1. Department of Computer Sciences, Center for Computational Visualization, Institute for Computational Engineering and Sciences201 East 24th Street, ACES 2.324, Austin, TX 78712-0027, USA
2. Department of Studies on Structures, Modelling & Simulation Lab, Università Roma TreVia Corrado Segre, 6 00146 Roma, Italy
3. Department of Informatics and Automation, Geometric Computation Lab, Università Roma TreVia della Vasca Navale, 79 00146 Roma, Italy