Study Of Three-dimensional WebGIS Visualization Based On Flash Technology

Currentlly, the means to achive three-dimensional WebGIS visualization is generally based on plugins installed on the client browser. However, these plugins usually have low market share, and difficult to Marketing, some even can not be cross-browser or cross-platform. This has been greatly restricted the development of three-dimensional WebGIS applications.According to the main problem for the current3D WebGIS client visualization, this paper proposes using flash technology to achive the visualization of3D WebGIS on the client. Flash client with its excellent market share, cross-platform, cross-browser and the excellent showing the effect of the interface, has bean used wildly to create two-dimensional in WebGIS applications. It must be exciting to hear that the Flash Playerll was announced in the2011, which has a new ability named Stage3D. Stage3D allows flash to take advantage of GPU hardware accelerated and greatly enhances the3D rendering performance of the Flash client, which brings the possibility to use the Flash client to achieve the visualization of three-dimensional WebGIS.The paper explores the method of using flash technology to achieve the visualization of three-dimensional WebGIS. The specific research works include:1. Made an in-depth study of Stage3D, which is a new feature in Flash Player11. Throught analysising its GPU acceleration principle and the methods to build three-dimensional models with its api,it carried out a detailed research and analysis on the architecture of Away3D which is an open source3D engine based on Stage3D.2. On the basis of the two-dimensional open-source WebGIS application OpenScales, as well as the map tiling and index system in Mercator projection, the author designs a3D earth modeling by using the flash3D engine. Then with the help of ShareObject which is the flash local cache technology, a mesh caching strategy is designed to optimization the3D earth model. The texture mapping of the earth model is also discussed, and additionally a method is designed to help to manage the abtain of map tiles. Finally, the author gives a detailed study of the zooming and panning operations of the3D earth model.3. Based on the analysis of two ways to achive three-dimensional terrain visualization, this paper get a detail study of the Roam terrain algorithm which is based on regular grid, and then explore the method of using Flash3D engine to achive three-dimensional terrain visualization. The other hand, the study proposes a method to achive3D Virtual simulation by uploading of the three-dimensional model to the3D scene with Away3D api, and finally the interaction of the three-dimensional scene is discussed.4. A simple prototype test application based on the theory is designed, in which the content of the research is to implement and test. Throught the animation frames while the application during operations, it tests the3D rendering performance of the Flash client. Finally some analysts is done to the test result, which verifies the feasibility of using Flash to achive visualization of3D WebGIS on client.