3 Resources and derived objects
4 =============================
6 Resources represent objects that hold data: textures and buffers.
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.
11 Resources can be used in several ways, and it is required to specify all planned uses through an appropriate set of bind flags.
13 TODO: write much more on resources
18 Transfers are the mechanism used to access resources with the CPU.
20 OpenGL: OpenGL supports mapping buffers and has inline transfer functions for both buffers and textures
22 D3D11: D3D11 lacks transfers, but has special resource types that are mappable to the CPU address space
24 TODO: write much more on transfers
29 Resource targets determine the type of a resource.
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.
36 TODO: document all targets. Note that both 3D and cube have restrictions
37 that depend on the hardware generation.
43 Buffer resource: can be used as a vertex, index, constant buffer
44 (appropriate bind flags must be requested).
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).
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?
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).
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?
72 OpenGL: vertex buffers in GL 1.5 or GL_ARB_vertex_buffer_object
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
78 D3D11: buffer resources
79 - Binding to a render target requires D3D_FEATURE_LEVEL_10_0
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.
86 - If PIPE_CAP_NPOT_TEXTURES is not supported,
87 width must be a power of two
90 - array_size must be 1 for PIPE_TEXTURE_1D
92 - Must use normalized coordinates
94 OpenGL: GL_TEXTURE_1D in GL 1.0
96 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
98 D3D11: 1D textures in D3D_FEATURE_LEVEL_10_0
102 2D surface with OpenGL GL_TEXTURE_RECTANGLE semantics.
105 - array_size must be 1
106 - last_level must be 0
107 - Must use unnormalized coordinates
108 - Must use a clamp wrap mode
110 OpenGL: GL_TEXTURE_RECTANGLE in GL 3.1 or GL_ARB_texture_rectangle or GL_NV_texture_rectangle
112 OpenCL: can create OpenCL images based on this, that can then be sampled arbitrarily
114 D3D11: not supported (only PIPE_TEXTURE_2D with normalized coordinates is supported)
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.
121 - If PIPE_CAP_NPOT_TEXTURES is not supported,
122 width and height must be powers of two
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
129 OpenGL: GL_TEXTURE_2D in GL 1.0
131 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
133 OpenCL: can create OpenCL images based on this, that can then be sampled arbitrarily
137 - PIPE_CAP_NPOT_TEXTURES is equivalent to D3D_FEATURE_LEVEL_9_3
142 3-dimensional array of texels.
143 Mipmap dimensions are reduced in all 3 coordinates.
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
150 OpenGL: GL_TEXTURE_3D in GL 1.2 or GL_EXT_texture3D
152 - PIPE_CAP_NPOT_TEXTURES is equivalent to GL 2.0 or GL_ARB_texture_non_power_of_two
156 - PIPE_CAP_NPOT_TEXTURES is equivalent to D3D_FEATURE_LEVEL_10_0
158 PIPE_TEXTURE_CUBE / PIPE_TEXTURE_CUBE_ARRAY
159 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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.
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.
169 - Width and height must be equal
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
176 OpenGL: GL_TEXTURE_CUBE_MAP in GL 1.3 or EXT_texture_cube_map
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
182 D3D11: 2D array textures with the D3D11_RESOURCE_MISC_TEXTURECUBE flag
184 - PIPE_CAP_NPOT_TEXTURES is equivalent to D3D_FEATURE_LEVEL_10_0
185 - Cube map arrays require D3D_FEATURE_LEVEL_10_1
190 Surfaces are views of a resource that can be bound as a framebuffer to serve as the render target or depth buffer.
192 TODO: write much more on surfaces
194 OpenGL: FBOs are collections of surfaces in GL 3.0 or GL_ARB_framebuffer_object
196 D3D11: render target views and depth/stencil views
201 Sampler views are views of a resource that can be bound to a pipeline stage to be sampled from shaders.
203 TODO: write much more on sampler views
205 OpenGL: texture objects are actually sampler view and resource in a single unit
207 D3D11: shader resource views