This paper presents an efficient algorithm for extracting faces from polyhedral wireframe models. The main features of the algorithm are using the topological and geometric information of wireframe models and its stronger adaptability. First

the wireframe model is projected to a plane

and the “invisible” edges which are obstructed by another edge in projection are hidden. And the edges which have a common vertex are arranged into a set in counterclockwise. Then search the minimal circle based on rule of the smallest rotation angle in clockwise. At the same time the Moebius rule are use to delete the illegal circle and remove the finished edges which are accurately contained by two circles. When a “visible” edge is removed

“invisible” edges blocked by it may be “visible” ones. So the new minimal circle can be searched. Repeat this course until all edge is removed and there are no illegal circle and illegal edge. Finally，the remaining circle are all true face of the model and all point to outside of the object by adjusting their direction. Several typical examples are given to demonstrate the widespread adaptability and high efficiency of the algorithm.