三维地形模型的网络传输及可视化研究

发布时间：2018-02-25 19:36

本文关键词： 网络化应用地形绘制实时传输地形可视化　出处：《南京师范大学》2013年硕士论文　论文类型：学位论文

【摘要】：SAAS (Software as a services,软件服务化)是21世纪新兴起的一种软件应用模式,在SAAS模式中,用户仅需通过浏览器就可实现软件应用。应用程序网络化是实现SAAS的前提,实现单机高效地形可视化算法的网络化应用,对于基于SAAS模式的数字城市建设具有重要意义。相对于网络二维地图,网络三维地形场景具有符号简单、生动逼真特点,但基于网络的三维地形场景可视化研究,受到地形数据量大、地形传输耗时、客户端插件等问题的困扰,软件服务化发展较慢。本文针对上述研究难点,做了如下几个方面的研究： 1)研究了目前主流高效单机版地形绘制算法——GeoClipmap,在GeoClipmap算法中,每一层LOD (Level of Detail)的数据量是可控且有规律的,具有渲染帧率稳定的优点。本文根据GeoClipmap的规则网格嵌套特性,设计了新型的适用于网络传输的GeoClipmap坐标系以及裁剪机制,利用该坐标系及裁剪机制,根据Clipmap原点,客户端能够快速重构出地形网格的X、Y坐标,相对于传统传输完整地形顶点数据结构的方法,本文方法达到了8倍的压缩率。 2)对于地形模型的实时传输,本文从底层扩展设计了WebSocket数据帧结构,并采用WebSocket进行地形网格数据实时传输。通过扩展数据帧结构,实现了以Clipmap层为单位的地形数据实时传输。另外充分结合WebSocket协议小数据包报头特点,可以减少模型传输时间和增加3D模型可传输量。 3)对于客户端地形绘制,本文在免安装插件情况下,设计了一种构建三角条带的新方法,地形网格数据传输至客户端后,通过在每一条三角条带头尾添加退化三角形,将方形网格转换为一条三角条带进行绘制,进一步提高了地形绘制速度。通过上述三方面研究,本文设计实现了面向网络的免插件地形传输及可视化原型系统,验证了GeoClipmap算法网络化应用的可行性,本原型系统中,每一层255×255地形网格的数据传输量由0.49M减小至0.06M,数据量减少87.8%,相对于GeoClipmap算法,数据量减少51%,大大提高了客户端地形可视化速度。
[Abstract]:In 21th century, SAAS Software as a service is a new software application mode. In SAAS mode, users can realize software application only through browser. Application networking is the prerequisite of SAAS. It is very important for the construction of digital city based on SAAS mode to realize the network application of high efficiency terrain visualization algorithm on single computer. Compared with the two-dimensional map of network, the network 3D terrain scene has simple symbol, vivid and lifelike features. However, the research of 3D terrain scene visualization based on network is beset by the problems of large amount of terrain data, time consuming of terrain transmission, client plug-in and so on, so the development of software service is slow. The following studies have been done:. 1) GeoClipmap-the main effective single-machine topographic rendering algorithm is studied. In the GeoClipmap algorithm, the data of each layer of LOD level of detail is controllable and regular, which has the advantage of stable frame rate rendering. According to the regular mesh nesting characteristic of GeoClipmap, A new GeoClipmap coordinate system and its clipping mechanism suitable for network transmission are designed. By using the coordinate system and clipping mechanism, the client can quickly reconstruct the XY coordinate of the terrain grid according to the origin of Clipmap. Compared with the traditional method of transmitting complete topographic vertex data structure, the compression ratio of this method is up to 8 times. 2) for the real-time transmission of terrain model, this paper designs the WebSocket data frame structure from the bottom layer extension, and uses WebSocket to carry out the real-time transmission of terrain grid data. The real-time transmission of terrain data based on Clipmap layer is realized. In addition, combined with the characteristics of small packet header of WebSocket protocol, it can reduce the transmission time of the model and increase the transmissible amount of 3D model. 3) for client topographic rendering, this paper designs a new method of constructing triangulation strip without installing plug-in. After the topographic grid data is transmitted to the client, a degenerate triangle is added at the beginning and end of each triangulation strip. The square mesh is transformed into a triangular strip for rendering, which further improves the speed of terrain rendering. Through the above three aspects of research, this paper designs and implements a network-oriented terrain transmission and visualization prototype system, and verifies the feasibility of the network application of GeoClipmap algorithm. In this prototype system, The amount of data transmission in each layer of 255 脳 255 terrain grid is reduced from 0.49m to 0.06m, and the amount of data is reduced by 87.8 meters. Compared with GeoClipmap algorithm, the amount of data is reduced by 51m, which greatly improves the speed of terrain visualization on client side.
【学位授予单位】：南京师范大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：P284

【引证文献】