【作者】 李立新；

【导师】 谭建荣；

【作者基本信息】 浙江大学 ， 机械设计与理论， 2001， 博士

【摘要】 曲面重建技术在曲面测量造型与可视化等领域有着广泛的应用背景。作为最具普遍性的曲面重建问题，散乱点集曲面重建无论在理论上还是在实用上都有重要意义。 第一章绪论对解决曲面重建问题的几种相关技术，即三角剖分与拓扑重建技术、网格优化与简化技术、曲面造型与几何重建技术等作了简要回顾。结合曲面重建问题的研究现状，围绕拓扑重建与几何重建这两个关键技术，提出了本文付诸研究并取得进展的若干问题。 第二章将曲面三角剖分与曲面集的邻域特征相联系，讨论了在曲面集上测取一个散乱点集来刻划曲面集的二维流形特征时应该考虑的三个因素：即单张曲面的局部弯曲程度、单张曲面的整体弯曲程度以及不同曲面间的邻近程度。在此基础上，给出了平展的曲面三角剖分、局部分离样本以及全局分离样本的定义。 第三章研究了散乱点集的邻域结构及其经典算法。提出并论证了两种计算散乱点集Delaunay三角剖分的方法，即平面点集Delaunay三角剖分的局部构造算法和空间点集Delaunay三角剖分的健壮算法。提出了二维流形可辨性问题，并指出了散乱点集的邻域结构与二维流形可辨性之间的关系。 第四章提出一种基于二维流形可辨性的散乱数据曲面拓扑重建算法。该算法适用于包括单侧曲面在内的光滑且不自交的任意拓扑曲面集，且重建结果是相对优化的曲面三角形剖分。当所给点集是闭曲面集的局部分离样本或已知采样空洞半径的全局分离样本时，本算法将给出正确的重建结果；当所给点集在某些样点处不满足分离条件时，算法将给出相应的空洞以供参考。本章还给出了从拓扑相容的三角形集合中提取拓扑信息的算法和公式。 第五章针对任意拓扑曲面的几何重建问题，提出了两种新的C-T分割算法：一种采用了三角域上的B-B曲面，另一种采用了矩形域上的Bézier曲面。第一种算法的特点是重建结果不依赖于顶点的处理顺序，不需要进行控制顶点的初估及修正，可使各控制顶点的计算一次完成。第二种算法的创新之处在于它首次在该问题上采用了矩形域上的Bézier曲面，因而可被大多数CAD/CAM软件所直接采用。由于两种算法都是完全局部的，且对多余的自由度进行了合理的分配，因此具有较高的效率，并可构造相对光顺的插值曲面。 第六章讨论了Floater关于四边拓扑曲面的双三次B样条几何重建方法在圆一 摘 要 浙江大学博士学位论文 一 盘拓扑曲面上的应用，并将其推广到平环与Mbbius带上。指出并证明了Floater 线性方程组的一个重要性质，并在此基础上提出了该方程组的一种专用解法。 该解法在时间和空间上都获得了线性复杂度，其数值稳定性与标度化全选主元 素法相同，从而显著提高了Floater方法的效率。 第七章以皮鞋CAD软件的开发为背景，着重介绍了其中曲面测量造型系统 的主要功能、实现方法与应用实例。同时给出了本文算法在有限元网格自动剖 分中的应用。 第八章对本文的研究工作进行了总结，并对曲面重建领域的发展前景进行 了展望。更多还原

【Abstract】 The technique of surface reconstruction has extensive use in surface measuring modification and visualization and such fields. The technique of surface reconstruction from scattered points, for its universality, is very important both theoretically and practically.In chapter 1, a brief review is made about several relative techniques, e.g., triangulation vs. topologic reconstruction, mesh optimization or simplification, and surface modification vs. geometric reconstruction. Based on the present state of investigation, several problems are put forward about topologic reconstruction and geometric reconstruction which have been studied carefully in this dissertation .In chapter 2, surface triangulation and local feature of a surface set are considered together. Three factors are discussed which should be taken into account when sampling points from a surface set to describe its 2d manifold feature. These three factors are local bending degree of a single piece of surface, overall bending degree of a single piece of surface and vicinity degree between different surfaces. The definitions of flat surface triangulation, local separate sample and overall separate sample are given based on this discussion.In chapter 3, the local structure of a scattered point set and its classical algorithms are investigated. Two algorithms for Delaunay triangulation from scattered points are suggested, one of which is from points in plane and the other from points in space. The problem of recognizability of 2d manifold is promoted and the relationship is pointed out between such recognizability and the local structure of a scattered point set.In chapter 4, based .on the recognizability of 2d manifold, an algorithm is presented for topologic reconstruction from scattered points. The algorithm is applicable to nonself-intersectant smooth surface set of any topology, including nonorientable surfaces, and its result is optimal surface triangulation in a way. When the given point set is a local separate sample of a closed surface set or an overall separate sample with known radius of sampling hole, the algorithm will reconstruct a correct result; when the separate condition is not satisfied at some points, the algorithm will give result with corresponding holes. The algorithms and formulas are promoted for extracting the topological information from a set of triangles which are topologically compatible.In chapter 5, two new C-T algorithms are proposed for geometric reconstruction, one of which adopts B-B patches on triangles and the other Bezier patches onrectangles. The first algorithm gives unique result unaffected by the handling order of points concerned, and it calculates the control vertexes at once without estimation and correction. The originality innovation of the second algorithm is that it adopts Bezier patches on rectangles for the first time in this problem, hence can be directly adopted by most CAD/CAM software. Because the two algorithms are confined to local area, and assign redundant degrees of freedom reasonably, they are highly efficient and can give relatively smooth fitting surface.In chapter 6, the usage of Floater’s algorithm on a disk is discussed which is for geometric reconstruction of surface with four edges using double cubic B-spline surface, and the algorithm is generalized to a cylinder and a Mobius. An important property of the Floter linear system is pointed out and proved, and based on this, a special solution method for it is proposed. This solution method has a linear complexity both in time and space, and its numerical stability is similar to that of overall selected host element with normalization, hence remarkably improves the efficiency of Floater’s algorithm.In chapter 7, under the background of Shoe CAD software development, the surface measuring modification system therein is introduced with its main functions, implementation methods and application samples. At the same time, the algorithm in this dissertation is used to generate finite element mesh automatically.In cha更多还原