I want a python script that can join all the touching meshes in a collection automatically

Question

I have a collection of over 2000 small meshes. I want to automatically have them joined in case meshes touch each other. So, after running python code, I want to end up with fewer meshes.

I tried the following script (chatGPT):

import bpy

# Get a list of all the meshes in the scene
meshes = bpy.data.meshes

# Loop through each mesh
for mesh in meshes:

    # Create a list of all the other meshes that are touching this mesh
    touching_meshes = []
    for other_mesh in meshes:
        if mesh != other_mesh:
            for edge in mesh.edges:
                if edge.vertices[0] in other_mesh.vertices or edge.vertices[1] in other_mesh.vertices:
                    touching_meshes.append(other_mesh)
                    break

    # Join this mesh with all the other touching meshes
    for other_mesh in touching_meshes:
        bool_modifier = mesh.modifiers.new('bool', 'BOOLEAN')
        bool_modifier.object = bpy.data.objects[str(other_mesh.name)]
        bool_modifier.operation = 'UNION'
        bpy.ops.object.modifier_apply(modifier=bool_modifier.name)

but I get this error :

Python: Traceback (most recent call last): File "C:\Users\bartdh\AppData\Local\Temp\7zOC3093EA1\TsD0209-2.blend\Text.001", line 14, in TypeError: bpy_prop_collection.contains: expected a string or a tuple of strings

Thank you for any help.

Answer 1

This will operate on all selected objects (see the commented line if you want to operate on everything in a collection instead).

import bpy
import bmesh
from mathutils.bvhtree import BVHTree

if bpy.context.mode != 'OBJECT':
    bpy.ops.object.mode_set(mode='OBJECT')

# Use all selected objects
obs = list(bpy.context.selected_objects)
# Uncomment this to use all objects from a collection instead
#obs = list(bpy.data.collections["Collection"].objects)

obs = [ob for ob in obs if ob.type == 'MESH']

# Calculate BVHTrees for each object
# Adjust epsilon to change how strict "is touching" is
trees = []
for ob in obs:
    # Can't use BVHTree.FromObject, it doesn't use world space, see
    # devtalk.blender.org/t/bvhtree-fromobject-blender-2-8-wonkiness
    # Instead convert to BMesh and use that.
    bm = bmesh.new()
    bm.from_mesh(ob.data)  # Note: this is the unevaluated mesh
    bm.transform(ob.matrix_world)
    trees.append(BVHTree.FromBMesh(bm, epsilon=0.0))
    bm.free()

# Compute pairs (i,j) where obs[i] touches obs[j]
intersections = []
for i in range(0, len(trees)):
    for j in range(i + 1, len(trees)):
        if trees[i].overlap(trees[j]):
            intersections.append((i, j))
    trees[i] = None  # can GC this now

# Group into connected pieces
pieces = []
for i, j in intersections:
    pi, pj = None, None
    for index, piece in enumerate(pieces):
        if i in piece: pi = index
        if j in piece: pj = index
    if pi is None and pj is None:
        pieces.append(set([i, j]))
    elif pi is None:
        pieces[pj].add(i)
    elif pj is None:
        pieces[pi].add(j)
    elif pi != pj:
        pieces[pi].update(pieces[pj])
        del pieces[pj]

# Join all objects in each piece
for piece in pieces:
    bpy.ops.object.select_all(action='DESELECT')
    for i in piece:
        obs[i].select_set(True)
    for i in piece:
        bpy.context.view_layer.objects.active = obs[i]
        break
    bpy.ops.object.join()