SSAO got merged in #7402, but there's still a lot we can do better.

Performance

• Faster depth->world position (see reverted code)
• Render at half resolution and use a bilateral upsample
• F16 math (missing naga-wgsl support [meta] f16 support gfx-rs/wgpu#4384)
• Faster depth mipchain creation (https://github.com/GPUOpen-Effects/FidelityFX-SPD) (wgpu/naga does not currently support subgroup ops)

Quality

• Replace the spatial denoiser with a combined spatial+temporal denoiser, similar to bevy_solari's
• Try interleaved gradient noise or tellusim's spatiotemporal blue noise for sampling
• Bent normals
• Better multibounce approximation (https://drive.google.com/file/d/1SyagcEVplIm2KkRD3WQYSO9O0Iyi1hfy/view)
• Configurable parameters/heuristics

Platform Support

• SSAO currently does not work on DirectX12 due to issues with wgpu and naga:
  • DX12 increase max_storage_buffers_per_shader_stage and max_storage_textures_per_shader_stage gfx-rs/wgpu#3798
  • Implement Pack/Unpack for HLSL gfx-rs/naga#2353 (we have a work-around for this issue in the SSAO shaders atm)
• SSAO currently does not work on WebGPU because r16float is not a valid storage texture format https://gpuweb.github.io/gpuweb/wgsl/#storage-texel-formats. We can fix this with a fallback to r32float.

Recent Algorithm Advancements

• Visibility bitmask (https://cdrinmatane.github.io/posts/ssaovb-code/, https://link.springer.com/article/10.1007/s00371-022-02703-y, https://cdrinmatane.github.io/posts/cgspotlight-slides/)
• Screen space diffuse lighting (https://github.com/Patapom/GodComplex/blob/master/Tests/TestHBIL/2018%20Mayaux%20-%20Horizon-Based%20Indirect%20Lighting%20(HBIL).pdf)