ncollpyde 0.16.0

A python wrapper around a subset of the ncollide rust library

A python wrapper around a subset of the ncollide rust library

• Free software: MIT License

• Documentation: https://ncollpyde.readthedocs.io.

Install

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.

Features

• Checking whether points are inside a volume defined by a triangular mesh

• Checking the intersection of line segments with the mesh

Usage

# get an array of vertices and triangles which refer to those points
import meshio
mesh = meshio.read("tests/teapot.stl")
vertices = mesh.points
triangles = mesh.cells_dict["triangle"]

# use this library
from ncollpyde import Volume

volume = Volume(vertices, triangles)

Containment checks:

# individual points (as 3-length array-likes) can be checked with `in`
assert [-2.3051376, -4.1556454,  1.9047838] in volume
assert [-0.35222054, -0.513299, 7.6191354] not in volume

# many points (as an Nx3 array-like) can be checked with the `contains` method
bools = volume.contains(np.array([
    [-2.3051376, -4.1556454,  1.9047838],
    [-0.35222054, -0.513299, 7.6191354],
]))
assert np.array_equal(bools, [True, False])

# checks can be parallelised
volume.contains(np.random.random((1000, 3)), threads=4)

Note that v0.11 was the last to support meshio < 4.0.

Known issues

• 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.