How do I remove self-intersecting triangles from a 3D surface mesh?

问题

I have a CGAL surface_mesh of triangles with some self-intersecting triangles which I'm trying to remove to create a continuous 2-manifold shell, ultimately for printing.

I've attempted to use remove_self_intersection() and autorefine_and_remove_self_intersections() from this answer. The first only removes a few self-intersections while the second completely removes my mesh.

So, I'm trying my own approach - I'm finding the self-intersections and then attempting to delete them. I've tried using the low level remove_face but the borders are not detectable afterwards so I'm unable to fill the resulting holes. This answer refers to using the higher level Euler remove_face but this method, and make_hole seem to discard my mesh entirely.

Here is an extract (I'm using break to see if I can get at least one triangle removed, and I'm just trying with the first of the pair):

    vector<pair<face_descriptor, face_descriptor> > intersected_tris;
PMP::self_intersections(mesh, back_inserter(intersected_tris));
for (pair<face_descriptor, face_descriptor> &p : intersected_tris) {
    CGAL::Euler::remove_face(mesh.halfedge(get<0>(p)), mesh);
    break;
}

Here is an example of the output before I try to remove self intersections.

回答1:

My approach to removing self-intersecting triangles is to aggressively delete the intersecting faces, along with nearby faces and fill the resulting holes. Thanks to @sloriot 's comment I realised that the Euler::remove_face function was failing due to duplicate faces in the set returned from both the self_intersections and expand_face_selection functions.

A quick way to remove duplicate faces from the vector result of those two functions is:

std::set<face_descriptor> s(selected_faces.begin(), selected_faces.end());
selected_faces.assign(s.begin(), s.end());

This code converts the vector of faces into a set (sets contain no duplicates) and then converting the set back again.

Once the duplicates were removed, the Euler::remove_face function worked correctly, including updating the borders so that the triangulate_hole function could be used on the result producing a final surface with no self-intersections.

来源：https://stackoverflow.com/questions/52730931/how-do-i-remove-self-intersecting-triangles-from-a-3d-surface-mesh