网格模型在3D建模系统以及计算机图形学中有着广泛的应用。近年来，随着三维扫描技术的发展，由逆向建模生成网格模型成为网格数据的一个重要来源。由于扫描仪本身的缺陷以及网格生成算法的限制，生成的网格模型往往会存在网格孔洞，给模型的后续应用带来很大的不便。因此，在得到网格之后需要对网格中的孔洞进行修复。 本文提出一种基于分割的网格孔洞修复算法。在补洞之前，先对孔洞做分割预处理，利用网格特征曲线将复杂的孔洞分割为若干边界相对规整的网格子洞。如果没有特征线，则使用直线段或者用户自定义的分割曲线代替特征曲线。分割之后，使用改进的AFM算法依次对每一个子洞进行修复，得到补丁网格，然后对补丁网格进行几何调整，确定其最终的拓扑结构和几何形状。本文提供了两种不同的补丁网格几何调整的方法，分别是利用泊松方程进行调整以及利用重网格化的手段进行调整，利用泊松方程调整能够使网格在孔洞边界处更加光顺，利用重网格化的调整方法得到的补丁网格具有更好的网格质量。 为了满足网格孔洞修复算法的应用需求，本文对TiGems7.0网格处理模块修改和扩展。首先对TiGems7.0网格处理模块中基础数据结构进行了扩展，使之能够支持任意多边形网格，修改了网格数据管理模块，消除了冗余的数据管理功能；其次，完善了网格处理模块对多种网格文件的支持，改进了原有的针对WRL、3DS等格式解析中的不足，增加了对DAE、X、X3D等格式的支持，使得TiGems7.0能够更方便的获取不同网格文件中的模型并进行补洞处理或者其他相关处理。最后完善了TiGems7.0中网格拾取功能。
Meshes are widely used to represent objects in Computer Graphics and Computer Aided Design. In recent years, with the development of laser scanning technology, reconstructing from 3D scanning data has become an important source of mesh. However, the limitations of the scanning technology and the reconstruction algorithm always result in some holes in the generated mesh, which has negative influence on the following application such as remeshing, mesh simplification, surface reconstruction and so on. So it is important to fill the holes after the meshes are generated. This thesis presents a hole-filling algorithm based on segmentation. After finding out the boundary of the holes, feature lines which pass through the hole are identified, so the complex hole will be divided into several simple sub-holes with simpler boundary. If there are no feature lines, straight lines are used to directly connect the split points or curves constructed by user selected points are used instead. Then each sub-hole will be filled by the Improved Advancing Front Mesh technique to obtain the corresponding hole patch. Furthermore, two different shape adjustment methods are provided. The first one is based on Poisons Equation which can make mesh around the boundary much more smoothly and the second one is based on remeshing that can improve mesh quality of the patch. To satisfy the application requirements of mesh hole-filling, this thesis modifies and extends TiGems7.0 mesh process module. Firstly, the data structure of the mesh is extended so that it can support any arbitrary polygon meshes. Then this thesis improves the support for multiple mesh file format, fixes the deficiency in parsing process of original WRL, 3DS etc and add the support for DAE, X, X3D etc file format, so that TiGems7.0 could assess models in different types of mesh files easier and fill holes or do related operation. At last the mesh selection features are improved.
