Hi, by chance I found this paper:
"Topologically consistent 3D city models obtained by extrusion" Hugo Ledoux and Martijn Meijers, 2010 Delft University of Technology (OTB-section GIS Technology) http://www.gdmc.nl/ledoux/pdfs/_10ijgisextrusion.pdf Interesting and using GRASS! Markus _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user