Calculate Union on meshes from meshio

[gatoniel]

Hi,
I hope it is okay to ask for help here. Additionally, I am unsure if this is a replicate of #131

I want to calculate the union of two 3d closed objects defined by triangles. With meshio.Mesh it is super straight forward to create the meshes of these objects. But I cannot pass them to pygalmesh.Union. Is there a way to use pygalmesh.Union on these meshes or how would you proceed? Or is pygalmesh.Union only available for primitive objects like Spheres, etc. (i.e., things that can be represented with _pygalmesh.DomainBase)?

I would like to use this pseudo code:

# verts1, verts2= ...
# faces = ...
mesh1 = meshio.Mesh(
        verts1, [("triangle", faces)]
)
mesh2 = meshio.Mesh(
        verts2, [("triangle", faces)]
)

# do some intermediate stuff to transform mesh1 and mesh2 to correct format, i.e., _pygalmesh.DomainBase

union = pygalmesh.Union([mesh1, mesh2])

This code results in this error message:

TypeError: __init__(): incompatible constructor arguments. The following argument types are supported:
    1. _pygalmesh.Union(arg0: List[_pygalmesh.DomainBase])

Invoked with: [<meshio mesh object>
  Number of points: 96
  Number of cells:
    triangle: 188, <meshio mesh object>
  Number of points: 96
  Number of cells:
    triangle: 188]

If pygalmesh is not the correct choice for this, do you know any other package that can do something like this?

[nschloe]

pygalmesh's Union only works on domains (the geometry, e.g., sphere centered at X with radius R), not meshes. If you already have your mesh, you're out of pygalmesh's domain.

[gatoniel]

Ok, thanks. I thought so already. Do you have any suggestions on how to calculate Unions of predefined meshes? I have three ideas:

1. The discussed ideas in Volume or related statistics of the Intersection, union and difference objects #131 Can you tell me how complicated the PR for this issue is? I can program in Python, but I have never incorporated C functions into python.
2. I convert my predefined meshes somehow back to domains
3. I convert my meshes into voxel images. There I can simply create a union. Then I can simply recreate a mesh based on this voxel representation with https://github.com/nschloe/pygalmesh#meshes-from-numpy-arrays-representing-3d-images

[gatoniel]

Hi,
I found another mesh package: https://github.com/mikedh/trimesh
If blender or openSCAD are installed this package can calculate boolean operations on triangular meshes. This is what I need, so we can close this discussion.
Best,
Niklas