By a process of Diffusion-Limited Aggregation, particles — moving either randomly or driven by some external input such as some audio — aggregate to some substrate when they hit it. This physical process can be observed in many different places in nature, and produces quite mesmerizing structures.

I first learnt about this system on Softology’s blog, and found his 3D structures generated with DLA very interesting. So I decided to give it a go. This project was the perfect candidate to try playing with Subsurface Scattering. Getting some good-looking SSS in real-time is quite difficult, so I was happy to investigate in some solutions in that regard. Using a voxel density field to store the aggregate of the DLA makes it possible to use raymarching for the rendering, which opens the way for some different lighting techniques usually not available with the traditional rendering pipeline. I am quite happy with the quality of the results and I will definitely be using this technique more often in my renderings.

I would also like to thanks Vincent Houzé for putting some important resources online for free, I used his project as a starting point for my raymarching renderer.

Here is a video of myself beatboxing over this system. The audio drives the particles aggregating, different emission spots are triggered by different frequency ranges: