An Algorithm for Identifying Convexity-Concavity of A Simple Polygon

Based on constructing convex-polygon by extremity vertices and computing cross-products of polygon's edge vectors, an algorithm for automatic identifying the orientation, convexity-concavity of a simply polygon is proposed. The algorithm avoids wrong identification of orientation and convexity-concavity of polygon caused by the misleading property of extremity vertices. It is very simple, straight forward and highly efficient. The complexity of its computing time reaches O(n).