Please see this post: Simplicial Developmental System.
As part of my PhD I developed software for procedurally generating complex organic 3D forms. This software, the Simplicial Developmental System (SDS), simulates biological and physical processes in order to grow a 3D structure in a virtual environment. The user of the software specifies the initial conditions, parameters of the processes, and the environmental configuration and then starts the simulation.
I've made all my code publicly available, as is. Please note the licenses that are in the various folders and pay attention to the licenses of the included dependencies.
Please note that this code is for a prototype, it probably won't work any more but may be of some use to someone out there.
Follow me on twitter at @eigenbom to catch up with my latest adventures in procedural generation.