Opacity Micromaps Support

[natevm]

Recent NVIDIA cards now support opacity micromaps.

Every subtriangle takes about 1 byte.

Opacity maps allow for masking subtriangles as transparent or opaque. This allows rays to pass through these subtriangles without calling into an anyhit program.

Then, micromeshes allow for fine level displacement on a single triangle, which is useful for techniques like displacement mapping.

For more details, this is a good reference.
https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_EXT_opacity_micromap.html

[natevm]

Using micromaps requires support for the VK_EXT_opacity_micromap device extension. This is available on all NVIDIA architectures supporting RT cores, including Turing.

https://vulkan.gpuinfo.org/listdevicescoverage.php?extension=VK_EXT_opacity_micromap&platform=all

[natevm]

Since last this was opened, the DMM extension has been discontinued. OMM was ratified in the DXR spec, and at least NV and Qualcomm supports it. So it’s worth considering