关键词: 计算机辅助设计, 非均匀有理B样条, 曲面造型, 　型值点

Abstract: A new algorithm of Non Uniform Rational B-Spline (NURBS) extension was proposed. A sequence of characteristic-points was created based on the analysis of the NURBS curves to be extended firstly. By inserting the extending points into the sequence of characteristic-points, a new extending curve was interpolated. Finally, an optimization procedure was applied on the new extending curve to have a very simple data structure to proceed to next extending procedure more easily. Particularly, a tolerance value was presented to adjust the accuracy of calculating procedure, so that the best balance between speed and accuracy of the calculating was achieved. Moreover, some forms of the NURBS extension were discussed and the methods of extending points calculating were presented, and results of the algorithm were also provided.

Key words: computer aided design, non uniform rational b-spline, surface modeling, characteristic-point