Summary:
Fixes https://github.com/facebookresearch/pytorch3d/issues/1934. Two independent bugs in the CPU backend.
### 1. Degenerate-triangle filter discards valid faces
`marching_cubes_cpu.cpp`, `marching_cubes.py`
`tri.clear()` and `ps.clear()` sit inside the degeneracy check, so the buffers only reset when a triangle is *accepted*. Once a cube's first triangle is degenerate, `ps[0..2]` stay frozen on it, and every subsequent triangle in that cube fails the same stale check and is dropped.
Fixed by gating on `ps.size() == 3` and clearing unconditionally. The old code could only ever drop faces, never emit incorrect ones, so this is strictly additive.
### 2. Edge hash computed in float32
`marching_cubes_utils.h`
`p[v].x/y/z` hold integral coordinates but are stored as `float`, so `x + y*W + z*W*H` evaluates entirely in float32 before truncating to `int`. float32 is exact only to 2²⁴ − 1 = 16,777,215 — and 256³ maxes out at exactly that value. At 512³ the maximum id is 134,217,727, where float32 spacing is 8, so distinct vertices collide on one id and `uniq_edge_id` merges them.
Fixed by widening `W/H/D` to `int64_t` and casting each coordinate before multiplying. Also tightens the stride from `(W + W*H + W*H*D)` to `W*H*D`. Raises the CPU ceiling from 256³ to 1448³.
Scope is the CPU path only. `marching_cubes_naive` was never affected (Python ints are arbitrary-precision), and neither was CUDA: `hashVpair` there computes ids in `uint` rather than `float`, so it has no 2²⁴ cliff, and `MarchingCubes` already rejects volumes above 1024³ before the CUDA kernel runs. The new `TORCH_CHECK` bound and the "~1448³" note in the new comments describe `MarchingCubesCpu` only.
### Verification
Ellipsoid SDF (0.1, 1, 1), `isolevel=0.0`, identical input tensors on both devices.
| Resolution | CUDA V | CUDA F | CPU V | CPU F | Degenerate dropped |
| -- | -- | -- | -- | -- | -- |
| 32³ | 1,664 | 3,324 | 1,664 | 3,324 | 0 |
| 64³ | 7,312 | 14,620 | 7,312 | 14,620 | 0 |
| 128³ | 30,168 | 60,332 | 30,168 | 60,332 | 0 |
| 256³ | 122,448 | 244,892 | 122,448 | 243,996 | 896 |
| 512³ | 491,944 | 983,884 | 491,944 | 976,140 | 7,744 |
Machine: Arch Linux, RTX 4080, Ryzen 7 7800X3D
Vertex counts now match CUDA exactly at every resolution; 512³ previously produced 176,121. The remaining face gap is entirely degenerate geometry — the CUDA mesh at 512³ contains exactly 7,744 zero-area triangles.
### Tests
`test_degenerate_triangle_keeps_later_faces` — a 2×2×2 volume at `isolevel=1` chosen so the cube's four candidate triangles collapse onto its four outside corners: triangles 1 and 4 become degenerate, 2 and 3 stay valid. Pre-fix, the first degeneracy suppresses the rest and the mesh comes back empty; post-fix it is the expected quad. Asserts both `marching_cubes_naive` and the C++ extension.
`test_large_grid_edge_ids` — a 2×2×4,200,000 volume (~67MB, ~0.1s) holding 16 isolated interior points on the highest-id grid row, positioned so grid-point ids straddle 2²⁴. Each point cuts exactly four grid edges, so the 64-vertex expectation is derived geometrically rather than copied from output. Pre-fix, a hash collision merges two edges and one vertex is lost.
All 26 pre-existing tests in `test_marching_cubes.py` pass **unchanged**. That includes `test_cube_no_duplicate_verts` (`isolevel=1`) and `test_sphere` (`isolevel=64`), which both exercise the degenerate path but whose output is identical before and after the fix — so no existing expectation was edited and `sphere_level64.pickle` does not need regenerating.
The imported diff contained no test file. The two tests above were written during import and differ from the tests described in the upstream PR description.
*Analysis and write-up done collaboratively with AI, figures from testing are done on my own machine and have been checked.*
Pull Request resolved: https://github.com/facebookresearch/pytorch3d/pull/2043
Test Plan:
```
buck2 test fbcode//vision/fair/pytorch3d:tests -- --regex 'test_marching_cubes'
```
`Pass 28. Fail 0.` — 26 pre-existing tests plus the 2 new regression tests.
