src/gallium/docs/source/resources.rst

   1 Resources and derived objects
   2 =============================
   3
   4 Resources represent objects that hold data: textures and buffers.
   5
   6 They are mostly modelled after the resources in Direct3D 10/11, but with a
   7 different transfer/update mechanism, and more features for OpenGL support.
   8
   9 Resources can be used in several ways, and it is required to specify all planned uses through an appropriate set of bind flags.
  10
  11 TODO: write much more on resources
  12
  13 Transfers
  14 ---------
  15
  16 Transfers are the mechanism used to access resources with the CPU.
  17
  18 OpenGL: OpenGL supports mapping buffers and has inline transfer functions for both buffers and textures
  19
  20 D3D11: D3D11 lacks transfers, but has special resource types that are mappable to the CPU address space
  21
  22 TODO: write much more on transfers
  23
  24 Resource targets
  25 ----------------
  26
  27 Resource targets determine the type of a resource.
  28
  29 Note that drivers may not actually have the restrictions listed regarding
  30 coordinate normalization and wrap modes, and in fact efficient OpenCL
  31 support will probably require drivers that don't have any of them, which
  32 will probably be advertised with an appropriate cap.
  33
  34 TODO: document all targets. Note that both 3D and cube have restrictions
  35 that depend on the hardware generation.
  36
  37 TODO: can buffers have a non-R8 format?
  38
  39 PIPE_BUFFER
  40 ^^^^^^^^^^^
  41
  42 Buffer resource: can be used as a vertex, index, constant buffer (appropriate bind flags must be requested).
  43
  44 They can be bound to stream output if supported.
  45 TODO: what about the restrictions lifted by the several later GL transform feedback extensions? How does one advertise that in Gallium?
  46
  47 They can be also be bound to a shader stage as usual.
  48 TODO: are all drivers supposed to support this? how does this work exactly? are there size limits?
  49
  50 They can be also be bound to the framebuffer as usual.
  51 TODO: are all drivers supposed to support this? how does this work exactly? are there size limits?
  52 TODO: is there any chance of supporting GL pixel buffer object acceleration with this?
  53
  54 - depth0 must be 1
  55 - last_level must be 0
  56 - TODO: what about normalization?
  57 - TODO: wrap modes/other sampling state?
  58 - TODO: are arbitrary formats supported? in which cases?
  59
  60 OpenGL: vertex buffers in GL 1.5 or GL_ARB_vertex_buffer_object
  61
  62 - Binding to stream out requires GL 3.0 or GL_NV_transform_feedback
  63 - Binding as constant buffers requires GL 3.1 or GL_ARB_uniform_buffer_object
  64 - Binding to a sampling stage requires GL 3.1 or GL_ARB_texture_buffer_object
  65 - TODO: can they be bound to an FBO?
  66
  67 D3D11: buffer resources
  68 - Binding to a render target requires D3D_FEATURE_LEVEL_10_0
  69
  70 PIPE_TEXTURE_1D
  71 ^^^^^^^^^^^^^^^
  72 1D surface accessed with normalized coordinates.
  73
  74 UNIMPLEMENTED: 1D texture arrays not supported
  75
  76 - If PIPE_CAP_NPOT_TEXTURES is not supported,
  77       width must be a power of two
  78 - height0 must be 1
  79 - depth0 must be 1
  80 - Mipmaps can be used
  81 - Must use normalized coordinates
  82
  83 OpenGL: GL_TEXTURE_1D in GL 1.0
  84
  85 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
  86
  87 D3D11: 1D textures in D3D_FEATURE_LEVEL_10_0
  88
  89 PIPE_TEXTURE_RECT
  90 ^^^^^^^^^^^^^^^^^
  91 2D surface with OpenGL GL_TEXTURE_RECTANGLE semantics.
