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D3D12 Opacity Micromaps

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Amar, Adam

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Description

A Microsoft DirectX Developer Blog post by Amar and Adam on Direct3D 12 Opacity Micromaps (OMMs) in DXR Tier 1.2 for cheaper alpha-tested geometry in ray tracing.

It covers coherent opacity versus costly AnyHit calls, micro-triangle barycentric subdivision, 1-bit and 2-bit encodings with opaque, transparent, and unknown states, 2-state versus 4-state modes, OMM Arrays built like acceleration structures, BLAS linkage via D3D12_RAYTRACING_GEOMETRY_OMM_TRIANGLES_DESC, and RayQuery needs under Shader Model 6.9. NVIDIA bakers, Agility SDK availability, and samples are noted.

Readers should be advanced DXR developers comfortable with BLAS builds. NVIDIA raytracing GPUs support OMMs first; other vendors are expected later.

The free blog has diagrams, feature-check snippets, DXR spec links, and sample pointers alongside SM 6.9 driver matrices.

It helps integrate alpha-tested content into DXR without paying full AnyHit cost on trivially opaque or transparent hits.