Chain-based polyline tessellation algorithm for cartographic rendering

ABSTRACT

Although the extrusion of 1D polylines into a 2D polygon and the tessellation of the polygon into primitives has been performed in the field of computer graphics, the efficient, robust, and high-quality tessellation of thick polylines that supports various cartographic styles for polyline rendering remains a practical challenge. We examined and compared existing vertex-, segment-, and polygon-based algorithms, and present a chain-based tessellation algorithm for cartographic rendering: points in the polyline are classified into abrupt and smooth points according to their point spacing, angle and thickness. The polylines are then divided into abrupt and smooth chains by clustering points that are adjacent and of the same type. An optimal algorithm is also presented to continuously tessellate the smooth chains into minimum geometric primitives and efficiently tessellate the abrupt chains into geometric primitives. We implemented the proposed algorithm and present the results of robustness, efficiency, quality, and cartographic styling tests conducted on real-world polylines. The results indicate that this approach has substantial advantages when considering all four requirements (robustness, efficiency, quality, and the support for various cartographic styles).     

基于C#的地理信息控件研究

在小型的地理信息系统中,采用自制的地理信息控件,有针对性强、体积小、拥有自主产权等优点。本文将基于几何模型、地图的渲染和数据接口3个方面分析并介绍基于C#制作地理信息控件的技术。     

Geometrically valid pixel reprojection methods for novel view synthesis

Conventional methods for scene visualization involve 3-D model reconstruction and direct rendering of the model. More recently, however, there has been an increasing interest in an alternative means for novel view synthesis, namely image-based rendering. It refers to a collection of techniques for creating new views directly from a set of input images; these images act as the scene `model'. This paper describes in detail a particular subset of image-based rendering techniques, which we refer to as geometrically valid pixel reprojection techniques. These techniques are based on established bilinear and trilinear image constraints in the forms of the fundamental matrix and trilinear tensor, respectively. We also describe an image-based rendering technique that uses as input a collection of cylindrical panoramic images.     

A virtual globe-based vector data model: quaternary quadrangle vector tile model

This study proposes a virtual globe-based vector data model named the quaternary quadrangle vector tile model (QQVTM) in order to better manage, visualize, and analyze massive amounts of global multi-scale vector data. The model integrates the quaternary quadrangle mesh (a discrete global grid system) and global image, terrain, and vector data. A QQVTM-based organization method is presented to organize global multi-scale vector data, including linear and polygonal vector data. In addition, tile-based reconstruction algorithms are designed to search and stitch the vector fragments scattered in tiles to reconstruct and store the entire vector geometries to support vector query and 3D analysis of global datasets. These organized vector data are in turn visualized and queried using a geometry-based approach. Our experimental results demonstrate that the QQVTM can satisfy the requirements for global vector data organization, visualization, and querying. Moreover, the QQVTM performs better than unorganized 2D vectors regarding rendering efficiency and better than the latitude–longitude-based approach regarding data redundancy.     

基于CUDA的三维重建过程实时可视化方法

在某些用于在线控制的CT系统中,经常有必要在扫描过程中检查中间结果从而排除故障。然而实时的重建与体绘制对系统计算能力的要求非常高,难以实现。本文针对锥束CT提出了一整套实时重建可视化方法,并在最新的图形处理器Tesla C 1060上实现。与传统的工作方式不同,这种方法在扫描得到每一张投影后,实时显示重建过程的中间结果。通过这种方法,可以很清楚地观察到投影数据逐步合成三维重建结果的过程,也可以预先看到探测器的缺陷对重建结果造成的破坏。同时,这种方法也是实现4D CT可视化的一种有效途径。     

基于OSG的MCSEM施工实时监测方法

三维实时MCSEM监测系统强调的是监测的实时性,以三维可视化方式实时显示施工过程,有利于直观地监测和判断工作过程是否存在异常。根据MCSEM作业方式与流程,研究了在OSG三维渲染引擎的开发环境下,三维场景实时动态更新方法,包括三维模型实时更新、海底地形、轨迹线等要素绘制和相机实时跟踪;研究了三维场景数据组织结构与渲染状态机制,优化场景渲染,提高场景的响应速率,尽量保证三维显示的实时性、流畅性;开发了三维实时MCSEM监测系统进行实例验证,经过大量数据多次测试,系统运行稳定、响应及时,三维显示效果良好,较好地满足了实时监测的要求。     

高性能GIS动态目标渲染引擎的设计与实现

针对海量动态目标渲染效率较慢的问题,本文研究并设计了基于混合加速的高性能GIS动态目标渲染引擎,并利用SuperMap的组件GIS研发了动态目标渲染引擎原型系统.通过比较不同类型海量空间数据的可视化实验结果表明,本文研究成果在渲染二维和三维空间海量动态目标时,满足GIS高性能可视化需求,可视化效果流畅.     

基于FLASH的湛江虚拟旅游全景漫游与导航系统

探讨了基于FLASH的湛江虚拟旅游网上导航与全景漫游系统的构建以及各项关键技术,设计并实现了基于PV3D的全景浏览器,提出了基于Flash的旅游交通导航机制,对经典的A*算法作了改进,能够在网页上快速地计算出任意两个景点之间的最短路径,从而为自架车游客提供了最短路径导航服务;开发了管理维护性后台,对全景漫游、自驾车导航和公交车导航模块提供有效的增加、修改,删除信息。实际应用表明,该系统具有很好的跨平台、免插件、高效、扩展性和维护性。     

三维地震数据的体绘制

体视化技术是三维地震数据浏览、分析和解释的有效工具。对于理解地震数据中蕴涵的结构和地层学信息，体视化比使用一组二维切片表示三维数据更自然。解释人员可以突出数据体中某些特定的区域体，以利于更好地理解它们的空间分布，也可以添加合并两个或者更多的，具有不同地震特征的体积区域。医学应用方面的一些体视化方法不能直接应用于地震数据方面．必须考虑地震数据自身特点才能使可视化成功实现。通过分析三维地震数据的特点进而得出实现三维地震数据体视化算法的基本方法，并对实际数据进行了实验。     

数字城市的三维图形构建技术

城市是一个复杂的人文与自然的复合系统,是人口、资源、环境和社会经济要素高度密集的地理综合体,数字城市是数字地球应用的一个重要方向,而数字城市的三维图形构建是数字城市建设的重要内容之一。本文从技术应用角度出发,综合多方的研究成果,简单阐述了数字城市的三维图形构建技术和基本思路。