Proposal: read-write storage textures #3838

#1772 proposes adding read-write storage textures, and mentions that support will have to depend on the format.

This proposal suggests how read-write texture formats should be bucketed.

• rw-storage-texture-tier-1 extension covers:

  • r32float
  • r32uint
  • r32sint

  Metal: Needs MTLReadWriteTextureTier1
  D3D FL11: Available
  Vulkan: Available
  OpenGL ES 3.1: Available

• rw-storage-texture-tier-2 extension covers:

  • rgba32float
  • rgba32uint
  • rgba32sint
  • rgba16float
  • rgba16uint
  • rgba16sint
  • rgba8unorm
  • rgba8uint
  • rgba8sint

  Metal: Needs MTLReadWriteTextureTier2
  D3D FL11: Optional (see D3D Docs)
  Vulkan: Available
  OpenGL ES 3.1: Available

• rw-storage-texture-tier-3 extension covers:

  • r16float
  • r16uint
  • r16sint
  • r8unorm
  • r8uint
  • r8sint

  Metal: Needs MTLReadWriteTextureTier2
  D3D FL11: Optional (see D3D Docs)
  Vulkan: Needs shaderStorageImageExtendedFormats
  OpenGL ES 3.1: Unavailable

Note that rw-storage-texture-tier-3 might not be required if we require rw-storage-texture-tier-2 + formats-tier-1 for the respective formats.