Measure distance between meshes

Question

For my project, I need to measure the distance between two STL files. I wrote a script that allows reading the files, positioning them in relation to each other in the desired position. Now, in the next step I need to check the distance from one object to the other. Is there a function or script available on a library that allows me to carry out this process? Because then I’m going to want to define metrics like interpenetration area, maximum negative distance etc etc so I need to check first the distance between those objects and see if there is like mesh intersection and mesure that distance. I put the url for the combination of the 2 objects that I want to mesure the distance:

https://i.stack.imgur.com/y5hFT.jpg

Answer 1

Pyvista offers a really easy way of calculating just that:

import pyvista as pv
import numpy as np

mesh_1 = pv.read(**path to mesh 1**)
mesh_2 = pv.read(**path to mesh 2**)

closest_cells, closest_points = mesh_2.find_closest_cell(mesh_1.points, return_closest_point=True)
d_exact = np.linalg.norm(mesh_1 .points - closest_points, axis=1)
print(f'mean distance is: {np.mean(d_exact)}')

For more methods and examples, have a look at:

https://docs.pyvista.org/examples/01-filter/distance-between-surfaces.html#using-pyvista-filter

Answer 2

To calculate the distance between two meshes, first one needs to check whether these meshes intersect. If not, then the resulting distance can be computed as the distance between two closest points, one from each mesh (as on the picture below).

If the meshes do intersect, then it is necessary to find the part of each mesh, which is inside the other mesh, then find two most distant points, one from each inner part. The distance between these points will be the maximum deepness of the meshes interpenetration. It can be returned with negative sign to distinguish it from the distance between separated meshes.

In Python, one can use MeshLib library and findSignedDistance function from it as follows:

import meshlib.mrmeshpy as mr
mesh1 = mr.loadMesh("Cube.stl")
mesh2 = mr.loadMesh("Torus.stl"))
z = mr.findSignedDistance(mesh1, mesh2)
print(z.signedDist) // 0.3624192774295807