Function _hemi_morph

mne/morph.py:1227–1261

(tris, vertices_to, vertices_from, smooth, maps, warn)

def _hemi_morph(tris, vertices_to, vertices_from, smooth, maps, warn):
    _validate_type(smooth, (str, None, "int-like"), "smoothing steps")
    if len(vertices_from) == 0:
        return sparse.csr_array((len(vertices_to), 0))
    e = mesh_edges(tris)
    e.data[e.data == 2] = 1
    n_vertices = e.shape[0]
    e += _eye_array(n_vertices, format="csr")
    if isinstance(smooth, str):
        _check_option("smooth", smooth, ("nearest",), extra=" when used as a string.")
        mm = _surf_nearest(vertices_from, e).tocsr()
    elif smooth == 0:
        mm = sparse.csc_array(
            (
                np.ones(len(vertices_from)),  # data, indices, indptr
                vertices_from,
                np.arange(len(vertices_from) + 1),
            ),
            shape=(e.shape[0], len(vertices_from)),
        ).tocsr()
    else:
        mm, n_missing, n_iter = _surf_upsampling_mat(vertices_from, e, smooth)
        if n_missing and warn:
            warn_(
                f"{n_missing}/{e.shape[0]} vertices not included in "
                "smoothing, consider increasing the number of steps"
            )
        logger.info(f"    {n_iter} smooth iterations done.")
    assert mm.shape == (n_vertices, len(vertices_from))
    if maps is not None:
        mm = maps[vertices_to] @ mm
    else:  # to == from
        mm = mm[vertices_to]
    assert mm.shape == (len(vertices_to), len(vertices_from))
    return mm


@verbose