The attached patch (against the mp branch) replaces the current approach of the multipolygon code (just connecting the inner and outer ways, thus forming polygons with overlapping segments) by a decomposition approach: The "polygon with holes" is decomposed into "simple" polygons without holes. To make the further development easier, I have put the decomposition code into a separate class PolygonDecomposer. The decomposition code does not yet handle all possible cases - it just cuts off a quadrilateral for each inner way (which is not much different from the old approach) and does not yet check wether this quadrilateral contains or intersects any of the other holes.It should, however, already work for "normal" cases where the holes are not too complex. Best wishes Christian