The Polygon Side node assigns black or white values based on a polygon object's normal direction. This is useful for assigning different textures or materials to different sides of a polygon object. In figure 1, a Polygon Side node is used as the mix amount distributing blue on one side of the polygon object and red on the other.


Nodegraph Layout

Figure 1: A Polygon Side node controls the Mix texture node and the blending amount of blue and red RGB Color nodes