1NIR Texture Instructions 2======================== 3 4Even though texture instructions *could* be supported as intrinsics, the vast 5number of combinations mean that doing so is practically impossible. Instead, 6NIR has a dedicated texture instruction. There are several texture operations: 7 8.. doxygenenum:: nir_texop 9 10As with other instruction types, there is still an array of sources, except 11that each source also has a *type* associated with it. There are various 12source types, each corresponding to a piece of information that the different 13texture operations require. 14 15.. doxygenenum:: nir_tex_src_type 16 17Of particular interest are the texture/sampler deref/index/handle source types. 18First, note that textures and samplers are specified separately in NIR. While 19not required for OpenGL, this is required for Vulkan and OpenCL. Some 20OpenGL [ES] drivers have to deal with hardware that does not have separate 21samplers and textures. While not recommended, an OpenGL-only driver may assume 22that the texture and sampler derefs will always point to the same resource, if 23needed. Note that this pretty well paints your compiler into a corner and 24makes any future port to Vulkan or OpenCL harder, so such assumptions should 25really only be made if targeting OpenGL ES 2.0 era hardware. 26 27Also, like a lot of other resources, there are multiple ways to represent a 28texture in NIR. It can be referenced by a variable dereference, an index, or a 29bindless handle. When using an index or a bindless handle, the texture type 30information is generally not available. To handle this, various information 31from the type is redundantly stored in the :cpp:struct:`nir_tex_instr` itself. 32 33.. doxygenstruct:: nir_tex_instr 34 :members: 35 36.. doxygenstruct:: nir_tex_src 37 :members: 38 39Texture instruction helpers 40--------------------------- 41 42There are a number of helper functions for working with NIR texture 43instructions. They are documented here in no particular order. 44 45.. doxygenfunction:: nir_tex_instr_create 46.. doxygenfunction:: nir_tex_instr_need_sampler 47.. doxygenfunction:: nir_tex_instr_result_size 48.. doxygenfunction:: nir_tex_instr_dest_size 49.. doxygenfunction:: nir_tex_instr_is_query 50.. doxygenfunction:: nir_tex_instr_has_implicit_derivative 51.. doxygenfunction:: nir_tex_instr_src_type 52.. doxygenfunction:: nir_tex_instr_src_size 53.. doxygenfunction:: nir_tex_instr_src_index 54.. doxygenfunction:: nir_tex_instr_add_src 55.. doxygenfunction:: nir_tex_instr_remove_src 56 57Texture instruction lowering 58---------------------------- 59 60Because most hardware only supports some subset of all possible GLSL/SPIR-V 61texture operations, NIR provides a quite powerful lowering pass which is able 62to implement more complex texture operations in terms of simpler ones. 63 64.. doxygenfunction:: nir_lower_tex 65.. doxygenstruct:: nir_lower_tex_options 66 :members: 67.. doxygenenum:: nir_lower_tex_packing 68