Audrey St. John

Java applet demos

Demos that quickly prototype approaches to gain intuition and provide tools for demonstration.
Pebble Games for Sparse Graphs
Pebble games are based on an elegant and simple algorithm introduced by Jacobs and Hendrickson in 1997 for 2D bar-and-joint rigidity. We generalized the 2D game to a family of pebble game algorithms, which characterize a counting condition called sparsity in graphs.

2D Motion Simulation for Bar-and-Joint Frameworks
By adapting the ragdoll physics technique, introduced by the game industry, we can simulate motion of bar-and-joint frameworks in the plane. Note that, because this simulation is not based on Laman's condition for generic rigidity, it is able to handle frameworks in so-called "special position."