Compute border vertices of a label using Rvcg.
label.border.fast(surface_mesh, label)named list with entry 'vertices' containing an integer vector with the indices of the border vertices.
an fs.surface instance, see subject.surface.
an fs.label instance (see subject.label) or an integer vector, the vertex indices of the label.
label.border, which is slower but provides more options and does not require Rvcg.