Virtual worlds are simulated environments with internal rules inspired at least in part by real physics laws. This type of environment has been fruitful for ALife research, for it allows quick implementation of reality-inspired behavior that can be visualized as computer animations [123,124,114,101,81].
The surreal beauty of some artificial agents in virtual worlds has had a profound
impact in the field, most famously Karl Sims' virtual creatures, made
of rectangular prisms, evolved life-like behaviors and motion under a careful
physical simulation (fig. 1.2).