This is a grasshopper add-on for agent-based modelling based on physarum polycephalum. It is a stigmergy algorithms similar to ant colony algorithm.
Physarum polycephalum, literally the "many-headed slime", is a slime mold that inhabits shady, cool, moist areas, such as decaying leaves and logs. P. polycephalum is one of the easiest eukaryotic microbes to grow in culture, and has been used as a model organism for many studies involving amoeboid movement and cell motility. For example, a team of Japanese and Hungarian researchers have shown P. polycephalum can solve the Shortest path problem. When grown in a maze with oatmeal at two spots, P. polycephalum retracts from everywhere in the maze, except the shortest route connecting the two food sources.

Based on Prof. Jones's Processing program, I put it to 3D and wrote this pulgin for Rhino/Grasshopper. I add some new features to gain more artistic expression. In addition, I am working on it so that physarum can run on a mesh.
This plugin is part of my design studio at School of Architecture, Tsinghua University. Although ths studio is over, I find there a plenty of bugs in the program. So I'm still developing it. You can come back and check it later.
Please feel free to contact me.
Ma Yidong
MArch at SOA, Tsinghua University, Beijing.