Identification of Faces in a 2D Line Drawing Projection of a Wireframe Object

An important key to reconstructing a three-dimensional object depicted by a two-dimensional line drawing projection is face identification. Identification of edge circuits in a 2D projection corresponding to actual faces of a 3D object becomes complex when the projected object is in wireframe representation. This representation is commonly encountered in drawings made during the conceptual design stage of mechanical parts. When non-manifold objects are considered, the situation becomes even more complex. This paper discusses the principles underlying face identification and presents an algorithm capable of performing this identification. Face-edge-vertex relationships applicable to non-manifold objects are also proposed. Examples from a working implementation are given. Index Terms Line drawing interpretation, face identification, line labeling, 3D object reconstruction, non-manifold geometry, image understanding.