Hexmap Terrain Generator

 

I was thinking about Traveller subsector generation, and how you could use a similar system to generate settlements and other sites in a region of a fantasy world. Well, first you would need a system to generate the region's terrain. So that's what I made.

I worked with the assumption of 12 mile hexes, but I'm sure anything from 5 to 30 miles is plausible.

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GENERATE YOUR HEXMAP TERRAIN IN 15 EASY STEPS

1. Start with a 10 by 10 hexmap. All hexes are plains.

2. 1d6-2 edges of the map are ocean. Randomly determine which ones. Every hex on these edges is ocean.

3. Every hex bordering an ocean hex has a 3 in 6 chance to be ocean.

4. Every hex bordering one of these secondary ocean hexes has a 2 in 6 chance to be ocean, unless it has already been rolled for.

5. Place 1d6 mountain hexes. Roll two d10s for each to determine its coordinates. If you end up in an ocean hex or a previous mountain hex, roll again.

6. Every plains hex adjacent to a mountain hex has a 4 in 6 chance to be mountains as well; otherwise, it is hills.

7. Repeat step 6, but now with a 2 in 6 chance.

8. Every plains hex now adjacent to a mountain hex is hills.

9. Every plains hex adjacent to a hill hex has a 3 in 6 chance to be hills.

10. Roll 1d6 to determine how many major rivers there are: 1 none, 2-4 one, 5 two, 6 two rivers joining into one. Each river has a 3 in 6 chance to be flowing out of a mountain or hill hex; otherwise, it enters from the edge of the map (if there is a land edge). If there is an ocean on the map, the rivers will flow into it. Draw the rivers using your best judgement (there isn’t an easy way to randomize this). Remember that rivers go downhill: from mountains to hills to plains, not the other way.

11. Decide if the wind blows from west or east. Imagine that rain clouds rise from every ocean hex (or from outside the map) and follow the wind in straight horizontal lines, but are blocked by mountains. Any hex that gets no rain is dry steppe or dry hills, except if it has a river.

12. Every hex with a river has a 3 in 6 chance to be forested.

13. Every hills or plains hex without a river that isn’t dry or next to a dry hex has a 1 in 6 chance to be forested; 2 in 6 if it is next to a forested river hex.

14. Every ocean hex has a 1 in 6 chance of having a small island.

15. Your region is finished!

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I realize now that I didn't put in a way to get swamp hexes, probably because I don't like swamps. Maybe a 1 in 6 chance on every flat river hex that isn't next to a dry hex?

Here's a few regions I rolled up in Worldographer to test the generator out. I like them! The regions can get pretty different, and there's a certain rugged feel to them.

 

Next step, actually making the settlement generator...