基于分割点云的NURBS曲面三维重构方法研究

发布时间：2018-01-17 19:08

本文关键词：基于分割点云的NURBS曲面三维重构方法研究　出处：《北京建筑大学》2013年硕士论文　论文类型：学位论文

【摘要】：三维激光扫描作为一种高速收集对象精细、稠密的表面数据的扫描技术，近年来在工业设计、现代大型异构工程施工、文物保护等领域得到了广泛的使用。以上领域都需要对物体的原始点云数据进行三维构建，在构建结果的基础上分析和利用。例如：在大型异构工程构件的施工放样中，需要对构件重建，在计算机中模拟其拼接效果，并根据需要实时对其姿态等进行调整；在文物保护与文化遗产领域，需要重构扫描物体的外形特征，以便现实中重建、分析、仿真等应用；在工业设计中，一些物体细节处的重要特征很难获取，但通过重建物体表面可以轻易的将手工雕刻模型输入到CAD系统中；在逆向工程中，往往有大量的传统零部件必须先测量重建出其表面形状信息进而改进修正设计出的新品；另外，重建也可以作为检查站站之间数据遗漏或空洞的重要手段。基于点云的三维重建在整个数字化过程中起着关键的作用，重构模型的精度与速度直接影响后续工作的开展。因此寻找一种高效灵活的建模方法是十分必要的。本文综合阐述了基于NURBS理论进行曲面重构的原理、研究现状和技术方案，并分析了该方向的总体发展和现有解决方案的不足之处，得出基于切片技术构建分割点云的NURBS曲面的方法。论文的主要研究内容包括下面四部分： 1．对已分割的散乱点云数据采用点云切片技术，提取用于构建NURBS曲线曲面的型值点序列，并研究了点云切片的参数设置规则。这些参数包括切片的层数，切片的行进路线，切片之间的距离以及切片本身的厚薄程度，并深入研究了对于不同特征的点云的切片行进路线的判定方法。 2．在构建NURBS之前，对切片数据进行预处理，采用一种逐点斜率求差法进行数据压缩，，用最少的数据点保证曲面的形状，根据处理后得到的新数据点求取控制点，也可以达到用存储量小的控制点重构符合精度要求的NURBS曲面。 3．在计算NURBS构建所需要的控制点时，本文选用三次B样条曲线，采用重节点技术进行曲线曲面插值，其中的附加条件采用以首末型值点为基础，通过方程解算控制点，是一种不同于边界附加条件的简单控制顶点解算方法。 4．对构建的NURBS曲面采用基于网格划分的迭代搜索法进行精度分析。以点云到曲面的相关距离数值为依据进行评定。应用这种方法，可以减小搜索范围，提高搜索的效率。根据本文研究内容的具体含义和选择的技术方案，即以分割点云数据为基础，以构建双三次NURBS曲面为目的，采用快捷、简单、精确的方法进行三维重构，并对构建的曲面进行精度分析。本文使用C++高级编程语言，结合OpenGL开发实验系统，选用项目中的相关数据来验证算法的可实用性，总结本文研究的技术路线，以及其实用性与精确性等。
[Abstract]:3D laser scanning as a high speed collection of fine, dense surface data scanning technology, in recent years in industrial design, modern large-scale heterogeneous engineering construction. Cultural relic conservation and other fields have been widely used. The above fields need to construct the original point cloud data. On the basis of the results of the construction analysis and utilization, for example, in the construction of large heterogeneous engineering components, it is necessary to rebuild the components, and simulate the splicing effect in the computer. And according to the need of real-time adjustment of its attitude; In the field of cultural relics protection and cultural heritage, it is necessary to reconstruct the external features of scanned objects for the purpose of reconstruction, analysis, simulation and other applications in reality. In industrial design, it is difficult to obtain the important features of some object details, but the manual carving model can be easily input into the CAD system by reconstructing the surface of the object. In reverse engineering, a large number of traditional parts must first measure and reconstruct their surface shape information to improve the design of new products. In addition, reconstruction can also be used as an important means of missing data or voids between checkpoints. 3D reconstruction based on point cloud plays a key role in the whole digitization process. The precision and speed of the reconstruction model directly affect the development of subsequent work. Therefore, it is necessary to find an efficient and flexible modeling method. This paper comprehensively describes the principle of surface reconstruction based on NURBS theory. The current situation and technical scheme are studied, and the overall development of this direction and the shortcomings of the existing solutions are analyzed. The method of constructing NURBS surface based on slicing technology is obtained. The main contents of this paper include the following four parts: 1. Point cloud slicing technique is used to extract the sequence of value points used to construct NURBS curve and surface. These parameters include the number of layers, the route of the slice, the distance between slices and the thickness and thickness of the slice itself. The method of determining the path of slicing of point clouds with different characteristics is also studied in depth. 2. Before constructing NURBS, the slice data is preprocessed, a method of point by point slope difference is used to compress the data, and the shape of the surface is guaranteed with the least number of data points. According to the new data points obtained after processing, the control points can be obtained, and the NURBS surface can be reconstructed by using the control points with small storage capacity to meet the precision requirements. 3. In the calculation of the control points needed by NURBS, the cubic B-spline curve is selected, and the curve and surface interpolation is carried out by using the heavy node technique, in which the additional conditions are based on the first and last value points. The solution of control points by equation is a simple method for solving control vertices, which is different from the boundary additional conditions. 4. The precision of the constructed NURBS surface is analyzed by the iterative search method based on mesh division. Based on the relative distance between the point cloud and the surface, the method is applied. Can reduce the search range, improve the efficiency of the search. According to the specific meaning of the research content and the choice of the technical scheme, that is, based on the segmentation of point cloud data, to build a bicubic NURBS surface for the purpose of using fast and simple. In this paper, we use C high-level programming language, combined with OpenGL to develop the experimental system. The relevant data in the project are selected to verify the practicability of the algorithm, and the technical route, practicability and accuracy of this paper are summarized.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：P225.2

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