Skip to content

non_manifold_edges

non_manifold_edges(F)

Given a triangle mesh with face indices F, returns (unoriented) edges that are non-manifold; i.e., edges that are incident to more than two faces.

Parameters:

Name Type Description Default
F (m,3) numpy int array

face index list of a triangle mesh

 required

Returns:

Name Type Description
ne (n,2) numpy int array

list of unique non-manifold edges. Columns are sorted in ascending index order, and rows are sorted in lexicographic order.

Notes

It would be nice to also have a non_manifold_vertices function that wraps 2D and 3D functionality.

Examples:

from gpy import non_manifold_edges
# bad mesh with one non-manifold edge in [0,2]
f = np.array([[0,1,2],[0,2,3],[2,0,4]],dtype=int)
ne = gpy.non_manifold_edges(f)
# ne is now np.array([[0,2]])
Source code in src/gpytoolbox/non_manifold_edges.py 
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
def non_manifold_edges(F):
    """Given a triangle mesh with face indices F, returns (unoriented) edges that are non-manifold; i.e., edges that are incident to more than two faces.

    Parameters
    ----------
    F : (m,3) numpy int array
        face index list of a triangle mesh

    Returns
    -------
    ne : (n,2) numpy int array
        list of unique non-manifold edges. Columns are sorted in ascending index order, and rows are sorted in lexicographic order.

    Notes
    -----
    It would be nice to also have a non_manifold_vertices function that wraps 2D and 3D functionality.

    Examples
    --------
    ```python
    from gpy import non_manifold_edges
    # bad mesh with one non-manifold edge in [0,2]
    f = np.array([[0,1,2],[0,2,3],[2,0,4]],dtype=int)
    ne = gpy.non_manifold_edges(f)
    # ne is now np.array([[0,2]])
    ```

    """

    assert F.shape[1] == 3

    he = halfedges(F).reshape(-1,2)
    he = np.sort(he, axis=1)
    # print(he)
    he_u = np.unique(he, axis=0, return_counts=True)
    # print(he)
    ne = he_u[0][he_u[1]>2]

    return ne