Research On 3DGIS Testing System Based On Virtual Reality Technology

The geospatial informatization has become a mainstream in information science development. Currently, the three-dimensional (3D) GIS combined with the virtual reality (VR) technology has been one of hot research topics in particular. On the one hand, the VR technology can help overcome some disadvantages of GIS in the aspect of visualization. On the other hand, GIS can provide functionality for VR such as inquiry, analysis which VR lacks.Selecting a campus circumstance as testing site, this thesis aims at developing a campus 3D GIS testing system based on virtual reality. It uses virtual reality to build 3D GIS and examines the integration approach of virtual reality and GIS. The main contents of this research are constructing the campus 3D scene models, implementing drive and roam of virtual scene and developing basic GIS functions by using some relevant modules and external interfaces.In the aspect of 3D modeling, this thesis compares and analyzes the application level and functional scopes of all kinds of 3D modeling methods, and proposes the scheme of virtual campus model creation based on Multigen Creator. Based on these, it completes the setting of scene level and structure and creates a compact and highly effective model database, and thus meeting the requirements of real-time drive and roam. In modeling, some key problems in model-position acquisition and complicated model creation are solved by using Creator and other multiple tools. Through a series of procedures such as data processing, 3D modeling and texture mapping, a vivid 3D virtual scene of Southwest Jiaotong University is built. Finally, some optimized operations are completed by making use of texture replacement, external reference, instance tools and level of detail. The model data structure is also optimized according to its running characteristic, and thus enhancing the roam efficiency.In the aspect of scene driving, this thesis compares the characteristics of two driving platforms, i.e., Vega and Vega Prime, and analyzes their respective pros and cros in terms of application program interface, scene-graph database, graphical user interface and etc. Based on the analysis, Vega Prime is chosen as the platform of campus scene driving. Then detailed are the basic modules of Vega Prime, including the interface of Lynx Prime and VSG API. Some basic functions such as collision detecting, scene driving and roaming as well as environment varying are finally implemented by using graphical interface, i.e., Lynx Prime and by establishing dynamic observation system, adjusting motion mode and adding collision detection. By using the API of C++, some 3D roaming functions are further augmented. The 2D-map addition and the mutual response between 2D and 3D are therefore performed and an application program based on MFC is developed.In the aspect of implementing 3D GIS functionality, how to integrating VR and 3D GIS is preliminary investigated. By making use of GIS software, a campus 3D GIS testing system based on VR technology is developed through a series of procedures such as importing model, editing model information, defining switch mode and etc, and thus achieving the purpose of integrating VR and GIS. Some functions like interactive query, inter-visibility analysis and geometric measurement are eventually implemented.The research conducted through the testing system shows that it is effective and economical to build a VR-based 3D GIS. Such system can provide services for virtual scene browsing and GIS operating. This indicates that it is feasible to develop 3D GIS with use of virtual reality technology, and thus providing an efficient and viable approach for the future 3D GIS development. Such 3D GIS system has a great application potential in the fields of mining engineering, military affairs and city planning.