【作者】 龚汇丰；

【导师】 万定生；

【作者基本信息】 河海大学 ， 计算机软件与理论， 2006， 硕士

【摘要】 长期以来,地理信息系统资料的分析解释成果局限于二维静态表达方式,它给人们直接、完整、准确地理解与感受成果所反映的地表地形地貌情况造成了困难,也限制了资料的充分利用。科学计算可视化技术的发展为利用GIS资料分析解释成果、重建地表三维模型创造了条件。 本文针对当前地形三维可视化及其实时绘制技术的研究现状,在吸取三维计算机图形学、科学计算可视化、虚拟现实的先进理论和技术成果的基础上,围绕地形三维可视化及其实时绘制技术中的地形简化、层次细节、三维真实感地形生成等核心技术内容展开讨论与研究,提出了一种基于地形四叉树实时构建地形多分辨率模型的优化算法,该算法采用分块分层的思想。首先将大规模高程数据进行分块,然后对块内数据按照分辨率的大小分层存储,并给出一种与视点相依赖的对地形节点误差进行评价的方法,在网格的生成中只使用一次四叉树遍历,从而大大提高了渲染速度。 作者结合参加水利部科技创新项目“引江济太三维模拟系统”的经验体会与实践以本论文的理论研究成果为基础开发了一个三维可视化系统。系统具有数据输入与预处理,地表三维模型的计算机重构,三维模型的实时动态简化与多分辨率表示等功能。实验表明所提出的方法高效可行。更多还原

【Abstract】 For a long time past, all of the interpretation results from GIS data have been displayed or mapped by having resort to 2D and static approach. That creates difficulty for people to tell immediately and positively what the overall results means about the terrain surface. Also, the relevant information obtained could not be brought into its full play. The technique of visualization in scientific computing paves a way to rebuild 3D terrain model using the interpreted result of GIS data.This thesis focuses on the theoretical and methodological studies in the several subtopics: 3D terrain visualization and rendering, terrain simplification, LOD(Level of Detail), and multiresolution terrain representation. These studies are based on lots of advanced results of 3D computer graphics, scientific computation visualization, and virtual reality. A quadtree-based optimization algorithm for dynamically generation continuous levels of a given complex landscape in real time is developed. In this algorithm, an thought of "partitioning the terrain both spatially and resolution" is applied. It first partitions the large DEM data into some smaller sub-blocks and then stores the data in resolution order in each sub-block, the view-dependent dynamic node error evaluation method is also proposed. Rendering speed is greatly improved by using only one quadtree traversal in mesh generation.At last, based on the researched result of the above problematic situation, the three-dimensional visualization system has been established combining with experience and practice in the item of "3D-Dynamic Simulation System (derivating the water from Changjiang to Taihu Lake)". The system has these functions: Data can be received and pretreatment, three-dimensional visualization and dynamical display of terrain, three-dimensional model real-time dynamic simplification and multiresolution representation. Empirical tests show the method is robust, and fast.更多还原