Creating 3D city from the geographical information is an important goal in the field of visualization for GIS and the needs for Web GIS are growing and expanding rapidly. Many scenes of the 3D cities are built based on the models which are made by computer aided designing software to present real scenes, however, this method costs too much time and labor with the low efficiency. This paper presents a method that can promptly construct a 3D city on the Web according to the geographical information. Our approach uses the descriptions for the city from the geographical and additional information to construct the scene and divides the buildings into "molecule parts". With the bottom-up process from cursory objects to fine buildings to assemble the whole scene, the patterns correspond to Web environment which needs the distributed data management and gradual transmission. Ever divided part which can be classified into the common types and saved into distributed storage environment is constructed according to its characteristics. In addition, we first establish abstract databases to store and classify various "molecule parts" which are created based on geometrical arithmetic, common objects and small models. The descriptive information specifies the data from database, which just need loading rather than producing, with lower cost of time and labor. Our approach designs a processing assembling method to match the different parts of building and the level of matching can be elaborated further with the expanding interfaces. Our approach shares and reuses the resources for rendering, such as geometrical structures, materials, textures and even the small models, to diminish the amount of data and the influence of network delay. Experimental results show that our approach increases the speed for rendering and decreases the transmission capacity greatly. Our approach is appropriate for the Web environment to improve the rendering efficiency and for promptly creating a 3D city.
