This was a little test project I made to experiment with cellular automata.
Simplex noise can be a very useful tool for accomplishing the same result, but it’s nowhere near as customizable (or fun) as cellular automata.
Here is how it works (i had a rough idea of how this works beforehand but this is for those who might be interested):
1. Create a 2d grid of tiles. turn roughly 50% of them red, at random. Depending on the rules you choose for the cellular automata, you may need to tweak this to be closer to 40% or 60%.
2. Decide on the rules you want to use for each tile. To make this a little easier to understand, imagine that each tile is a living organism like bacteria or something. The organism will either die or expand to other tiles based on its rules. The classic “5-4” rule is as follows: a white tile becomes red if 5 or more of the 8 tiles surrounding it are red. A red tile becomes white if less than 4 of the tiles around it are red. We are basically saying: a bacteria starves to death if it is surrounded by less than 4 other ones, and an empty space spawns a new bacteria if it is surrounded by at least 5 others.
3. Apply the rules to each tile. In order to get desirable results, these rules need to be applied several times in a row. Over time, the cells will shift into a random, unique shape based on the rules you applied in each iteration.
That’s it. The above image is what i got from applying the 5-4 rule 5 times in a row to a grid of 50% white and red tiles.
…But it gets more interesting. We can change the rules to get vastly different results. We can also use different rules with each iteration. For example, we could apply a given rule 3 times, then change the rules and apply the new set of rules 5 times in order to get a totally unique result. The image in the bottom right shows some of the stuff i ended up with using different rule sets. You will also get different results depending on how many iterations you do. There’s an infinite amount of combinations of rules and iterations you can do which makes this a very cool method to use for generating worlds.
In my situation, i wanted to generate a world where there is only one main area (ie, no smaller disconnected white areas that can’t be reached from the main white area). In order to do this i have to first generate the world, then check each white area using a flood fill algorithm (kind of like the bucket fill tool in mspaint) to see what percentage of space in the world each area takes up. In the bottom left you can see this in action. The blue area is the main area and the green areas are the smaller detached areas we want to get rid of. The blue area takes up roughly 40% to 60% of the world space so it is easy to tell which ones are small and need to be discarded (the green ones). In the case that the main area takes up less than 40% of the grid we can always just scramble the grid and start over.
The most popular use of cellular automata is conway’s game of life. Check it out if you wanna play around with this stuff in your browser.
If you are interested in programming something using cellular automata, this page is extremely helpful.