_incremental KeyError

[jiapei-nexera]

It looks in function _incremental of file https://github.com/yuehaowang/convex_hull_3d/blob/master/convex_hull.py, there is a bug around is_visible = vol < 0 ??

✗ python convex_hull.py --file ....../MySTL.STL --vis 

Loaded mesh file ....../MySTL.STL
#vertices: 1788
#faces: 1184
Is edge manifold: True
Is self-intersecting: True
Is watertight: False

Computing convex hull...
WARNING: coplanar tetrahedron (2-3-4-1)
WARNING: coplanar tetrahedron (1-3-4-2)
WARNING: coplanar tetrahedron (1-2-4-3)
WARNING: coplanar tetrahedron (1-2-3-4)
  0%|                                                                                                                                                                                | 0/1783 [00:00<?, ?it/s]WARNING: edge(3-165): non-manifold edge
WARNING: edge(2-165): non-manifold edge
WARNING: edge(3-165): non-manifold edge
WARNING: edge(2-165): non-manifold edge
WARNING: edge(3-165): non-manifold edge
WARNING: edge(2-165): non-manifold edge
WARNING: edge(3-165): non-manifold edge
WARNING: edge(2-165): non-manifold edge
 11%|█████████████████▍                                                                                                                                                 | 191/1783 [00:00<00:00, 20605.26it/s]
Traceback (most recent call last):
  File "....../convex_hull_3d/convex_hull.py", line 193, in <module>
    convhull = ConvexHull3D(np.asarray(mesh.vertices), show_progress=True)
  File "....../convex_hull_3d/convex_hull.py", line 42, in __init__
    self._incremental()
  File "....../convex_hull_3d/convex_hull.py", line 120, in _incremental
    elif visible_ls[edge.adj_faces[0]] or visible_ls[edge.adj_faces[1]]:
KeyError: '3-157-165'

[yuehaowang]

It seems this issue is due to the first 4 vertices of the input are coplanar. The incremental convex hall algorithm requires a non-coplanar tetrahedron initialization. I simply choose the first 4 vertices in the input model for initialization (see here). To bypass this issue, I suggest to shuffle the input vertices to make the first 4 vertices non-coplanar.