Geometric Modeling Technology In Reverse Flexible Surface Reconstruction Technology Research

As an important technology of absorbing advanced technique and shorting again-design time, reverse-engineering in geometric modeling has been a hot spot in manufacturing field of computer. Free-surface reconstruction is one of nuclear problems in research on reverse-engineering of geometric modeling. The quality of surface-reconstruction of geometric modeling will determine the availability of reverse-engineering system. How to improve the quality and speed of surface-reconstruction is a main subject to discuss in this paper.The paper explored some theories and resolutions about geometric modeling.This paper introduces theoretical basis of surface reconstruction and geometric modeling, emphasizes the basic principle and algorithms of free curves and surfaces, and defines the data structure of practical system.Aiming for the application of surface reconstruction technology of3D scanned data points in practical system, a flexible surface-reconstruction method based on approximation is proposed, which overcomes the shortcoming that traditional surface-reconstruction methods can not deal with non-uniform scanned data, or the shape of result surface is distorted, or the procedure of computation is unstable, this method has been verified in practical system.The surface skinning in geometrical modeling is a procedure of reconstructing surface based on a series of section curves, these curves maybe have different degree, different knot vectors, maybe be rational or nonrational, so some unexpected shapes can be produced. In order to keep surface smooth and flexible, compatibility is necessary to deal with, this procedure will inevitably produce many problems, such as largely increasing data amount which is necessary to deal with and the number of control points, low efficiency, etc. surface skinning sometimes can generate the variation of surface shape and some problem of parameterization, so an improved method of surface skinning is proposed. This method use flexible selection of knot vectors to make the parameterization of result surface not be effected by different distribution of each section line and it can reduce the number of control points effectively.By applying3D graphic standard and OpenGL library, above algorithms on VC++platform have been accomplished in practical system. The software system has the functions of man-machine conversation, editing, lighting, rendering, etc. It can produce excellent effect of geometric modeling.