Desirability I

Where do people live?

My plan is to set rules to determine a value of desirability. Cities will then be placed at the most desirable locations first, and then less desirable. When I get around to the history simulator, this rating will be used to guide the spread of civilizations. Azgaar has a very nice demonstration of this process here.

The base desirability will be 0.

+1	Coastal hex
+1	Natural harbor (if only one of the hex touches the ocean). I need to think about how I can check for this, since I currently use hex centers and not edges
+1	Per point of river drainage. This might be a little much, since these rivers can get fairly large. The Amazon would, by this system, have a drainage value of about 6800 at its mouth. Predictably then, the city of Belém was the first European settlement on the Amazon
+1	Per number of rivers joining at this point ($n-1$).
+1	Per raw (Stage 0) resource. Some will naturally be worth more than others (gold is better than copper), but overall this will be a good start.
+1	Within a favorable biome. This will capture temperature ranges as well as roughly approximating agricultural potential. It's pretty difficult to find information on specific biome suitability, since mankind is incredibly adaptable. For now, I'll just add this if temperature is between 60 F and 90 F, and if the biome is not E (tundra) or B (desert)
-2	In fact, E or B biomes are likely to be extremely unfavorable to settlement
-1	Mountainous terrain isn't great either

Applying those simple rules yields this:

Desirability map

A few thoughts. First, the rivers are looking very nice. There are some which drain uncermonially into the sea after a few dozen miles, and some which arc across the landscape. This map is set to have no endorheic basins but I'll be changing that, maybe even to the 17% Earth value. Second, the ideal bands are still pretty sharp, and I don't really like that. I have my doubts that wind could push enough moisture to form a rainforest across nearly 6000 miles (bottom right). I might need to further reduce the penalty for the tundra.

However, I just had a thought that if different races prefer different climates, perhaps I could create a different map for each. Everyone likes river trade, but halflings are particularly suited to the cold and so have penalties in warmer climates, whereas orcs are desert dwellers and build their cities in heat that would make an elf weary. Food for thought. The system is extendable and takes very little time to solve - I've vastly improved the brute force algorithms of a few months ago and now changes are easy to make.