An Algorithm for Evaluating the Area of the Overlap or the Union of Polygons

An algorithm for evaluating the intersection or union area of polygons can be implemented by polygon clipping.The main idea in this paper is using polygon lists in Weiler-Atherton's algorithm for polygon clipping.While traversing the list,the algorithm changes direction when it meets the intersection points,then the point-sets of the union of polygons can be obtained.On the other hand,if the algorithm starts traversing from an entry point and changes direction when it meets the points of intersection,the point-sets of the overlap can be obtained. Finally,with the two lists we can evaluate their area.The algorithm can handle general polygons including concave polygons and even polygons with holes inside.