基于虚拟环境的黄河仿真系统构建

Three-Dimensional Simulation System for Virtual Environment in the Yellow River Basin

虚拟现实的产生和发展无疑为加强地理科学研究提供了强大的手段和方法上的支持。本文从虚拟环境的角度出发,给出了一个黄河仿真系统的建设方案,它包括数据源、三维仿真地形库、三维仿真模型库、三维仿真虚拟实现四大模块。然后详细探讨了黄河仿真系统的关键技术:①通过对三维图形开发工具OpenGL的原理、实现功能等的分析,提出了在黄河仿真系统建设中OpenGL技术的具体应用实现方法,实现了实时动态漫游;②基于MultiGenCreator的真实感三维模型建设;③利用OpenGL和MO来实现三维场景与二维电子地图的互响应;这充分发挥了三维场景与二维电子地图各自的优势,有机地结合了三维虚拟场景的直观性、现实性、局部性和二维电子地图的宏观性、整体性、简洁性的优点,同时又克服了三维虚拟场景漫游的方向迷失感和二维电子地图的抽象多义性。

Virtual Reality technology is a type of human-machine interface for simulating human behaviors such as vision, hearing and movement. With a 3D helmet, data glove, 3D mouse, data clothing and stereo earphone, people can be immersed in a special 3D digital graphic environment, and can operate within this environment to realize a given purpose. Traditional visualization methods include paper and digital maps which emphasize spatial data displays. In contrast, Virtual Reality, with the capabilities of multiple sensory immersion, interaction and autonomy, allows for 3D dynamic real-time map displays. By using Virtual Reality, not only can models be built in multi-dimensional data space but also high-level abstract knowledge can be acquired and new concepts can be formed by the user. The Virtual Yellow River System includes five major modules： data sources, 3D simulation terrain database, 3D simulation model database, 3D simulation implementation and an application system. Data sources included DEM data, terrain element vector data, geographical texture data, 3D model data and geographical element texture data. The 3D simulation terrain database was used for terrain scene display. The 3D simulation model database was used for 3D model display. The 3D simulation implementation was used for various kinds of mutual operation （such as Keyboard Navigation and Route Navigation） in the 3D scene. The application system enabled the realization of the 3D target management and the mutual response between the 3D scene and 2D electronic map. The data sources for the Virtual Yellow River System included 30m resolution ETM ＋ image of the Yellow River （September 2001）, 1：50000 DEM data of Henan Province, texture maps of Yellow River, the urban architecture layout of Henan, and building models and digitized maps. The data processing software included ESRI ArcGIS 8.3, ArcView 3.2, ERDAS IMAGINE 8.6, Maplnfo 7.0, Terra Vista 4.0, Muhigen Creator 2.5.1 and Adobe Photoshop 7.0. In the 3D navigation system, the viewpoint was the ＂avatar＂ of the eyes and its function was similar to a camera in the real world. Navigation in 3D space was a kind of 3D drawing process, constantly moving the viewpoint and changing the sight direction which could be oriented through the viewpoint position. So by constantly changing viewpoint and position, 3D scene navigation is actualized. Keyboard Navigation and Route Navigation are two typical kinds of 3D scene navigation. OpenGL technology was implemented to realize the real-time dynamic display. MO and OpenGL technologies were used to create the mutual response between the 3D scene and 2D electronic map. As a result the advantages of both the 3D scene and 2D electronic map were brought into full play. The macroscopic view, integration and conciseness of the 2D electronic map and the locality, reality and visualization of 3D seene were combined. Also, the disadvantages of abstraction and ambiguities of the 2D electronic map and the loss of direction in virtual navigation of the 3D scene were overcome.