Research And Implement Of NURBS Free-form Surface Reconstruction Based On Scattered Point Cloud

Surface reconstruction is one of the core technologies in reverse engineering, and research in this technology field has great significance for improving and enhancing the technology level of reverse engineering. Among these researches, the scheme of free-form surface reconstruction based on NURBS has become a hotspot because of good smoothness, editing capability and same representation of product models with CAD / CAM system .On the basis of summing up research results at home and abroad, this paper studies and realizes the technology of free-form surface reconstruction from scattered point cloud based on NURBS. The main research contents and results are summarized as follows:1. Designs an interpolation algorithm to fitting NURBS surface which follows the process of "point-line-surface", and researches the key technologies. Including the algorithm of filtering and simplifying data points, the method to determine knot vectors by modifying the chord length parameterization, the method to compute control points and the algorithm of uniforming knot vectors based on binary interpolation.2. Designs an iterative search algorithm for NURBS surface accuracy assessment based on regional division. The algorithm avoids blind search and divergent computing, and also ensures good accuracy. It can quickly calculate the shortest distance between points and NURBS surface.3. In order to solve the continuous blending problem in the process of several free-form surface reconstruction, this paper derives the condition of G 0, G 1 and G 2 continuity among bicubic NURBS surfaces, then designs G 0, G 1 and G 2 continuous blending algorithms owing to which smooth blending is finished.All of the algorithms on NURBS surface reconstruction mentioned above have been implemented in a prototypical system. Test results verify the correctness and effectiveness of the algorithms in this paper.