Merging / joining meshes

How can two overlapping meshes be merged?

The figures and scripts / code snippets below describe the problem I’m trying to solve:

• At each of three points there is a sphere of radius 0.1:
  • Point A: (0, 0, 0)
  • Point B: (1, 0, 0)
  • Point C: (2, 1, 0)

I want to create a mesh that surrounds these three points, something like this:

• The script below uses convex_hull to create a mesh over all A, B and C, but not in a piecewise manner:

from math import pi,ceil
import numpy as np
import trimesh


def generate_sphere_vertices(r, rad=0.1, n=36):
	theta     = np.linspace(0, pi, ceil(n/2))
	phi       = np.linspace(-pi, pi, n)
	x0,y0,z0  = r
	[t,p]     = np.meshgrid(theta, phi)
	phi,theta = t.flatten(), p.flatten()
	x         = x0 + rad * np.sin(theta) * np.cos(phi)
	y         = y0 + rad * np.sin(theta) * np.sin(phi)
	z         = z0 + rad * np.cos(theta)
	return np.vstack( [x,y,z] ).T


vertsA = generate_sphere_vertices( (0,0,0) )
vertsB = generate_sphere_vertices( (1,0,0) )
vertsC = generate_sphere_vertices( (2,1,0) )


verts   = np.vstack( [ vertsA, vertsB,vertsC ] )
pc      = trimesh.PointCloud( verts )
mesh    = pc.convex_hull
mesh.show()

The result looks like this:

To create a piecewise mesh over AB, then BC I tried to use union, as in the script below, but this does not work.

vertsAB = np.vstack( [ vertsA , vertsB ] )
vertsBC = np.vstack( [ vertsB , vertsC ] )
pcAB    = trimesh.PointCloud( vertsAB )
pcBC    = trimesh.PointCloud( vertsBC )
meshAB  = pcAB.convex_hull
meshBC  = pcBC.convex_hull
mesh    = meshAB.union(meshBC)
mesh.show()

The resulting mesh looks the same as meshAB.

Is it possible to join or merge the two meshes?

What is union actually doing?

[0todd0000]

Oops! I just noticed that this question was already answered in #245, sorry about that!

I used:

combined = trimesh.util.concatenate( [ meshAB, meshBC ] )

But I still don’t understand what union is doing in the case above. Why doesn’t union work?

[richardrl]

the concatenate command from above works as expected: