| 题名 | 表面细节特征及其在网格变形中的应用研究 |
| 作者 | 吴金钟 |
| 学位类别 | 博士 |
| 答辩日期 | 2008-05-30 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 中国科学院软件研究所 |
| 导师 | 吴恩华 |
| 关键词 | 三维模型处理 微分属性 平均曲率算子 重网格化 细节克隆 网格变形 LOD技术 外存地表绘制 多分辨率表示 |
| 其他题名 | Surface detail representation and applications in mesh deformation |
| 学位专业 | 计算机应用技术 |
| 中文摘要 | 网格变形技术是数字几何处理研究的核心技术之一，其应用方面主要包括三维数字媒体、影视娱乐、文化教育、网络休闲等。网格变形主要是研究三维虚拟物体的表面编辑、姿态变化、动画序列控制方面的技术，对象包括模型表面及模型包围的三维空间。采用的技术主要有细节表示、变形驱动、数学模型求解等。本文在前人网格变形技术的基础上，分析比较了各种技术的优缺点，指出当前网格变形技术中的研究热点，并提出细节保持、变形驱动两个方面的技术改进。本文的主要内容和技术创新点表现为以下四个方面的工作： 1. 探讨了三维模型的细节表示方法，提出了基于曲率法向算子矢量场的细节特征保持的变形方案。曲率在微分几何上有其明确的数学意义，是曲面内在的几何属性。我们通过对模型表面Dirichlet能量函数进行分析，发现了平均曲率与Dirichlet的内在关联，即平均曲率是Dirichlet能量意义下的局部细节度量。同时提出曲率参数定义，得到了线性旋转不变的曲率细节表示方法。并考察了曲率方法在网格重建、姿态编辑、细节克隆、重网格化中的应用，验证了其对模型局部特征的保持效果。 2. 针对传统关节动画不能对细节进行保持的缺点，提出了改进的细节保持关节变形。借鉴[Igarashi 2005]中以三角形边矢量为特征保持的思想，引入模型边矢量及曲率细节作为变形中保持的细节特征，改进了传统算法。 3. 提出了基于样条的三维网格编辑方法。据我们所知，应用样条方法到三角网格编辑中的研究很少，主要是由于这两种方法对模型的表达方式有很大不同，一个是采用连续的样条曲面参数化描述，一个是采用离散的三角网格。本文采用样条曲面作为控制曲面在变形中对三角网格进行驱动，同时保持三角网格顶点在样条上对应点的局部坐标不变，并采用Laplacian算子方法保持细节。基于样条的方法操作简单方便，是网格编辑很有发展的方向之一。 4. 提出了大规模外存地表模型的实时绘制技术，分别在分块多分辨率地表数据存储、分块LOD绘制、多线程I/O调度三个方面对原内存算法[Lindstrom 2002]进行改进。在不牺牲视觉效果的情况下，加快了绘制速度，达到了实时效果。 |
| 英文摘要 | Mesh deformation is one of the core technologies of digital geometry processing, and the investigation to mesh deformation is closely related to various applications such as 3D digital media, CG movies, culture and education, internet games. Mesh deformation is the technology of the study performed on 3D mesh surface and the space it embedded in, as well as the tools of surface editing, shape deformation and animation control. Three main topics for the investigation in this regard are mesh detail representation, deformation drive method, and math model solution. In this thesis, we first study the techniques proposed in the recent years on mesh deformation, and analyse the advantages and disadvantages among them. And then we present our work in detail representation and deformation control method. Our main contributions are included in the four works: 1. We propose a detail feature representation scheme based on curvature normal operator vector field. Curvature has strong mathematics background in differential geometry, and it is an intrinsic property of a smooth surface. After an analysis to Dirichlet energy function of a triangular mesh, we find out that curvature is the detail representation under Dirichlet function. Then we propose the concept of curvature coordinates, a linear rotation invariant of 3D meshes. We implement curvature detail representation on mesh reconstruction, shape editing, detail clong, and remeshing. The result proves the validity of curvature detail representation. 2. We propose an improvement to traditional skinning animation. The traditional skinning method has a drawback in lack of support to detail preservation. We propose an invariant to overcome this drawback, and use curvature vector and mesh surface edge vectors as the detail for preservation in deformation. 3. We propose a Spline based 3D triangular mesh editing method. As we know that Spline is the object representation mainly used in CAD modeling and character animation, and it is not easy to uses Spline methods on 3D meshes. In this thesis, we use Spline as the guiding control shape of a triangular mesh. The triangular mesh is attached to this Spline surface using its local coordinates system. While deformation, the local coordinates of mesh vertex keep no change and a reconstruction is needed to get the deformed mesh. We use Laplacian operator to smooth the mesh when necessary. 4. We propose a real time rendering scheme to out-of-core terrain models. In this regard, our main contribution is in the design of multi-block structure of terrain data, LOD rendering and multi-thread I/O paging. Within the threshold user specified, our terrain rendering technique achieves real time. |
| 公开日期 | 2011-03-17 |
| 内容类型 | 学位论文 |
| 源URL | [http://124.16.136.157/handle/311060/6284]  |
| 专题 | 软件研究所_计算机科学国家重点实验室 _学位论文 |
| 推荐引用方式 GB/T 7714 | 吴金钟. 表面细节特征及其在网格变形中的应用研究[D]. 中国科学院软件研究所. 中国科学院研究生院. 2008. |
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