METHOD FOR GENERATING CURVED-SURFACE MODEL BY REVERSIBLE ROUNDING-OFF OPERATION, METHOD FOR GENERATING LATTICE POLYGON MODEL FROM THE MODEL, RECORDING MEDIUM FOR EXECUTING THESE METHODS, AND METHOD FOR TRANSMITTING/DISPLAYING CURVED-SURFACE MODEL

摘要

PROBLEM TO BE SOLVED: To provide completely reversible rounding-off operation which can generate a stricter curved-surface model. SOLUTION: The apex P0 of a curved-surface model corresponding to each apex G of a lattice polygon model is calculated. The coordinate values of the new apexes P0 are calculated by performing linear transformation on the coordinate values of the original apex group. Then the curved edge lines of the curved-surface model corresponding to the ridge lines B of the polygon model are decided. The curved ridge lines are expressed by cubic Bezier curves. In addition, a model surrounded by the Bezier curves is interpolated by using Gregory curved surfaces. Consequently, a curved-surface model having the same phase structure as that of the lattice polygon model is generated. In addition, the curved-surface model can also be generated similarly from a lattice model which is formed by giving arbitrary apexes and the rounded-off information on the ridge lines to the lattice polygon model.