Extensions: 1
PhD Applied Math, Cambridge University, U.K. Erstwhile Professor of Math and Computer Science (ASU, Colorado School of Mines, KAUST) Research Groups at Shape Data Ltd (CAD/CAM), SGI part of OpenGL group). Since retiring, I have been getting up to speed on SketchUp and developing some plugins, using my interest and background in computer graphics and geometry. SketchUp has a great UI and model support. I am enthused about extending it, mainly through geometry.
Design your terrain with simple ridge and valley lines. Standard SU interface -- lines and Bezier.