Resources for determine how climate will shift over a map

So I’m trying to generate a map for my fantasy world, the roadblock I’m kinda stuck on is that I want to have a desert present on this map. However Fractal Terrains isn’t quite generating what I want. It seems like I’m probably going to need to just paint the climates I want manually which is fine, however I still want them to be somewhat realistic in their placements. Does anyone have any videos or good sources for how/where to place specific climates/biomes on a map? I do own the Tome of ultimate mapping and the One Day world builder guides if anyone has some good reference points in there, and especially youtube videos would be super helpful if you know of any good ones.

Thanks for all your help.


  • jslaytonjslayton Moderator, ProFantasy Mapmaker

    FT's climate generator has a significant flaw in that it doesn't model heat or moisture flow in the atmosphere and oceans, meaning that deserts are unlikely to appear in the default configuration.

    A search for "biome distribution follows a pattern based on" turned up 8.1: Climate and Biomes - Biology LibreTexts and it has the classic diagram of atmospheric circulation that shows the atmospheric bands that are the primary drivers of deserts and rainforests as well as has a good discussion of rainshadow deserts. FT's landmasses tend to be very large and would suffer from a third kind of desert (land too far from an ocean to get any rain), but the lack of an atmospheric circulation model won't allow that kind of thing to happen. The page there has a lovely Whittaker diagram at the top that shows how average annual temperature and rainfall combine to give a good approximation of the expected biome: FT's "climate model" is centered around this and its Image Climate coloring has what amounts to an interactive Whittaker diagram that you can color with an arbitrary image.

    I recommend manually painting rainfall downward and temperature upward to get the desired area of climate rather than just using the climate painting tool directly because the climate painter gets blocky edges on the drawn areas and whatever you paint in the climate area doesn't affect temperature or rainfall.

    A note on terminology: FT incorrectly uses the term "Climate" when it should have used "Biome", which can make things more difficult to search for than they should be. This error happened because there had been plans for letting users roughly paint in a map and then let the software fill in the details, but I let that idea creep into the biome area (the Whittaker diagram doesn't have "Mountains", "Hills", or "Bar Rock", for example) because it made the programming more convenient. Unfortunately, that muddled up the user experience and fixing it isn't trivial. Image Overlays provided a better vehicle for Simple Create mode than the original "mash it all together and call it climate", but FT is left with a whole lot of incorrectly-named and otherwise misplaced concepts that would be very difficult to remove.

    Royal ScribeDon Anderson Jr.LoopysueAlex Adams
  • Awesome thanks so much! I’ll read over that tonight at work and try to implement some stuff when I get home.

    also yeah I realized as I was typing this post up that Climate was definitely the wrong term and I should be using biome. But then I started second guessing myself and thinking I was the one who was wrong lol

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