def index_sparse(column_count, indices):
    """
    Return a sparse matrix for which vertices are contained in which faces.

    Returns
    ---------
    sparse: scipy.sparse.coo_matrix of shape (column_count, len(faces))
            dtype is boolean

    Examples
     ----------
    In [1]: sparse = faces_sparse(len(mesh.vertices), mesh.faces)

    In [2]: sparse.shape
    Out[2]: (12, 20)

    In [3]: mesh.faces.shape
    Out[3]: (20, 3)

    In [4]: mesh.vertices.shape
    Out[4]: (12, 3)

    In [5]: dense = sparse.toarray().astype(int)

    In [6]: dense
    Out[6]:
    array([[1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
           [0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
           [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0],
           [0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0],
           [0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0],
           [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0],
           [0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0],
           [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0, 0, 1],
           [1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0],
           [0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 0],
           [0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 1],
           [0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1]])

    In [7]: dense.sum(axis=0)
    Out[7]: array([3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3])
    """
    indices = np.asanyarray(indices)
    column_count = int(column_count)

    row = indices.reshape(-1)
    col = np.tile(np.arange(len(indices)).reshape(
        (-1, 1)), (1, indices.shape[1])).reshape(-1)

    shape = (column_count, len(indices))
    data = np.ones(len(col), dtype=np.bool)
    sparse = coo_matrix((data, (row, col)),
                        shape=shape,
                        dtype=np.bool)
    return sparse
Return a sparse matrix for which vertices are contained in which faces.

    Returns
    ---------
    sparse: scipy.sparse.coo_matrix of shape (column_count, len(faces))
            dtype is boolean

    Examples
     ----------
    In [1]: sparse = faces_sparse(len(mesh.vertices), mesh.faces)

    In [2]: sparse.shape
    Out[2]: (12, 20)

    In [3]: mesh.faces.shape
    Out[3]: (20, 3)

    In [4]: mesh.vertices.shape
    Out[4]: (12, 3)

    In [5]: dense = sparse.toarray().astype(int)

    In [6]: dense
    Out[6]:
    array([[1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
           [0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
           [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0],
           [0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0],
           [0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0],
           [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0],
           [0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0],
           [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0, 0, 1],
           [1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0],
           [0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 0],
           [0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 1],
           [0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1]])

    In [7]: dense.sum(axis=0)
    Out[7]: array([3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3])