Research On Three-dimensional Scene Construction Technology Of "International Biological City"

At present,most of the researches on 3D visualization of digital city tend to be oriented to the construction of large-scale 3D scene.Because of the wide range of modeling,many details are ignored,and the rich details of urban space can not be expressed.No matter from the view of three-dimensional city viewing or thematic research,the three-dimensional expression of urban space should be carried out deeply from the micro-level at the same time of macro-control.The construction of high-precision 3D scene with more details as the focus has become a new pattern of 3D information expression in urban space.At the same time,it is facing new challenges on the technical level: the structural complexity of urban landscape elements is different.In the face of high-precision model construction,if a modeling method is adopted,the modeling difficulty coefficient is large and the modeling cost is high.Because the high-precision terrain data is difficult to obtain,the existing low-precision terrain data does not coincide with the terrain model in the three-dimensional integration.Based on the above challenges,The main research results are as follows:(1)According to the structural characteristics of urban regular building elements,because of its small modeling difficulty coefficient,strong regularity and small memory occupation,the 3D model of regular building based on 3DSMAX modeling method is studied.The model not only covers a small number of surface elements,but also meets the accuracy requirements of fine modeling.(2)In view of the problems of large modeling difficulty coefficient and complex texture mapping of complex building elements,a modeling method based on digital close-view photogrammetry technology is introduced,and key algorithms such as space-three encryption and semi-global matching,which are supported by multi-view geometric theory in photographic measurement modeling,are deeply studied.And based on the figure image data,the three-dimensional model with high precision of complex elements is automatically generated.The method can effectively solve the problem that the difficulty coefficient of the complex ground object modeling is large,the modeling efficiency and the mo-deling quality are improved,and the method is applicable to the construction of a high-precision model of a complex ground object.(3)The matching method of terrain and ground object based on feature constraint is studied,and the problem of incoincidence between terrain data and ground object with low precision is solved.On this basis,the improvement is that the criterion of non-end intersection and the optimization of local terrain around the feature point are added after embedding the feature line.After optimization,there is no large elevation difference around the coincidence part of terrain and ground object and its connection is natural.The matching results between terrain and feature elements show that the effect of this method is remarkable.(4)On the basis of the existing project data,the construction of three-dim ensional scene in urban space is realized.This paper discusses in detail the construction method of each element model of urban space,points out the problems faced in the integration of 3D scene,and puts forward some solutions to complete the construction of high precision 3D scene.Finally,based on the constructed 3D scene,combined with TerraDeveloper development interface,the research and development of 3D visualization analysis system of International Biological City is realized,including 3D scene browsing,spatial measurement,spatial information query,spatial analysis,air quality query and so on.