Semiglobal deformation and correction of free-form surfaces using a mechanical alternative

Free-form surfaces deformation is difficult since more than one control point must be moved to achieve satisfying results. Simultaneous movement of control vertices provides semiglobal deformation. The method uses an analogy between the control polyhedron of a surface and the mechanical equilibrium of a bar network. Changes of mechanical parameters produce real-time shape modifications. A toolkit of basic deformation functions achieve surface inflation, tweaking and shrinking. Each equilibrium position of the network is the solution of a linear system of equations. The surface can be deformed on a local, semiglobal or global basis. Higher-level interactive functions suppress undesired bumps or wrinkles and provide real-time surface adjustment and precise control of curvature distribution.