Inaccuracies in mesh.contains

I experiencing some issues with the Trimesh.contains method. I tried to debug it myself, but I couldn’t find any issues in the trimesh code. I suspect it’s inaccuracies in PyEmbree.

Here is the code I’m using:

import numpy as np
import trimesh
from plyfile import PlyElement, PlyData

# Only for exporting the pointcloud
def export_pointcloud(vertices, out_file):
    assert(vertices.shape[1] == 3)
    vertices = vertices.astype(np.float32)
    vector_dtype = [('x', 'f4'), ('y', 'f4'), ('z', 'f4')]
    vertices = vertices.view(dtype=vector_dtype).flatten()
    plyel = PlyElement.describe(vertices, 'vertex')
    plydata = PlyData([plyel], text=True)
    plydata.write(out_file)

# Load mesh
mesh = trimesh.load('voxels.off', process=False)
points = np.random.rand(100000, 3) - 0.5
contained = mesh.contains(points)
export_pointcloud(points[contained], 'points.ply')

The result looks like this:

Here are the input / output files: https://www.dropbox.com/sh/6i0222tk9lpkqgr/AAC1mZ0yblFsXxg9cEMmfneJa?dl=0

Of course, in this special case I can do it in a simpler way by exploiting the regular grid structure of the mesh. However, I also experience similar problems for other meshes (usually at higher resolutions).

I would appreciate any help!

[LMescheder]

I ended up writing my own cython code for checking if a point is inside a mesh, based on this answer stack overflow: https://stackoverflow.com/a/6576840 As far as I can tell, it works quite robustly and yields more accurate results. I would be happy to contribute the code (not now, but in a few weeks) if you are interested.

[benoitrosa]

Hi,

For easy testing, you can download the inside_mesh.py and triangle_hash.pyx files from the Occupancy Network repo, and compile the pyx file. You just have to create a setup.py file with the following lines :

`from distutils.core import setup from Cython.Build import cythonize

setup( ext_modules = cythonize(“triangle_hash.pyx”) )`

And then compile it using cython : python setup.py build_ext --inplace

The compilation creates a triangle_hash.so which can be imported in python normally, making the inside_mesh module work as a standalone one for using the check_mesh_contains method