三维地形可视化技术的研究

由于三维地形可视化有广阔的应用前景,近来越来越受到人们的关注。该文介绍了地形可视化涉及到的数字地形模型、三维地形的显示、地形的多分辨率模型等领域的一些概念和研究成果,重点介绍了层次细节技术在：维地形可视化中的应用。最后使用一个简单高效的节点评价函数,编程实现了基于四叉树的动态多分辨率三维地形。试验结果表明,LOD方法可以很好地满足三维地形可视化和虚拟现实应用中地形实时简化和显示的要求。     

大规模地形真实感渲染技术研究

针对快速增长的数据规模和计算机图形硬件处理能力之间的矛盾,对大规模地形真实感渲染技术进行研究。采用基于四叉树的层次细节算法渲染大规模地形,设计四叉树地形的存储结构,以视距和地形粗糙度的双重标准确定地形节点的细节程度,给出利用裙边修补裂缝的方法。实验结果表明,该技术能快速实时地完成大规模地形数据的调度和场景的真实感渲染。     

基于三角形带的地形可视化算法研究

三维地形可视化是三维视景仿真的重要组成部分.目前多数地形LOD算法以地形本身的数据结构为出发点,在绘制过程中地形网格中的三角形一般作为独立的元素在图形加速卡中渲染,在一定程度上降低了效率.对基于三角形带的地形可视化算法深入研究,首先使用交叉存取的四叉树数据结构对网格进行表示,表示方法有利于在显示过程中实时产生三角形带,通过嵌套误差判据球来确定顶点的活跃度,最后所产生的地形网格是一个三角形带,有利于加快显卡的处理速度,提高了显示效率.实验结果表明,算法是可行的.     

基于ROAM的实时动态地形可视化研究

为了获得逼真的三维漫游效果,在对ROAM算法进行研究和实验的基础上,实现基于二叉树的地形模型连续多分辨率渲染;在地形数据管理上,设计一种分块策略;综合考虑地形粗糙度和视距,提出一种合理的节点评价准则;为有效地消除地形块间的裂缝,设计一种基于邻接关系的强制剖分方法。实验结果表明,该算法在保证真实感的前提下能获得较好的帧绘制速率,实现三维地形的实时漫游。     

嵌入式地形三维可视化技术研究与实现

提出了一种基于正方形的视区裁剪方法,该方法通过地形节点的坐标来测试其可见性,实现了与视相关的地形简化。在此基础上,将等间隔取点的数字高程模型DEM和细节层次（LOD）技术用于嵌入式系统,基于OpenGL ES,在普通移动智能终端上实现了三维地形的快速建模以及动态显示。     

嵌入式三维地形可视化技术的研究与实现

介绍嵌入式系统和OpenGL ES的基本概念以及以WINCE为平台进行OpenGL ES编程的方法。对嵌入式地形可视化进行总体设计,并结合OpenGL ES图形库,以Embedded Visual C++ 4.0(EVC)为应用程序开发平台模拟三维地形显示,实现嵌入式系统上三维地形的快速建模以及动态显示,通过漫游功能、纹理映射和立方体天空盒增强地形的三维真实感。     

基于VC和OpenGL的地形三维可视化

介绍了OpenGL的基本概念及以MFC为平台进行OpenGL编程的方法，详细说明了以Visual C＋＋6．0为开发平台，用OpenGL进行地形模型的映射、三维真实感地形生成以及交互式动态显示的计算机实现过程，并用实例验证了这一方法的可行性。     

基于等高线的三维地形造型和可视化技术研究

本文介绍了等高线地图的数字化和根据数字化等高线进行三维地形造型的相关方法，最后提出了三维地形的可视化技术，从而生成真实感的三维地形。     

大规模地形实时可视化算法

提出一种实现大规模三维地形可视化的算法。该算法主要通过地形数据分块和多线程数据动态调度技术实现海量地形数据的实时动态调度,利用四叉树结构来简化地形网格,通过引入Y型基元的方法消除边界裂缝。实验结果表明,采用该方法可以实时生成大规模地形,提高地形漫游的效率与可视化效果。     

三维地形生成及其可视化处理研究

针对在三维地形处理领域中存在的地形数据获取困难,可视化处理过程复杂真实感效果不强的问题.文中提出了一种三维地形生成和可视化处理的方法,该方法采用分形算法生成虚拟地形数据,然后将其存储为地理信息系统中通用的数字高程数据格式,最后将数据导入三维建模软件Multigen Creator 3.0中,结合网格生成、三维投影和纹理映射等,进行可视化处理.仿真试验表明:该方法能快速获取有效的地形高程数据,经过处理后得到了直观的,真实感较强的三维显示效果图.该文为三维地形生成和可视化处理问题提供了一种有效的、可实现的处理方法.     

