I tend to lean towards science-fiction and fantasy, so world building matters a lot to me. A while ago, there was a question which asked how to go about organizing your universe, which was interesting, but what I would like to know is: are there tools available that help with the world-building process itself?

I don't just mean from the perspective of just suggesting ideas, but rather would like something from a more science-based perspective. Ideally, I would be looking for a tool that could take data like circumference, moons, distance from the sun, tilt, and so on,and then be able to get data back like gravity, day/night/season/year etc. cycles, the planet's climate, and so on.

If it helps organise that information as well, that would be a bonus, but I don't mind a single, stand-alone tool that focuses specifically on what I'm looking for.

Edit: I've been digging around a bit on Google to see what I could find, and have come across an interesting piece of software called Fractal Terrains from ProFantasy that allows you to randomly generate a world. I've played around with the demo version a little, and you can change things like tilt, average rainfall, greenhouse, and a few other variables, as well as get different maps showing climate, altitude etc., but it doesn't seem to take into account its relationship with any nearby suns, or moons etc., or work out the seasons/cycles.

Still, it's pretty close, and it seems that it can partner with another piece of software they've developed called Campaign Cartographer, which makes the whole package pretty interesting.

However, if anyone else has got something similar to recommend, that would be brilliant.

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    I'm waiting for Lauren Ipsum to pop in and tell us Scrivner does this too. =P Commented Apr 7, 2011 at 13:55
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    LOL Funny, I was thinking the same thing. I better go check their website, just in case ;) Commented Apr 7, 2011 at 14:06
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    Dude, if Scrivener did THAT, I would have finished my novel two years ago. ;) Commented Apr 7, 2011 at 14:10
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    I wonder if we mention Scrivener in enough of these questions if our number of daily visitors will rise... Commented Apr 7, 2011 at 14:52
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    @John: don't tempt me! :) Commented Apr 8, 2011 at 1:29

10 Answers 10


SimEarth might work well for you. As I remember, in addition to the Earth simulation, there was Martian terraforming as well. It is an old DOS game; I wish Maxis had updated it for modern computers.

Something that might also be interesting is EdGCM, the only global climate model I know of that will run on a PC. Changing the forcings in model can provide some interesting effects - global cooling, global warming and so on. For science fiction scenarios set in the distant past, (try the Iceball Earth scenario) an alternate present, or set in the future, it should provide some climate related ideas.

Although they are not software, older RPGs like Traveller and Space Opera included systems for generating solar systems and planets.

For terrain, try VistaPro. Also an older program, it works quickly and can use real-world DEM data (sections of the Earth and Mars are included) or randomly generate landscapes. Try using something like part of the southern US and raise the sea level a hundred feet or so for an interesting effect.

  • DOS game? Just use DOS emulator dosbox.com, works fine on both Windows and Linux. Commented May 21, 2012 at 11:57

My advice? Skip the world building.

Focus instead on your characters. Tell the story as it happens to them. Invent the world around them as you need to in order to tell their story. If you introduce inconsistencies, clean them up in a later draft.

Focusing on the axial tilt of the planet your characters live on rather than who your characters are and what they want is a great way to never get any actual writing done.

  • Big +1 right there. I think the best way is to carve the surroundings out of your character's experiences. Is it cold? Just say "It was cold, a frosty bite to the morning air." rather than, "It was a cold climate. The land masses to the east caused low pressure systems to bring dry cold air from the east, precipating snow and freezing water into ice during the planet's Winter." BORING. Commented Apr 13, 2011 at 23:13
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    @jalefkowit Well, I agree that too much world building isn't a good thing but disagree about just focusing on characters and shaping the world around them. Characters are products of their time and place. If you are unaware of the time or place, you won't have believable characters. @Nick just because I know the finer details of the world, doesn't mean I would ever tell the reader everything, or even tell them in that fashion. Commented Apr 13, 2011 at 23:26
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    Some authors put out guide books to their works as well. That's where you'd list things like solar systems, weather patterns, etc. as well as in-depth character information. Maybe that's Craig's plan. =P Commented Apr 14, 2011 at 0:00
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    @Craig: Perhaps, but placing your characters doesn't require the depth of thought that "world-building" implies. Say you want to tell a story about characters who live on a world where it's always winter. All you need to know to place your characters is that it's always winter. You don't need to figure out WHY until you reach a point in telling the story where the WHY affects the plot.
    – jalefkowit
    Commented Apr 14, 2011 at 14:03
  • @jalefkowit - Sure, that's very true. I suppose I like the fact that world building lets my imagination flow, though. To me, a tool that could randomly generate worlds based on a few scientifically accurate inputs can be a real stimulus to the imagination. I don't see it as a waste, even if much of what I come up with never sees the light of day. It's more creativity I'm after here, prodding me to ask "Why?" and come up with ideas. The best fantasy words I've ever read have had rich, detailed worlds full of depth, and that's a good thing, IMO :) Commented Apr 14, 2011 at 14:23

Regarding climate:

I struggled with climate on a fictional world for a long time. What I eventually realized is that all the climate models we have are generated in reference to a single example. In other words: things like albedo effect, cloud cover, precipitation and seasonal weather patterns are entirely dependent on the specific shape and configuration of the earth's landmasses, it's size, density, orbital characteristics, and the current position of our single, relatively large moon. Change any of those and you radically change the weather systems. Some general rules hold true (like the Coriolis effect), but only the most general. Everything else is interdependent--and interdependent in ways that we don't precisely understand because we only have access to a single reference. So unfortunately, if you want a realistic fictional world that isn't merely an alternate Earth, there are no existing models that are capable of generating even moderately detailed climate systems: you have to figure it out (or make it up) yourself.

