Create a submesh including only the given vertices.
submesh.vertex(surface_mesh, old_vertex_indices_to_use)
an fs.surface instance, the original mesh
integer vector, the vertex indices of the 'surface_mesh' that should be used to construct the new mesh.
the new mesh, made up of the given 'old_vertex_indices_to_use' and all (complete) faces that exist between the query vertices in the source mesh.