mtlbvh

Metal-accelerated BVH for distance queries and ray tracing on Apple Silicon.

Features

• Unsigned distance: closest point on mesh surface
• Signed distance: watertight (normal averaging) and raystab (ray stabbing) modes
• Ray tracing: ray-triangle intersection with BVH acceleration
• Barycentric coordinates: optional UVW output for all distance queries
• Zero-copy: tensors bind directly to Metal via Apple Silicon unified memory

4-wide BVH with stack-based traversal, sorting networks, and stackless fallback.

API-compatible with cubvh for drop-in use in existing pipelines.

Installation

Requires macOS 14+ on Apple Silicon, Xcode command line tools, and PyTorch >= 2.0.

pip install --no-build-isolation -e .
python setup.py build_ext --inplace

Usage

from mtlbvh import MtlBVH

bvh = MtlBVH(vertices, triangles)  # numpy or torch, [N,3] and [M,3]

# distance queries
distances, face_id, uvw = bvh.unsigned_distance(positions, return_uvw=True)
distances, face_id, uvw = bvh.signed_distance(positions, mode='watertight')

# ray tracing
hit_pos, face_id, depth = bvh.ray_trace(rays_o, rays_d)

License

MIT License

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Apple-Silicon follow-ups

Cross-repo follow-up work (deferred mtlgemm perf items, fp16/bf16 shader specializations, universal tiled sparse attention, etc.) is tracked in this repo's GitHub issues. Bug reports and PRs are welcome on any of the four mtl* repos — mtlbvh, mtlgemm, mtlmesh and mtldiffrast — and on trellis2-apple, which depends on all of them.