实现三维地形模型的彩色光照和动态显示

THE REALIZATION OF 3 D TERRAIN MODEL ILLUMINATION AND DYNAMIC DISPLAY

介绍了一种具有真实感的三维地形模型的光照显示实现方法，给出了构建高精度数字高程模型ＤＥＭ的具体步骤，讨论了ＤＥＭ的多种精度表示、三维地形模型光照显示中的消隐、可见性测试及光照模型等处理算法。

Three dimensional terrain illumination and dynamic display can be realized by two technical methods. One is the image model which is calculated and displayed in real time according to visual orbit. The other is that the image is precalculated with illumination model and the processing results are recorded on the medium. Then its displayed on the screen continually. The study results are implemented by micro computer and windows environment. 3 D visualization is a key technique that improves the ability of analyzing and processing geographical information and extends the expression form of map. As an important technical method , 3 D terrain model illumination display makes full use of the imformation of terrain isopleth and other geographic features ,such as road,river,lake,border and so on ,to create high quality DEM and corresponding level digital model of geographic element, and aquire high quality terrain illumination image by adopting multi resolution expression of digital model. Depending on view's moving orbit ,optical condition and terrain surface material, we use compact GIF image form to precreate successive frame images and store them in computer. When displyed, these GIF images will be read and released and put on screen frame by frame in appropriate speed to create dynamic terrain image. The realization of three dimensional terrain model of illumination and dynamic display that is of the most realistic is now proposed by the author. The procedure of creating highly precise DEM is given and processing algorithms appropriate to 3 D terrain model, such as DEM Level of details ,illumination model,hidden surfaces elimination and visibility test, are discussed. Furthermore,dynamic display method of 3 D terrain model approprite to micro computer is also described in this paper. The methods discussed in this paper have been successfully tested in our research area. The new technique of dynamic and illumination display of three dimensional terrain model can provide visual and distinct terrain model directly and actively .This technique method can be widely used in various areas, such as terrain analysis,site design,landscape analogue,simulated war theatre and so on.