elrond@titan.tsd.arlut.utexas.edu (Brad Hlista) (02/25/90)
I have two regions A and B defined by four vertices. Letting A be the boundary of the screen, I am looking for a fast clipping routine to find the new vertices of A intersect B. I have come up with something but the number of tests I make to check the new points continue to grow. I should mention that the vertices of B can be anywhere in the cartesian plane and that none of the lines from the vertices intersect other than at the vertices. Any help would be appreciated. Brad Hlista elrond@titan.tsd.arlut.utexas.edu
spencer@eecs.umich.edu (Spencer W. Thomas) (02/26/90)
In article <610@titan.tsd.arlut.utexas.edu> elrond@titan.tsd.arlut.utexas.edu (Brad Hlista) writes: > I have two regions A and B defined by four vertices. Letting A be the > boundary of the screen, I am looking for a fast clipping routine to find the > new vertices of A intersect B. If A is convex, then you can use the Sutherland-Hodgman polygon clipping algorithm (see any standard graphics text, e.g. Rogers, _Procedural Elements of Computer Graphics_, McGraw Hill). Note that the result may have more than 4 vertices (it can have more than 8, but must have less than 12). If A is concave, then you have to use a more complex algorithm (e.g., Weiler-Atherton polygon clipper, also described in Rogers, and also referenced recently in this newsgroup.) -- =Spencer (spencer@eecs.umich.edu)