In this article we discuss the methods of 3d tree modeling by iteration function system ( ifs ) and l system based on the fractal . at the same time , we compare the two methods from the application of tree modeling in 3d cis and give the class definition of tree object from the object oriented point of view , in order that the tree object can be applied in 3d gis . all this research find a new and effective way for the visualization of tree in 3d gis 同時,針對樹木實體在3dgis中的應用,對兩種建模方法進行比較,確定l系統(tǒng)是3dgis中構建樹木實體的最佳方法,并從面向對象角度出發(fā),給出基于l系統(tǒng)的樹木實體類,從而使樹木實體作為3dgis中的對象之一融合到系統(tǒng)之中,為3dgis領域中關于樹木實體的表達尋找到一條新的而且是更有效的解決途徑。