    lineWidget = vtkLineWidget()
    lineWidget.SetResolution(numOfStreamLines)
    lineWidget.SetInputData(pl3d_output)
    lineWidget.GetPolyData(seeds)
    if illustration:
        lineWidget.SetAlignToNone()
--
    lineWidget2 = vtkLineWidget()
    lineWidget2.SetResolution(numOfStreamLines)
    lineWidget2.SetInputData(pl3d_output)
    lineWidget2.GetPolyData(seeds2)
    lineWidget2.SetKeyPressActivationValue('L')
    lineWidget2.SetAlignToZAxis()
