Research And Exploitation Of 3D GIS Based On OpenGL

The people are quite eager to process geographic issues in terms of the angle of real three dimensional (3D), as the application of two dimensional GIS (geographical information system) penetrated deeply. At the present time, appropriative 3D GIS products with segmental function have been developed in industrial territories such as mining, geology and petroleum.So far mature and integrate 3D GIS system has not emerged yet all around the world. The other systems that are interrelated with 3D GIS, such as 3D Max, Maya, EVS, Vis5D, Voxel and medical visualization, mostly concentrated on the application of 3D visualization. There are some 3D systems partially achieve functions of 3D GIS, including some famous software like LYNX,IVM(Interactive Volume Modeling),GOCAD,I/EMS,SGM.This thesis concentrate on the research and exploitation of 3D GIS based on the functions of 2D GIS. The author has noticed the present 3D GIS or other 3D products mainly emphasized the images, the third dimension of graph and the feeling of lifelike, instead of studying and exploiting 3D GIS base on the functions. The essential function of GIS is property inquiry towards ground object, to reveal exact position of ground object according to the property information, and the spatial analysis. But the current exploitation of 3D GIS is weak. The author wants to study and exploit 3D GIS based on the functions of 2D GIS, using underground pipe networks as model. The author expects the 3D GIS develop from visualization to fictionalization.What follows is tangible content of this thesis. Generally speaking, the research content and exploitation content includes six respects as below:(1) The establishment of three dimensional scenes in 3D GIS. As we all know the 3D visualization of ground object requires 3D scene with 3D perceptivity. That is the issue should be considerated primarily. This thesis establishes 3D scene system, which is needed by ground objects 3D visualization, by using MFC and OpenGL(2) The author exploited the functions including enlargement, reduction, translation, panoramic view zoom and rotation in 3D scene. Among others, rotation is particular function of 3D GIS, it is also the most valuable function of 3D GIS. For example, it is hard to determine the position relationship between underground pipe networks in 2D GIS, this doesn't sometimes even though in 3D GIS, but it is easy to achieve this target by using rotation function of 3D GIS.(3) The research on the issue of the management and design of spatial database. There is substantive data which need organization and management, including attribute data, spatial data, and model data. The organization and management of above data is a momentous issue.(4) The construction of model library in 3D GIS. Plentiful models of ground objects are need, because OpenGL just supply 3D perspective space without models. Instead, developers have to structure vast models by themselves. The management and use of these models is the 4th issue the author considerated.(5) The author has implemented the selection and feedback inquiry in 3D GIS. How to examine the attribute data by selecting a particular ground object and how to get the exact position of a particular ground object by selecting a item of record in datasheet is the essential function of 3D GIS in author's view. This function is also the essential difference between 3D GIS and 3D Max, Maya.(6) The research on the illumination model in 3D GIS. The application of illumination model is important in 3D GIS. Illumination model is a intricate model that seems ordinary, but perplexing in practical application. It also brings unexpectable troubles. For example, a red object wonn't has third dimension until the illumination is added. But after the use of illumination, the hue information of that object will lost or fade away. This issue is worthy of research, this thesis discussed this topic.At last, the author provided a 3D GIS primary software that has functions above. A 3D GIS framework is structured after achieving six issues above. The remaining task is further and delicate work on it.In brief, it is a challenging work for studying and exploiting 3D GIS using currently advanced technology. This work requires abundant knowledge which is whole new for us probably, even we just know its name without understanding. We need challenge.