Generation of free-form surface models by understanding geometric and topological constraints on rough sketches

The geometric modeler developed enables a style designer to define free-form curves and surfaces by rough sketches directly drawn on a display. For the generation of curves, methods to automatically analyze symmetric and corresponding geometric pairs on the sketch and to calculate 3D rational Bezier curves from them are proposed. Also, methods to generate free-form surfaces over a nonrectangular area and to modify the internal shape of the surface by 2-D curves are discussed