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### Interactivity : expressing Expressing  3D information Information  in 2D The web as a publishing platform allows authors to include graphics that move. While stereoscopic 3D viewing on 2D surfaces is possible (and improving), cognition research shows that presently the best way for humans to understand 3D geometry on a 2D screen is to be able to manipulate 3D perspective views dynamically, so as to simulate views created by moving around in real space.