Quad

= Quad =

A four-sided polygon. Some RT3D engines use quads instead of triangular polygons because it saves NEED DEFINITION, because a square polygon stored as a quad stores only four vertices, whereas a square created with two triangles means transforming six vertices instead of only four. The artist should keep the vertices of the quad coplanar, or rendering weirdness can happen, because the quad is divided into two triangles at render time. The internal edge between the two tris is determined arbitrarily, so it could look like a ridge or a valley.