Flow fields on necessary-disorder.tumblr.com

I like this effect. A lot.

It’s also a good demonstration how you can have a higher-order structured process driving an output. It’s obvious that there are rules that govern how the particles are moving, but it is not a direct mapping like you see in a terrain heightfield that directly uses Perlin noise.

Etienne has a tutorial for how to make this effect, if you’re interested in building on it yourself.