Unexpected cleaning result

[MarcelHeu]

Hey,

I try to repair the following mesh (a dental bridge):

Within the mesh are some holes and also intersecting triangles. I use the function tin.small_boundaries() and if i detect intersecting triangles also tin.clean(max_iters=10, inner_loops=3). Unfortunately, the dental bridge is split, leaving only one tooth in the end:

Do you maybe have some ideas how i can fix this issue? You can find the used source code and the *.stl file below:
ScriptAndModel.zip

# -*- coding: utf-8 -*-
import pymeshfix



def plotMesh(tin):
    
    # return vertices and faces
    vertices, faces = tin.return_arrays()
    
    # Create object from vertex and face arrays
    meshfix = pymeshfix.MeshFix(vertices, faces)

    # Plot input
    meshfix.plot()





# Create TMesh object
tin = pymeshfix.PyTMesh()

# load stl file
tin.load_file("bridge08.stl")

# visualize input Mesh
plotMesh(tin)



###############################################################################
# CLEANING ROUTINE

# Attempt to join nearby components
# tin.join_closest_components()

# Fill holes
tin.fill_small_boundaries()
print('There are {:d} boundaries'.format(tin.boundaries()))

# check for intersecting triangles
faces = [tin.select_intersecting_triangles()]

# if intersecting triangles are detected within the mesh
if faces:
    # Clean (removes self intersections)
    tin.clean(max_iters=10, inner_loops=3)
###############################################################################



# visualize output Mesh
plotMesh(tin)

[akaszynski]

Got it partially working:

First, split the mesh into the three individual bodies. They're not connected at all.

import pymeshfix
import pyvista as pv

# we're going to subdivide, for whatever reason this helps meshfix
mesh = pv.read("bridge08.stl")
sub_div = mesh.subdivide(1)

bodies = pv.MultiBlock([body.extract_surface() for body in sub_div.split_bodies()])
bodies.plot(multi_colors=True)

Next, let's join the first and last body (the teeth I'm assuming?)

# join the bodies within pyvista
joined = bodies[0].boolean_union(bodies[2])
bodies[1] = bodies[1].compute_normals(flip_normals=True)
final = joined.compute_normals(auto_orient_normals=True).clean()

# clean
tin = pymeshfix.PyTMesh()
tin.load_array(final.points, final.faces.reshape(-1, 4)[:, 1:])
tin.clean()
mfix = pymeshfix.MeshFix(*tin.return_arrays())
mfix.plot()

The hard part is now the dental bridge. I'm not able to get pyvista to merge it using any boolean_* filter, nor will pymeshfix accept it; it keeps removing it and using join_closest_components just isn't working. I'm a bit at a loss how to proceed. There might be a way to do this by manually dropping faces from the "bridge" (bodies[1]), as I think PyVista and meshfix really don't like how that surface is configured as it sorta wraps in on itself:

bodies[1].plot_normals(mag=0.1)

I hope at least helps you out a bit!

[MarcelHeu]

Thank you, this is helping me a lot! I now have a better understanding of why it doesn't work well.