE_BUFFER_OBJECTS.
  59 This supports larger width than a 1d texture would
  60 (TODO limit currently unspecified, minimum must be at least 65536).
  61 Only the "direct fetch" sample opcodes are supported (TGSI_OPCODE_TXF,
  62 TGSI_OPCODE_SAMPLE_I) so the sampler state (coord wrapping etc.)
  63 is mostly ignored (with SAMPLE_I there's no sampler state at all).
  64
  65 They can be also be bound to the framebuffer (only as color render target, not
  66 depth buffer, also there cannot be a depth buffer bound at the same time) as usual
  67 by creating an appropriate view (this is not usable in OpenGL).
  68 TODO there's no CAP bit currently for this, there's also unspecified size etc. limits
  69 TODO: is there any chance of supporting GL pixel buffer object acceleration with this?
  70
  71
  72 OpenGL: vertex buffers in GL 1.5 or GL_ARB_vertex_buffer_object
  73
  74 - Binding to stream out requires GL 3.0 or GL_NV_transform_feedback
  75 - Binding as constant buffers requires GL 3.1 or GL_ARB_uniform_buffer_object
  76 - Binding to a sampling stage requires GL 3.1 or GL_ARB_texture_buffer_object
  77
  78 D3D11: buffer resources
  79 - Binding to a render target requires D3D_FEATURE_LEVEL_10_0
  80
  81 PIPE_TEXTURE_1D / PIPE_TEXTURE_1D_ARRAY
  82 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  83 1D surface accessed with normalized coordinates.
  84 1D array textures are supported depending on PIPE_CAP_MAX_TEXTURE_ARRAY_LAYERS.
  85
  86 - If PIPE_CAP_NPOT_TEXTURES is not supported,
  87       width must be a power of two
  88 - height0 must be 1
  89 - depth0 must be 1
  90 - array_size must be 1 for PIPE_TEXTURE_1D
  91 - Mipmaps can be used
  92 - Must use normalized coordinates
  93
  94 OpenGL: GL_TEXTURE_1D in GL 1.0
  95
  96 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
  97
  98 D3D11: 1D textures in D3D_FEATURE_LEVEL_10_0
  99
 100 PIPE_TEXTURE_RECT
 101 ^^^^^^^^^^^^^^^^^
 102 2D surface with OpenGL GL_TEXTURE_RECTANGLE semantics.
 103
 104 - depth0 must be 1
 105 - array_size must be 1
 106 - last_level must be 0
 107 - Must use unnormalized coordinates
 108 - Must use a clamp wrap mode
 109
 110 OpenGL: GL_TEXTURE_RECTANGLE in GL 3.1 or GL_ARB_texture_rectangle or GL_NV_texture_rectangle
 111
 112 OpenCL: can create OpenCL images based on this, that can then be sampled arbitrarily
 113
 114 D3D11: not supported (only PIPE_TEXTURE_2D with normalized coordinates is supported)
 115
 116 PIPE_TEXTURE_2D / PIPE_TEXTURE_2D_ARRAY
 117 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 118 2D surface accessed with normalized coordinates.
 119 2D array textures are supported depending on PIPE_CAP_MAX_TEXTURE_ARRAY_LAYERS.
 120
 121 - If PIPE_CAP_NPOT_TEXTURES is not supported,
 122       width and height must be powers of two
 123 - depth0 must be 1
 124 - array_size must be 1 for PIPE_TEXTURE_2D
 125 - Mipmaps can be used
 126 - Must use normalized coordinates
 127 - No special restrictions on wrap modes
 128
 129 OpenGL: GL_TEXTURE_2D in GL 1.0
 130
 131 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
 132
 133 OpenCL: can create OpenCL images based on this, that can then be sampled arbitrarily
 134
 135 D3D11: 2D textures
 136
 137 - PIPE_CAP_NPOT_TEXTURES is equivalent to D3D_FEATURE_LEVEL_9_3
 138
 139 PIPE_TEXTURE_3D
 140 ^^^^^^^^^^^^^^^
 141
 142 3-dimensional array of texels.
 143 Mipmap dimensions are reduced in all 3 coordinates.
 144
 145 - If PIPE_CAP_NPOT_TEXTURES is not supported,
 146       width, height and depth must be powers of two
 147 - array_size must be 1
 148 - Must use normalized coordinates
 149
 150 OpenGL: GL_TEXTURE_3D in GL 1.2 or GL_EXT_texture3D
 151
 152 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
 153
 154 D3D11: 3D textures
 155
 156 - PIPE_CAP_NPOT_TEXTURES is equivalent to D3D_FEATURE_LEVEL_10_0
 157
 158 PIPE_TEXTURE_CUBE / PIPE_TEXTURE_CUBE_ARRAY
 159 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 160
 161 Cube maps consist of 6 2D faces.
 162 The 6 surfaces form an imaginary cube, and sampling happens by mapping an
 163 input 3-vector to the point of the cube surface in that direction.
 164 Cube map arrays are supported depending on PIPE_CAP_CUBE_MAP_ARRAY.
 165
 166 Sampling may be optionally seamless if a driver supports it (PIPE_CAP_SEAMLESS_CUBE_MAP),
 167 resulting in filtering taking samples from multiple surfaces near to the edge.
 168
 169 - Width and height must be equal
 170 - depth0 must be 1
 171 - array_size must be a multiple of 6
 172 - If PIPE_CAP_NPOT_TEXTURES is not supported,
 173       width and height must be powers of two
 174 - Must use normalized coordinates
 175
 176 OpenGL: GL_TEXTURE_CUBE_MAP in GL 1.3 or EXT_texture_cube_map
 177
 178 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
 179 - Seamless cube maps require GL 3.2 or GL_ARB_seamless_cube_map or GL_AMD_seamless_cubemap_per_texture
 180 - Cube map arrays require GL 4.0 or GL_ARB_texture_cube_map_array
 181
 182 D3D11: 2D array textures with the D3D11_RESOURCE_MISC_TEXTURECUBE flag
 183
 184 - PIPE_CAP_NPOT_TEXTURES is equivalent to D3D_FEATURE_LEVEL_10_0
 185 - Cube map arrays require D3D_FEATURE_LEVEL_10_1
 186
 187 Surfaces
 188 --------
 189
 190 Surfaces are views of a resource that can be bound as a framebuffer to serve as the render target or depth buffer.
 191
 192 TODO: write much more on surfaces
 193
 194 OpenGL: FBOs are collections of surfaces in GL 3.0 or GL_ARB_framebuffer_object
 195
 196 D3D11: render target views and depth/stencil views
 197
 198 Sampler views
 199 -------------
 200
 201 Sampler views are views of a resource that can be bound to a pipeline stage to be sampled from shaders.
 202
 203 TODO: write much more on sampler views
 204
 205 OpenGL: texture objects are actually sampler view and resource in a single unit
 206
 207 D3D11: shader resource views