Compositing in 3D Space with Action > About Lights and Lighting Effects > Modifying Surface Lighting >

# Flipping a Surface's Normals

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:

1. Add a surface and a light source.
2. In the Light menu or the Rendering section of the Action Setup menu, enable Shading.
3. Copy the surface and its axis in Schematic view. See Mimicking, Copying, and Duplicating Objects.
4. Select the surface of the copied branch.
5. In the Surface menu, enable Flip Normals.

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.