A python wrapper around a subset of the ncollide rust library
A python library for spatial queries of points and line segments with meshes. ncollpyde wraps around a subset of the parry rust library (formerly its predecessor ncollide).
Free software: MIT License
pip install ncollpyde
Pre-built wheels are available for Linux, MacOS, and Windows. If you have a stable rust compiler, you should also be able to install from source.
Checking whether points are inside a volume defined by a triangular mesh
Checking the intersection of line segments with the mesh
Get the (signed) distance from points to the boundary of a mesh
This library implements most of its functionality through the Volume class, instantiated from an array of vertices, and an array of triangles as indices into the vertex array.
# get an array of vertices and triangles which refer to those points import meshio mesh = meshio.read("meshes/teapot.stl") # use this library from ncollpyde import Volume volume = Volume(mesh.points, mesh.cells_dict["triangle"]) # or, for convenience volume = Volume.from_meshio(mesh) # containment checks: singular and multiple assert [-2.30, -4.15, 1.90] in volume assert np.array_equal( volume.contains( [ [-2.30, -4.15, 1.90], [-0.35, -0.51, 7.61], ] ), [True, False] ) # line segment intersection seg_idxs, intersections, is_backface = volume.intersections( [[-10, -10, -10], [0, 0, 3], [10, 10, 10]], [[0, 0, 3], [10, 10, 10], [20, 20, 20]], ) assert np.array_equal(seg_idxs, [0, 1]) # idx 2 does not intersect assert np.array_equal(seg_idxs, [0, 1]) assert np.allclose( intersections, [ [-2.23347309, -2.23347309, 0.09648498], [ 3.36591285, 3.36591285, 5.356139], ], ) assert np.array_equal( is_backface, [False, True], ) # distance from boundary (negative means internal) assert np.array_equal( volume.distance([[10, 10, 10], [0, 0, 3]]), [10.08592464, -2.99951118], )
See the API docs for more advanced usage.
Performance gains for multi-threaded queries are underwhelming, especially for ray intersections: see this issue
- Very rare false positives for containment
Due to a bug in the underlying library
Only happens when the point is outside the mesh and fires a ray which touches a single edge or vertex of the mesh.
Also affects is_backface result for ray intersection checks
manylinux-compatible wheels are built on CI but not necessarily in your local environment. Always allow CI to deploy the wheels.
If you are installing from a source distribution rather than a wheel, you need a compatible rust toolchain
Meshes with >= ~4.3bn vertices are not supported, as the underlying library uses u32 to address them. This is probably not a problem at time of writing; such a mesh would take up hundreds of GB of RAM to operate on.
ncollpyde v0.11 was the last to support meshio < 4.0.
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