from Red Blob Games
Jul 2018, Apr 2023

Pick a starting seed, then paint mountains, valleys, and oceans on the map! It will simulate evaporation, wind, and rainfall to determine biomes and rivers.


Play with the sliders to change the simulation and style. For example, try decreasing raininess slider to see how reducing rainfall will make rivers dry up, or try decreasing lg_min_flow to see more small streams.

Treat this as a tool. Everything you create with it is yours to do with as you please. Credit is appreciated but not required. Suggested tag: #mapgen4. (doesn’t work on all platforms).

Goals for this project:

Status of the project: Finished, source code available[1], but the project is mostly inactive. I made some code changes in Apr 2023, with slightly higher resolution maps, but the maps won’t exactly match previously generated maps. I have a series of blog posts[2] about how I made these maps:

Also see my project from 2010[14], where I started developing these techniques. There are lots of things that could be added on top of the underlying delaunay+voronoi structure, like towns, trees, biomes, seasons, nations, watersheds, etc. If you’re interested in adding these, take a look at the source code, and feel free to email me. One day I might work on a mapgen5 that explores some more ideas on top of this.

Email me , or tweet @redblobgames, or comment: