Hi,As the forum seems so quite, here is something that I am planing to add to SBuilder (SB) when I finish my current scenery project (in addition to support BGLCOMP).In SB data representation I will treat polygons just as lines. At the moment a line is set of 2 double precision numbers (lat and lon) and a single precision number (the width of the point). On the contrary, polygons are sets of 2 double precision numbers (lat and lon). I will add a 3rd parameter to be altitude. I plan to keep the SB interface almost untouched. When I right click a point of a polygon to access to its properties, the "Width" box is disable (greyed). This box is enabled when I access the properties of a point in a line. The first change will be the box to read "Altitude" in the case of polygons and to be enable to accept altitudes.Another change will be in the properties of LWM "water" and "flatten" polygons. Presently there is only a box labelled "Altitude". I plan to add a command but suggestions are welcome. The command would have a label like "Make Complanar" or something more elegant and precise. The operation of the command (algorithm) would be the following:If there is a single point in the polygon with Hmax and there is a single point in the polygon with Hmin then a slopped polygon will be created. Otherwise all points will be given the altitude value that exists in the Altitude box.Note that if I do not press the "Make Complanar" all the previous individual altitudes are retained.If there is only ONE point Pmax and only ONE point Pmin, I define the slopped plane that contains these 2 points. Then I project vertically all the remaining points of the polygon on that slopped plane and I update the altitude of these remaining points with the altitude of the projected points on the referred to plane.I wonder if there is a more intuitive interface for dealing with slopped planes. My idea came from rivers made with LWM water. In the sea they have 0 altitude but, even without dams, the altitude should be greater when we go to the source. So I set the altitude of the LWM river to be 5 meters. Then I pick a point near the sea and give it altitude zero. Then I pick up a point some 50 km inwards and give it altitude 10. Then I press "complanar" or whatever and I have a river descending to the sea.Sorry for thinking loud ...Regards, Luis

Hi,You can test a working version that works with tilted LWM masks. You can get an EXE here (you should have 2.02 set before getting this EXE):http://www.ptsim.com/forum/topic.asp?TOPIC_ID=299Regards, Luis