加速的QTA地形可视化算法

四叉树图集光线跟踪算法（QTA）是一种高效的平面地形可视化算法,在地形渲染相关的许多应用中（如矢量数据、谷地检测、等高线绘制等）都可以增加系统渲染速率。在QTA基础上,通过简化其中CRC算法的分支判断,引入新的屏幕误差控制策略,提出了一种新的光线投射地形可视化算法,同时对QTA中光栅化部分也进行了优化。该算法易于实现,且突破了原QTA算法只适用于平面地形的限制,算法实现了球形地形的可视化。实验结果验证了这一点,同时实验还显示,算法在不损失精度的情况下,具有更高的渲染速率。     

辣椒植株三维重构与可视化研究

为构建辣椒植株可视化模型,借助三维数字化仪获取了辣椒枝干、叶片和果实的真三维数据,结合球B样条曲线模拟了枝干的三维形态,利用NURBS曲面和T样条拼接方法建立了辣椒果实几何模型,描述节、果实的凹凸、顶端叶序等局部特征,在各器官的自动着生过程中,避免器官间的碰撞.模拟结果表明,该方法得到的模型较真实地反映了辣椒的诸多细节,具有较高的真实感,为辣椒三维形态交互设计和可视化模拟提供了技术支撑.     

3D可视化输电线路中杆塔空间挂点计算

将3D可视化技术应用于输电线路管理是当前电力信息化的发展方向.地球是一个不规则椭球体,很难计算出杆塔挂点在地球空间的坐标,因此无法真实、准确地表达线路与杆塔挂点的连接情况.为此,结合大量分析和研究,提出了一种基于Google Earth的杆塔空间挂点计算方法,并应用于所开发的输电线路管理系统中.实践表明,该方法具有计算简单、空间定位精度高、线路与挂点连接逼真等特点,能够满足现有应用的要求.     

Web-based three-dimensional geo-referenced visualization

This paper addresses several approaches to implementing web-based, three-dimensional (3-D), geo-referenced visualization. The discussion focuses on the relationship between multi-dimensional data sets and applications, as well as the thick/thin client and heavy/light server structure. Two models of data sets are addressed in this paper. One is the use of traditional 3-D data format such as 3-D Studio Max, Open Inventor 2.0, Vis5D and OBJ. The other is modelled by a web-based language such as VRML. Also, traditional languages such as C and C++, as well as web-based programming tools such as Java, Java3D and ActiveX, can be used for developing applications. The strengths and weaknesses of each approach are elaborated. Four practical solutions for using VRML and Java, Java and Java3D, VRML and ActiveX and Java wrapper classes (Java and C/C++), to develop applications are presented for web-based, real-time interactive and explorative visualization.     

An on‐line performance visualization technology

A new software technology for on‐line performance analysis and the visualization of complex parallel and distributed systems is presented. Often heterogeneous, these systems need capabilities for the flexible integration and configuration of performance analysis and visualization. Our technology is based on an object‐oriented framework for the rapid prototyping and development of distributable visual objects. The visual objects consist of two levels, a platform/device‐specific low level and an analysis‐ and visualization‐specific high level. We have developed a very high‐level markup language called VOML and a compiler for the component‐based development of high‐level visual objects. The VOML is based on a software architecture for on‐line event processing and performance visualization called EPIRA. The technology lends itself to constructing high‐level visual objects from globally distributed component definitions. Details of the technology and tools used, as well as how an example visual object can be rapidly prototyped from several reusable components, are presented. Copyright © 2003 John Wiley & Sons, Ltd.     

A real-time terrain visualization algorithm using wavelet-based compression

We propose a real-time terrain visualization algorithm combined with wavelet-based compression. Our approach updates a surface mesh model in real time by using wavelet coefficients and height data decoded from a compressed bitstream. To achieve this, a new mesh approximation method using restricted quadtree triangulation is designed on the basis of wavelet coefficients representing surface complexity. Also, a wavelet-based compression having a multiresolution structure is introduced to handle large terrain data interactively. Simulation results demonstrate that the proposed algorithm is prospective for applications in a network environment where narrow bandwidth and low computational power are usually allowed .     

基于VRML的三维地形场景生成.

详细分析了VRML的特点、动态交互的原理及其在VRML中三维地形场景的生成技术。依照VRML语法扩展了适合三维地形网络表达的VRML原型节点，从而将使三维大规模地形数据可直接进入VRML世界、高精度数学运算和实时交互漫游。     

Interactive visualization of three-dimensional magnetic fields

In order to observe the physical values (magnetic flux density and eddy current) in 3D magnetic field analysis, an interactive and highly manipulative visualization system depicting stereo images is intalled in a graphics workstation with high functional graphic processors. The system has the following characteristics:

• 1 An interactive and highly manipulative menu window with many functions: it enables visualization of complex phenomena in a 3D field through observation of various combinations of physical values from various viewpoints.
• 2 Simultaneous display of both magnetic flux density and eddy current by using the appropriate use of two colour display methods for stream lines and distribution maps of density: this function facilitates observation of the mutual relations between two physical values in a 3D field.
• 3 Animations and stereo displays: since they give extremely distinct images, observers can easily understand even highly complex 3D phenomena.

In this paper, the calculation method of density vectors, their display methods, and interactive functions are described. Some examples are also illustrated.