HC update #1 : landmass generation

First HC update! I'm working on map generation now, and wanted to write a bit about how I've done landmass generation. I know this has been done a million times already, but I went in blind and didn't look up any common approaches since I found the process of figuring out how to make it work fun, reinventing the wheel or not.


First, here are some generated landmasses:

I like them! Each has character, and will hopefully give rise to interesting storytelling; a mythical monster dwelling in the giant lake of the world on the left, merchant empires operating in the large inland sea of the middle world, or an insular cult occupying the small island of the one on the right.

generation algorithm

Here is how the landmasses are generated:

  1. The map is filled with Ocean terrain
  2. Until enough of the map is covered in land, do:
    1. Pick a random Ocean tile that's not too close to the map's edge
    2. "Flood out" some number of land tiles from it

Pretty simple, right? It gets interesting when you start tweaking some of the parameters. Here are the most important ones:

  • land_total - how much land do we want? I set this to some random fraction of the total number of tiles, within some sensible range (vague words here since I'm still changing this. Let's say it's between 20% and 80%)
  • points - how many flood origin points (step #2.1) to pick. This also affects step #2.2, as the amount of flooding from each point is simply land_total / points
  • expand_chance - how likely is it to "flood" to a neighboring tile


A brief look at how "flooding" works:

  1. create a list all_pos, initially containing the origin point
  2. create a list pos, initially also containing the origin point
  3. create a new list, new_pos, initially empty
  4. go through elements in pos, and look at each element's neighboring tiles
    1. if the tile is not in all_pos, pos, or new_pos, add it to new_pos with chance expand_chance
  5. add all elements in new_pos to all_pos
  6. clear pos and add all elements in new_pos to it
  7. clear new_pos
  8. repeat steps 4-7 until all_pos contains the desired number of elements

parameter influence

Lastly, a bit about how each of the mentioned parameters affects the resulting map:

  • land_total - self-explanatory. Don't want the number to be too high otherwise it's just one large blob with little variety, but also not too little so there's land on which things can happen
  • points - more points make the landmasses more "wiggly" and fragmented... Words are hard, pictures below
  • expand_chance - if this is just set to 1 (aka 100%), the flood just produces a relatively uniform "block", with no interesting edges. Again, pictures below

High points number

points == 1

points == 1 and high expand_chance

For the showcase landmasses shown at the beginning, I used the following values:

  • land_total = area * rand(30%, 60%)
  • points = 20
  • expand_chance = 30%

That's it for now! At the time of writing I'm well on my way to getting various terrains (think biomes) sensibly placed on the generated landmasses, so next update will be about that and hopefully soon.