        picker = vtkPropPicker()
        picker.Pick(clickPos[0], clickPos[1], 0, self.GetDefaultRenderer())

        # get the new
        self.NewPickedActor = picker.GetActor()

--
        picker = vtkPropPicker()
        picker.Pick(clickPos[0], clickPos[1], 0, self.GetDefaultRenderer())
        self.LastPickedActor = picker.GetActor()

        # If we picked something before, remove the silhouette actor and
        # generate a new one.
