Flipping a Surface's Normals

3D Compositing with Action > Action: Lights > Modifying Surface Lighting >

When you flip a surface's normals, light is applied to the opposite side of a surface. Use this feature to create a two-sided shaded surface.

To create a two-sided surface:

Add a surface and a light source.
In the Light menu or the Rendering section of the Action Setup menu, enable Shading.
Copy the surface and its axis using the branch option in Schematic view. See Copying Objects.
Select the surface of the copied branch.
In the Surface menu, enable Flip.

To control both surfaces, parent them by a new axis and use this axis to rotate, scale, shear, and move the two surfaces. There may be a priority problem causing one surface to be drawn over the other. To correct this problem, use the Priority Editor to animate the drawing priority of surfaces or change the Z position of one surface by one pixel. See Reordering Surfaces.