Subdivision surfaces in MPEG-4

SS (subdivision surfaces) are a powerful modelling paradigm for truly hierarchical (instead of merely progressive) 3D surface (as opposed to mesh) coding. Two SS-based tools of the MPEG-4 animation framework extension allow us to derive a piecewise smooth surface from an initial control mesh: if the subdivision process is run in its predefined form, the initial mesh is simply smoothed; if 3D details are added to the positions of the new vertices appearing after each subdivision step, a particular target surface may be approximated with an increasing accuracy. In both cases, multiresolution editing/animation is possible.