Constrained diffusion-limited aggregation in 3 dimensions

Diffusion-limited aggregation (DLA) has usually been studied in 2 dimensions as a model of fractal growth processes such as river networks, plant branching, frost on glass, electro-deposition, lightning, mineral deposits, and coral. Here, the basic principles are extended into 3 dimensions and used to create, among other things, believable models of root systems. An additional innovation is a means of constraining the growth of the 3D DLA by a surface or containing it within a vessel.