Which, of course, isn't necessarily a bad thing.

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    Well, since no-one can actually know how the weather on a different planet (in a different planetary system) is... making it up shouldn't be a problem, since no-one could spot the mistakes (except someone from an identical planet, but...) Cheers. ;-) Commented Apr 8, 2011 at 19:08
  • I think there is also the point that your characters may not know about weather system. It may "snowy, but warm further north" and that's all the reader may care to know. Commented Apr 13, 2011 at 23:10

It is not really software, but a good guide. If you want something to do a lot of it for you, this open source project is a good place to start.

  • Thanks for the info, MaQleod. That guide looks interesting, but is more of a general idea on building fantasy worlds. Unfortunately, that world building tool is a no go. While it looks like it may be what I'm after, it crashes whenever I try and do anything with it. Seems that it's an old project from 2006, so it's probably not supported (I tried different compatibility modes, too, and that didn't work, either). Commented Apr 8, 2011 at 9:42
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    Last update from last June. Okay, it's been awhile, but it's not from 2006 (that's just when it was registered). So, reporting problems may be useful. Commented Apr 8, 2011 at 14:36
  • @jae - Ah okay, sorry, misread that, apologies. I might drop the developer a line and let him know. From what I could tell, I was getting an error because I had a more recent version of a particular driver that the software needed. Anyway, thanks for the heads up! Commented Apr 8, 2011 at 14:43
  • the open source project seems to be made with Visual Studio 6.0 (C++) and crash all the time. While it seems an interesting project, the overall technology chosen is outdated and poorly designed (you can't resize the main window!). Commented Dec 28, 2011 at 7:42

First, as someone who has used world builders extensively, a warning: When you have a hammer, everything looks like a nail.

World builders are all limited to certain things. None are as realistic as they say on the box, and you'll find yourself with a few odd looking flaws which actually damage immersion. I strongly suggest you design your world first and find the mechanics that explain why it works that way instead of rolling a generator and building the story around your results. You'll likely create less scientific flaws than if you ran it through a generator.

But to answer the question, some games do put a lot of focus on world creation. Civilization 5 has a nice system if you want to simulate terrains loosely.

The best so far is Dwarf Fortress. It was designed first-most as a fantasy world simulator, with the game built on top of that. It simulates incredible detail, from boiling points and chemicals to geology. It takes about a week to get past the poor interface. Though it doesn't simulate things like multiple moons and suns yet. There's also good modding capacity if you want to generate something very specific.

To wander a little off topic, Aurora is an incredibly detailed universe creator, which seems to be designed as a sci fi roleplaying game of some sort. It's not a direct world builder, but anyone who appreciates extreme detail and sci-fi worlds might find it useful. On the other hand, it might take around half a month just to learn how it works.

But this also brings up a second warning on world generators: They can be fun/distracting to play with in themselves and the more realistic a simulation is, the more work it takes to learn to use it.


Depending on where you live you might want to consider going to Life The Universe and Everything @ BYU. I've gone to a few and they have an excellent World Building track.

A warning, world building can be so fun that you forget to write your story and that would be a shame.

  • Wow, that looks awesome. Wish I lived on the same continent that's happening. Even has Tracy Hickman ... Weiss and Hickman's Dragonlance novels were one of my first forays into fantasy. /me jealous. Commented Apr 11, 2011 at 20:14

Astronsynthesis is supposed to be good. While it is not world builder software, you might find it a useful helper app for the very big picture.

That site offers Fractal Mapper, as well. However, it is not a simulator or guide.


UniverseSandbox has a relatively new powerful Astrophysics and celestial mechanics simulator if you are writing a Sci-Fi universe and would like something that will give you a chance to make sure your orbits, day/month/year lengths, number of moons, etc are reasonable and workable.

It also has a gross calculation of planetary surface temperatures based on your sun's data and planet's orbit, with configuration for planetary Albedo and Infrared Emissivity.

I think it runs Fractal Mapper or something similar to generate random planetary textures, or you can import your own surface texture map so you can see your world how it might look from space. }}:P


I have used NBOS's Astrosynthesis, and it bridges the gaps the OP spoke of when he mentioned Pro Fantasy's Fractal Terrains. The two actually work in conjunction; with Astrosynthesis allowing for the creation of entire universes — if you were willing to spend that much effort — and Fractal Terrains allowing for the creation of realistic worlds based on planet data generated in Astrosynthesis. Astrosynthesis also fits his bonus criteria of keeping it all organized.


I recommend the book World-Building -- A writer's guide to constructing star systems and life-supporting planets, by Stephen L. Gillett. The author has a PhD in geology, and so he covers topics like plate tectonics, water and air, magnetic fields, colors, etc. The book also covers various aspects of planets and stars, orbits, gravity, seasons and tidal action.

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