Voxel water simulation

I am implementing a voxel world for fun, which I tend to do every so often. I want to simulate water in this world, so I started looking into how to do that. Instead of using Minecraft’s water simulation style, in which a single water block can generate seemingly infinite water, I wanted a more realistic simulation where for example mass is conserved and water flows somewhat naturally.

I found this neat 2012 video of simulated water and its related blog post by AlwaysGeeky. Going back further it seems it might have written based on this 2009 2D Processing example, which was originally working online in a Java Applet, but of course that’s not going to work in today’s world. In an attempt to understand how it works, I ported the Processing code into TypeScript.

To go all the way back in the provenance of this, the original idea for performing water voxel simulation using cellular automata was from Tom Forsyth, who wrote an article on this and other clever potential uses of cellular automata in games way back in 2001.

Anyhow, on with the show. Here’s the final version of the water simulation. You can play with the controls and edit the world by drawing on it in the various edit modes. The smoothing factor controls how much the water flow is dampened in the simulation. Near zero, it will flow very quickly but is prone to oscillations. Near one, it will flow very slowly but is more stable.

As you can see, the water falls off the edges and bottom of the world. A simple way to fix this is to make the world wrap around, so that the left edge is connected to the right edge, and the top edge is connected to the bottom edge. This will get us perpetual water flow. It’s interesting to see how the water stabilizes over time.