    volume_scalar_opacity = vtkPiecewiseFunction()
    volume_scalar_opacity.AddPoint(0, 0.00)
    volume_scalar_opacity.AddPoint(500, 0.15)
    volume_scalar_opacity.AddPoint(1000, 0.15)
    volume_scalar_opacity.AddPoint(1150, 0.85)

--
    volume_gradient_opacity = vtkPiecewiseFunction()
    volume_gradient_opacity.AddPoint(0, 0.0)
    volume_gradient_opacity.AddPoint(90, 0.5)
    volume_gradient_opacity.AddPoint(100, 1.0)

    # The VolumeProperty attaches the color and opacity functions to the
--
opacityFunction = vtk.vtkPiecewiseFunction()
opacityFunction.AddPoint(drange[0], 0.0)
opacityFunction.AddPoint(drange[1], 1.0)

# Create transfer mapping scalar value to color.
colorFunction = vtk.vtkColorTransferFunction()
--
    alphaChannelFunc = vtkPiecewiseFunction()
    alphaChannelFunc.AddPoint(0, 0.0)
    alphaChannelFunc.AddPoint(50, 0.05)
    alphaChannelFunc.AddPoint(100, 0.1)
    alphaChannelFunc.AddPoint(150, 0.2)

--
    opacityTransferFunction = vtkPiecewiseFunction()
    opacityTransferFunction.AddPoint(20, 0.0)
    opacityTransferFunction.AddPoint(255, 0.2)

    # Create transfer mapping scalar value to color.
    colorTransferFunction = vtkColorTransferFunction()
