Hi,
please look for mixed technology with "gimp"(hightmap) , "zsurf"(convert to surface) and "moi3d-tools"(manipulate surfaces), but needs a lot of exercise and fun.
........Other special programs for this technology cost a skyscraper.......

http://www.youtube.com/watch?v=U6UWUEM3BPE

http://mwt.net/~sjedging/ZSURF4.zip