def centerOfMass(self):
        """Get the center of mass of actor.

        .. hint:: |fatlimb| |fatlimb.py|_
        """
        cmf = vtk.vtkCenterOfMass()
        cmf.SetInputData(self.polydata(True))
        cmf.Update()
        c = cmf.GetCenter()
        return np.array(c)