code: def centerOfMass(self):
          
          cmf = vtk.vtkCenterOfMass()
          cmf.SetInputData(self.polydata(True))
          cmf.Update()
          c = cmf.GetCenter()
          return np.array(c)
docs: Get the center of mass of actor.
  
          .. hint:: |fatlimb| |fatlimb.py|_