International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004 
  
  
Figure 8. Bird View of 3-D Photorealistic Model for Purdue Campus . 
5. CONCLUDING REMARKS 
This study has successfully integrated photorealistic 
visualization capabilities into a 3-D GIS. Some useful 
experience is gained through this process. First, a 3-D 
geospatial geometric model needs to be carefully selected 
based on the multiple considerations, such as the definition of 
3-D geometry and topology, support of geospatial query, and 
effective texture mapping. It is shown that PolygonZ structure 
is an appropriate choice that can accommodate all the 
considerations with certain amount development and 
enhancement. Next, texture mapping is a crucial step in 
photorealistic visualization. In our study, a model based ortho 
rectification is developed to produce true ortho image based on 
building models. In this way, all building roofs can be easily 
mapped to the texture to achieve an effective 3-D rendering. 
Third, we successfully achieved an automatic association of 
building walls to their corresponding textures. This 
significantly reduces the amount of time for texture mapping, 
which is usually carried out manually. 
Future efforts will be made to improve our work. Other 
possibilities in effective 3-D data model will be explored to 
further simplify the texture mapping and rendering operations. 
Another problem is the consistency between roof texture and 
vertical wall texture in terms of color, resolution, contrast and 
spatial accuracy. In addition, we will make development to 
include more complex geospatial features and other geospatial 
information. 
20 
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