World Machine v1.0 is a Terrain Generation & Editing package that has become very popular for game development purposes. There is a free Basic Edition available for non-commercial use, as well as a $40 Standard edition that can be used commercially. The website is: features are:Powerful and flexible terrain generation, including "World Class" natural erosion features. Graph based terrain building and realtime 3D Previews for rapid experimentation Explorer Mode. Fly / Drive and Walk around the boundless virtual world defined by the terrain generators.