Could be, but it is not. When I check the point (1 0 0) the result is "true", so 'on-the-edge' is still inside. -- View this message in context: http://vtk.1045678.n5.nabble.com/PointInPolygon-works-strange-tp5721855p5721866.html Sent from the VTK - Users mailing list archive at Nabble.com.