3D Visualization of Tree Model
树模型的三维可视化研究

The 3 dimensional visualization of a tree model is a difficult problem,especially in GIS field Spatial characters of trees have great differences from common objects It has clear fractal character,and it's difficult to establish data model using common modeling methods Now,fractal theory is in use widely,and it could produce vivid effect However,the data amount is very large for 3 dimensional visualization in GIS Tree image is used more widely than that of tree model,but in the near viewpoint,tree image would have a bad effect because the essential characteristics of a tree are ignored in this way In this paper,the advantages of the modeling and Level of Detial(LOD)technology have been used Our modeling scheme is to use a tree 3D model produced from fractal algorithms This model is managed by BLOB type in database because it is difficult to do spatial analysis using fractal model One cuboid could envelope a tree model in spatial analysis process and in visualization process Tree fractal model could only be used in very near viewpoint Multi solution tree images are used to express trees in different view distances Theses images are also managed using BLOB data types in database Same cuboid in fractal model is also used in spatial analysis Fractal tree model and multi solution tree images are combined by a fix LOD division in visualization process according to system design or user selection LOD division is referred to view distance and tree images solution At the end of the paper,our experiment system is introduced It shows that our method could be used to solve 3 dimensional visualization in city environment in tree model,and have a good effect