Research Into The 3D Flood Risk Information Visualization Based On OpenGL

China is a country that suffers from the flood disasters frequently. Every year, the losses caused by the flood disasters are over 60% of the whole natural disaster losses. It directly affects people's lives, property and social stability. Improving the flood control capacity of the river basin is mainly through project and non-project measures. Compared to the project measures, non-project flood control measures have shorter construction period, less investment and quicker effects in flood controlling system, and play an increasingly important position. Flood hazard map is one of non-project measures. This paper puts study emphases on flood risk information visualization which is an important part of flood hazard map. The three dimen-sional model constructed by OpenGL can directly reflect the flood risk information, and this paper achieves the three-dimensional interactive real-time roaming of the flood and terrain, and provides scientific basis for the policy-makers making decisions to prevent floods.This paper jions the geographic information system and visualization technology together depending on their functionalities and features, and achieves the flood risk information visualization. The contents of this paper mainly include:(1) Through the methods to construct 3D objects'model, the realism display technologies and interactive control technologies provided by OpenGL, this paper makes a 3D objects visualization system based on OpenGL which uses VC + + as the platform. This paper vividly display the regional flood risk information by this system.(2) According to the characteristics of raster data in ArcGIS, this paper uses regular grid digital elevation model, the color control, blending and texture and other technologies to realize the 3D realistic simulation of terrain and flood. Its realistic simulated result is better than ArcGIS'. It achieves a true representation of the flood advance by the computer animator.(3) In the paper, the data used for simulating embankment is vector data of ArcGIS. Because of the different ways to organize the vector data and raster data, the methods used to simulate the 3D objects are different. According to the structure characteristics of the embankment, built it's mathematical model, solve the key point of embankment simulation, use parameterized modeling method construct the 3D model of embankment, and complete the seamless amalgamation between embankment model and topographical model. Watercourse surface uses quadrilateral to approximate simule and utilizes the computer animator to make the water flowing from high field to low field. All of these increase the sense of 3D reality for the scene.(4) Resolving the display problem of large-scale terrain and flood through fog technology. This technology creates a limited visibility area which greatly reduces the number of tri patches needed to simulate and the burden of the graphics processing system. Furthermore, when supplying pictures'scene of the reality, it improves the display speed and implements real-time interactive 3D roam for the flood and terrain unconstrained by line and sight.The article fully exerts powerful spatial analysis and data management function of the geographic information system, and the function to build 3D realistic model of the visualization techniques. Make two of them complement each other and promote each other which can well simulate flood risk information. Cover the ArcGIS'shortage on 3D realistic display and help policy-makers timely and accurately making decisions to reduce the flood loss.