"This article originally appeared in Game Developer magazine, and appears with the permission of Think Services."
Edge detection techniques are fundamental to non-photorealistic rendering algorithms. Two of the fundamental algorithms used in non-photorealistic rendering algorithms are silhouette edge detection and crease edge detection. The silhouette edge is the part of a model where the front facing triangle borders a back facing triangle. A crease edge is found where the angle between two front facing triangles is beyond a certain application-defined threshold.