Research And Application Of 3D Visualization Of Urban Underground Pipelines With WebGL

In order to ensure the fast development of city,the underground pipelines should be efficiently and stablely managed.As pipelines are often buried underground and invisible,the it's very important to display them by using 3D visualization techniques.At present,the 3D pipeline network visualization systems in Browser/Server(B/S)mode mainly use third-party's plug-ins or are developed by using some common-used GIS software platforms,and this may require users to install third-party plug-ins,which generally leads to a heavyweight system and demand a relative long response time.As a new generation of 3D graphics rendering technology for browser-based clients,Web GL is plug-in-free and open structured,and it can be used to develop lightweight 3D pipeline visualization techniques.This paper studies some key techniques for 3D visualization of urban underground pipelines with Web GL,and aims to build a browser-based 3D pipelines management system.The main contents of this paper are listed as follows.Based on the existing method of 3D pipelines network model built and status of 3D pipelines system,this paper studies the classification and distribution characteristics of underground pipelines,and the pipelines are simplified and divided according to some modeling principles,and a method is used for fast building 3D pipelines network model by using 2D vector data.Firstly,the point and line symbols for the pipe points and segments are modeled by using 3DS MAX,then imported as map symbols into a SuperMap symbol library.Secondly,some parameters such as line width,height pattern,buried depth,coordinates and rotation angle,are chosen as the adaptive rendering parameters as they are crucial to render the pipeline network objects in vector format into a 3D scene with SuperMap' APIs.The experiments show that the 3D pipeline visualization is effective by using a method of fast modeling,and the underground pipelines are visually displayed.Based on the 3D pipelines network model are fast built,this paper designs a rendering scheme of 3D pipelines network scene data with Web GL.Firstly,the 3D pipelines network scene data(underground photogrammetry model and underground pipeline model)are obtained.Secondly,and these scene data are organized by using the S3 M data format with Web GL,which are published and stored by using web server.Finally,as the bandwidth is limited with web transmission,a scene cropping algorithm and multiway trees data scheduling algorithm is researched,and the algorithm could determine the visible area of target scene,and achieve efficient rendering in Web GL.The experiments show that the data cropping and scheduling algorithm could quickly update scene features according to the current viewpoint range when scene is switched,and achieve the principle of on-demand loading.Based on the above key technologies,in this paper,a 3D pipelines management system is built,and achieve the query and space analysis of pipelines.The system includes the following functional modules,visualization module,scene control module,measurement module,query module and spatial analysis module.Moreover,the system could provide a technical measure for planning and management of city.