  92
  93 - depth0 must be 1
  94 - last_level must be 0
  95 - Must use unnormalized coordinates
  96 - Must use a clamp wrap mode
  97
  98 OpenGL: GL_TEXTURE_RECTANGLE in GL 3.1 or GL_ARB_texture_rectangle or GL_NV_texture_rectangle
  99
 100 OpenCL: can create OpenCL images based on this, that can then be sampled arbitrarily
 101
 102 D3D11: not supported (only PIPE_TEXTURE_2D with normalized coordinates is supported)
 103
 104 PIPE_TEXTURE_2D
 105 ^^^^^^^^^^^^^^^
 106 2D surface accessed with normalized coordinates.
 107
 108 UNIMPLEMENTED: 2D texture arrays not supported
 109
 110 - If PIPE_CAP_NPOT_TEXTURES is not supported,
 111       width and height must be powers of two
 112 - depth0 must be 1
 113 - Mipmaps can be used
 114 - Must use normalized coordinates
 115 - No special restrictions on wrap modes
 116
 117 OpenGL: GL_TEXTURE_2D in GL 1.0
 118
 119 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
 120
 121 OpenCL: can create OpenCL images based on this, that can then be sampled arbitrarily
 122
 123 D3D11: 2D textures
 124
 125 - PIPE_CAP_NPOT_TEXTURES is equivalent to D3D_FEATURE_LEVEL_9_3
 126
 127 PIPE_TEXTURE_3D
 128 ^^^^^^^^^^^^^^^
 129
 130 3-dimensional array of texels.
 131 Mipmap dimensions are reduced in all 3 coordinates.
 132
 133 - If PIPE_CAP_NPOT_TEXTURES is not supported,
 134       width, height and depth must be powers of two
 135 - Must use normalized coordinates
 136
 137 OpenGL: GL_TEXTURE_3D in GL 1.2 or GL_EXT_texture3D
 138
 139 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
 140
 141 D3D11: 3D textures
 142
 143 - PIPE_CAP_NPOT_TEXTURES is equivalent to D3D_FEATURE_LEVEL_10_0
 144
 145 PIPE_TEXTURE_CUBE
 146 ^^^^^^^^^^^^^^^^^
 147
 148 Cube maps consist of 6 2D faces.
 149 The 6 surfaces form an imaginary cube, and sampling happens by mapping an
 150 input 3-vector to the point of the cube surface in that direction.
 151
 152 Sampling may be optionally seamless, resulting in filtering taking samples
 153 from multiple surfaces near to the edge.
 154 UNIMPLEMENTED: seamless cube map sampling not supported
 155
 156 UNIMPLEMENTED: cube map arrays not supported
 157
 158 - Width and height must be equal
 159 - If PIPE_CAP_NPOT_TEXTURES is not supported,
 160       width and height must be powers of two
 161 - Must use normalized coordinates
 162
 163 OpenGL: GL_TEXTURE_CUBE_MAP in GL 1.3 or EXT_texture_cube_map
 164
 165 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
 166 - Seamless cube maps require GL 3.2 or GL_ARB_seamless_cube_map or GL_AMD_seamless_cubemap_per_texture
 167 - Cube map arrays require GL 4.0 or GL_ARB_texture_cube_map_array
 168
 169 D3D11: 2D array textures with the D3D11_RESOURCE_MISC_TEXTURECUBE flag
 170
 171 - PIPE_CAP_NPOT_TEXTURES is equivalent to D3D_FEATURE_LEVEL_10_0
 172 - Cube map arrays require D3D_FEATURE_LEVEL_10_1
 173 - TODO: are (non)seamless cube maps supported in D3D11? how?
 174
 175 Surfaces
 176 --------
 177
 178 Surfaces are views of a resource that can be bound as a framebuffer to serve as the render target or depth buffer.
 179
 180 TODO: write much more on surfaces
 181
 182 OpenGL: FBOs are collections of surfaces in GL 3.0 or GL_ARB_framebuffer_object
 183
 184 D3D11: render target views and depth/stencil views
 185
 186 Sampler views
 187 -------------
 188
 189 Sampler views are views of a resource that can be bound to a pipeline stage to be sampled from shaders.
 190
 191 TODO: write much more on sampler views
 192
 193 OpenGL: texture objects are actually sampler view and resource in a single unit
 194
 195 D3D11: shader resource views