Starting Xenos

With project Xenos being in full-scale development for three weeks already, I figure it’s time to write something about it. Maybe if I show this page to enough people, someone will actually read it (and maybe even – gasp – become interested in my game). So, what did Xenos become after first three weeks?

I decided to start with one of the harder features of the game – procedural generation of game maps. Starting with difficult parts seems a good strategy: I’d rather fail now, than after I spend months on stuff that wouldn’t work anyway. And the fact that generation algorithms are really interesting to code is purely coincidental, trust me!

My first generator simply sprinkled some random tiles around the map. This was just to test the fact that I had a map, and could display it and scroll around. Then I went to more advanced solution: the L-System.

L-Systems are a well-known concept, widely used to generate natural-looking plants and buildings. Although Wikipedia article seems pretty intimidating, actually L-systems are not that hard – at least, the one that Xenos uses. Basically, what I did was this: imagine some code that takes a rectangular area on map, and creates something inside. Some trees, for example. Let’s call it something-generator. Then, what if you want to create several something-s, arranged in some way? The L-system solves this with code, that takes a (bigger) rectangular area, splits it in some way, and then feeds the resulting parts into something-generator. Voila – several something-s. This is one of the fundamental actions in an L-system – split, then generate. There’s also another one: imagine that you have two different something-generators, and want to choose one of them randomly. To solve this, an L-system has code that takes an area, and then feeds it to another generator, chosen randomly, or maybe based on some criteria.

Now, these two operations – split and choose – don’t seem all that powerful. The real power comes from the fact that they can be combined! To generate a game location, we can split it into several areas, and feed each into a random selector, that then feeds each part into another split, etc, etc, until we get to the bottom and finally put something on the map.

Here’s how it all worked out for Xenos – with pictures!


Simplest building block: fill area with floor tiles

This is the basic “something generator” of the system: just fill the area with floor tiles. Doesn’t look all that interesting. Let’s split it!

Split into walls and floor

In this picture, I’ve split starting rectangle into four “sides” and an “interior”, and then fed three of the sides into wall creator. And I get something like a house…

More splits: and we have rooms and doors

Split it further – in two halves to make rooms. Then split two of the walls in a random point – insert doors. OK, now it’s definitely a house.

Adding more and more in this manner, I combine lots of elements to achieve this:


The whole village! (Click for larger version)

This is where I stand after 3 weeks of development. I haven’t mentioned in this post the time it took me to make all the textures and models for this… as you can see in the screenshots, I’m a lousy artist. And I intend to write another post on creating tools and editors for all this stuff, which actually took me longer then the L-system itself, but would save me a lot of effort in the long run. But this post is too long as it is, so… until next time? And remember, tell all you friends about Xenos. It’s gonna be awesome!


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