PLANE CONVEX QUADRILATERAL SURFACE
Definition
A <PLANE CONVEX QUADRILATERAL SURFACE> is a <BOUNDED FINITE SURFACE> and a <FACETED PLANE SURFACE PRIMITIVE>; its boundary consists of 4 straight edges connecting 4 vertices; no three vertices are co-linear; if the edges are ordered and assigned directions to form a loop, then the normal given by the vector product of succeeding edges has the same direction at each vertex