singularity.py 文件源码

def compute_edge_types(machina, edge_index):
    """Classify the internal edges by type, and find the singular graph.
    The edge type is determined by concatenating the matchings around the edges one-ring."""
    # For each internal edge of the tetrahedral mesh.
    for ei in edge_index:
        try:
            one_ring = machina.one_rings[ei]
        except KeyError:
            continue # Not an internal edge.

        # Concatenate the matchings around the edge to find its type.
        edge_type = np.identity(3)
        for fi in one_ring['faces']:
            matching = []
            # Recall that in the one-ring, if 'fi' is negative, it is
            # a 't-s' pair, as opposed to a 's-t' pair.
            # If pair order is reversed, invert/transpose rotation matrix.
            # Use copysign to distinguish +0 from -0.
            if np.copysign(1, fi) > 0:
                matching = chiral_symmetries[machina.matchings[fi]]
            else:
                matching = chiral_symmetries[machina.matchings[-fi]].T
            # Concatenate transforms
            edge_type = np.dot(edge_type, matching)

        # Locate singular (not identity) and improper (not restricted) edges.
        is_singular, is_improper = True, True
        for si, restricted_type in enumerate(chiral_symmetries[0:9]):
            if np.allclose(edge_type, restricted_type):
                if si == 0 : is_singular = False
                is_improper = False
                break

        # Classify as proper(0), singular(1), improper (2)
        if is_singular: machina.edge_types[ei] = 1
        if is_improper: machina.edge_types[ei] = 2