Reverting all three source hunks to their pre-fix state and re-running the same command: both new tests fail (`test_degenerate_triangle_keeps_later_faces` returns an empty mesh instead of 4 verts / 2 faces; `test_large_grid_edge_ids` returns 31 verts instead of 32) and all 26 pre-existing tests still pass. The new tests are therefore pinned to exactly this change, and the change breaks nothing that was already covered.
Reviewed By: MichaelRamamonjisoa
Differential Revision: D115424433
Pulled By: bottler
fbshipit-source-id: 547a260010b94253f52f3a3c223d4c4fa78a7ee6
Summary:
Converts the directory specified to use the Ruff formatter in pyfmt
ruff_dog
If this diff causes merge conflicts when rebasing, please run
`hg status -n -0 --change . -I '**/*.{py,pyi}' | xargs -0 arc pyfmt`
on your diff, and amend any changes before rebasing onto latest.
That should help reduce or eliminate any merge conflicts.
allow-large-files
Reviewed By: bottler
Differential Revision: D66472063
fbshipit-source-id: 35841cb397e4f8e066e2159550d2f56b403b1bef
Summary:
Fixes https://github.com/facebookresearch/pytorch3d/issues/1641. The bug was caused by the mistaken downcasting of an int64_t into int, causing issues only on inputs large enough to have hashes that escaped the bounds of an int32.
Also added a test case for this issue.
Reviewed By: bottler
Differential Revision: D53505370
fbshipit-source-id: 0fdd0efc6d259cc3b0263e7ff3a4ab2c648ec521
Summary:
Torch C++ extension for Marching Cubes
- Add torch C++ extension for marching cubes. Observe a speed up of ~255x-324x speed up (over varying batch sizes and spatial resolutions)
- Add C++ impl in existing unit-tests.
(Note: this ignores all push blocking failures!)
Reviewed By: kjchalup
Differential Revision: D39590638
fbshipit-source-id: e44d2852a24c2c398e5ea9db20f0dfaa1817e457
Summary: Overhaul of marching_cubes_naive for better performance and to avoid relying on unstable hashing. In particular, instead of hashing vertex positions, we index each interpolated vertex with its corresponding edge in the 3d grid.
Reviewed By: kjchalup
Differential Revision: D39419642
fbshipit-source-id: b5fede3525c545d1d374198928dfb216262f0ec0
Summary:
Applies new import merging and sorting from µsort v1.0.
When merging imports, µsort will make a best-effort to move associated
comments to match merged elements, but there are known limitations due to
the diynamic nature of Python and developer tooling. These changes should
not produce any dangerous runtime changes, but may require touch-ups to
satisfy linters and other tooling.
Note that µsort uses case-insensitive, lexicographical sorting, which
results in a different ordering compared to isort. This provides a more
consistent sorting order, matching the case-insensitive order used when
sorting import statements by module name, and ensures that "frog", "FROG",
and "Frog" always sort next to each other.
For details on µsort's sorting and merging semantics, see the user guide:
https://usort.readthedocs.io/en/stable/guide.html#sorting
Reviewed By: bottler
Differential Revision: D35553814
fbshipit-source-id: be49bdb6a4c25264ff8d4db3a601f18736d17be1
Summary: Update all FB license strings to the new format.
Reviewed By: patricklabatut
Differential Revision: D33403538
fbshipit-source-id: 97a4596c5c888f3c54f44456dc07e718a387a02c
Summary: Simplify finding the data directories in the tests.
Reviewed By: nikhilaravi
Differential Revision: D27634293
fbshipit-source-id: dc308a7c86c41e6fae56a2ab58187c9f0335b575
Summary: Make common functions for finding directories where test data is found, instead of lots of tests using their own `__file__` while trying to get ./tests/data and the tutorials data.
Reviewed By: nikhilaravi
Differential Revision: D27633701
fbshipit-source-id: 1467bb6018cea16eba3cab097d713116d51071e9
Summary:
Defines a function to run marching cubes algorithm on a single or batch of 3D scalar fields. Returns a mesh's faces and vertices.
UPDATES (12/18)
- Input data is now specified as a (B, D, H, W) tensor as opposed to a (B, W, H, D) tensor. This will now be compatible with the Volumes datastructure.
- Add an option to return output vertices in local coordinates instead of world coordinates.
Also added a small fix to remove the dype for device in Transforms3D - if passing in a torch.device instead of str it causes a pyre error.
Reviewed By: jcjohnson
Differential Revision: D24599019
fbshipit-source-id: 90554a200319fed8736a12371cc349e7108aacd0
