forked from Qortal/Brooklyn
68 lines
2.8 KiB
ReStructuredText
68 lines
2.8 KiB
ReStructuredText
NIR Texture Instructions
|
|
========================
|
|
|
|
Even though texture instructions *could* be supported as intrinsics, the vast
|
|
number of combinations mean that doing so is practically impossible. Instead,
|
|
NIR has a dedicated texture instruction. There are several texture operations:
|
|
|
|
.. doxygenenum:: nir_texop
|
|
|
|
As with other instruction types, there is still an array of sources, except
|
|
that each source also has a *type* associated with it. There are various
|
|
source types, each corresponding to a piece of information that the different
|
|
texture operations require.
|
|
|
|
.. doxygenenum:: nir_tex_src_type
|
|
|
|
Of particular interest are the texture/sampler deref/index/handle source types.
|
|
First, note that textures and samplers are specified separately in NIR. While
|
|
not required for OpenGL, this is required for Vulkan and OpenCL. Some
|
|
OpenGL [ES] drivers have to deal with hardware that does not have separate
|
|
samplers and textures. While not recommended, an OpenGL-only driver may assume
|
|
that the texture and sampler derefs will always point to the same resource, if
|
|
needed. Note that this pretty well paints your compiler into a corner and
|
|
makes any future port to Vulkan or OpenCL harder, so such assumptions should
|
|
really only be made if targeting OpenGL ES 2.0 era hardware.
|
|
|
|
Also, like a lot of other resources, there are multiple ways to represent a
|
|
texture in NIR. It can be referenced by a variable dereference, an index, or a
|
|
bindless handle. When using an index or a bindless handle, the texture type
|
|
information is generally not available. To handle this, various information
|
|
from the type is redundantly stored in the :cpp:struct:`nir_tex_instr` itself.
|
|
|
|
.. doxygenstruct:: nir_tex_instr
|
|
:members:
|
|
|
|
.. doxygenstruct:: nir_tex_src
|
|
:members:
|
|
|
|
Texture instruction helpers
|
|
---------------------------
|
|
|
|
There are a number of helper functions for working with NIR texture
|
|
instructions. They are documented here in no particular order.
|
|
|
|
.. doxygenfunction:: nir_tex_instr_create
|
|
.. doxygenfunction:: nir_tex_instr_need_sampler
|
|
.. doxygenfunction:: nir_tex_instr_result_size
|
|
.. doxygenfunction:: nir_tex_instr_dest_size
|
|
.. doxygenfunction:: nir_tex_instr_is_query
|
|
.. doxygenfunction:: nir_tex_instr_has_implicit_derivative
|
|
.. doxygenfunction:: nir_tex_instr_src_type
|
|
.. doxygenfunction:: nir_tex_instr_src_size
|
|
.. doxygenfunction:: nir_tex_instr_src_index
|
|
.. doxygenfunction:: nir_tex_instr_add_src
|
|
.. doxygenfunction:: nir_tex_instr_remove_src
|
|
|
|
Texture instruction lowering
|
|
----------------------------
|
|
|
|
Because most hardware only supports some subset of all possible GLSL/SPIR-V
|
|
texture operations, NIR provides a quite powerful lowering pass which is able
|
|
to implement more complex texture operations in terms of simpler ones.
|
|
|
|
.. doxygenfunction:: nir_lower_tex
|
|
.. doxygenstruct:: nir_lower_tex_options
|
|
:members:
|
|
.. doxygenenum:: nir_lower_tex_packing
|