1. Crossing IRL 2010, French National Center for Scientific Research (CNRS), Adelaide 5005, Australia
2. UMR CNRS 6285, Lab-STICC—Laboratoire des Sciences et Techniques de l’Information de la Communication et de la Connaissance, 29238 Brest, France
3. Department of Computer Science, IMT Atlantique, 29238 Brest, France
4. Australian Research Centre for Interactive and Virtual Environments, University of South Australia, Adelaide 5095, Australia