The purpose of this paper is to describe features for simulation of crack propagation being implemented in FRANSYS, a fracture simulation system currently under development at the Program of Computer Graphics at Cornell University. Routines for the computation of stress intensity factors for three-dimensional cracks in arbitrary bodies are described. An example application is presented and compared with an analytical solution. Features to update the model to accommodate additional surfaces required by crack propagation are also described. Preliminary results for three-dimensional crack propagation are presented in an example application.