While being so evolutionary in the world of automobiles, car designs have been improved from manual to automatic to smart and now virtual. Theo Leggett has been talking to Stephen Remondi who is the chief executive of Exa Corporation, to see how 3D simulations are being used by designers to refine their work in the virtual world before a single car panel has been built in the real one. In the gone days, cars were built almost by a process of error and trail. Nowadays, much of this work is done by computers. You built a prototype, then tested it to find out what worked and what didn't.