All World-Building is Modeling
First, I want to propose that all world-building is model building. When I say “model” you may think of something technical, like a climate model running on some super computer. But there are many kinds of model. They can indeed be mathematical, but can also be purely mental, drawn on paper, or made of clay. A model is really just a (theoretical) understanding of a system.
For world-builders who work upwards, from physical detail to people, there comes a phase in every project when you have to worry about climate: the long-term patterns in weather that will matter to the civilizations of your world. This article is a practical guide to getting yourself a decent, believable climate without enormous amounts of work. You can consider this a first-order approximation of climate; there are many ways to add more detail and realism, and I’ll point some of these out as we go. I often do world-building with the computer, but here I’ll mostly talk about drawing on a paper map, for simplicity.
Computer generated terrain usually begins with a base of random noise, or perhaps a fractal. These look nice in small sections, but are unconvincing for a continent: noise has none of the major features it should, like mountain ranges, and fractals are nothing but feature -- they're too regular. Here's a method for generating continent-level trerrain using distortion fields.
To many, the most perfect shape is the circle -- emblematic of unity -- or the square -- for combining with itself in a tile. But in the city Pherasa, the people have long held the spiral above all other forms. For them it is the basis of all aesthetics, and used in architecture, art, religion and war.
The systems of coinage used in the middle ages were more complex and more interesting than what's presented in most fantasy role-playing systems: if gold, silver and copper "pieces" with nice metric conversions seemed too neat to you, you were right; read on.
So you've laced your boots, strapped on your scabbard, and set your jaw. You're ready for some adventure. Where though will you go to find it? Where are the lonely places, where monsters, treasure and glory can be claimed? In this quest, you face some problems.
What business do a man, an elf, and a dwarf have traipsing the countryside looking for quests? Where do they come from, and how do they fit into their society? Can they exist at all? I'll give a few answers to these questions below.
The stock fantasy world of role-playing is, we usually think, basically like medieval Europe. There are castles, swords, peasants; various set pieces. But what do these worlds of abundant cash, swords for hire, open-minded villagers, and "mage guilds" really have to do with the middle ages?
Here I present a surprisingly easy way to fill valleys in a rasterized elevation map, for the purpose of creating realistic rivers quickly.