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We can display the 3-D building object with texture 
conveniently using perspective projection based on viewing 
angles and scale after the. relationship between building 
geometric model and ortho-rectified image is prepared by the 
method mentioned before. The rendering result is shown in 
Figure 5a, where the ortho-rectified roof image is used as 
texture and overlaid atop building model in ArcScene. 
However, this data structure is not adequate to represent the 
texture for both roof and walls at the same time in ArcScene for 
display. ArcScene doesn't support the PolygonZ format that we 
chose for storing geometry model of the buildings to display if 
it has several patches belong to the same object. Therefore, we 
cannot use the rendering class of ArcScene for wall texturing 
although the shapefile contains the geospatial information of 
vertical walls. They need to be treated separately. 
  
(b) 
Figure 5. Textured Building Roof (a) and walls (b) 
To display wall textures, we add a graphic layer to represent the 
texture of vertical wall. That layer is generated only for 
visualization and has no concern about data structure or query 
because it doesn't have any attribute data and geospatial data. 
All information about the vertical walls is contained in the same 
shapefile that includes the polygon data for the roof. Using the 
spatial data about building wall in building layer, we create the 
wall polygon temporarily and associate the texture with that 
polygon. After that, we get the parameters that relate the texture 
image with the view plane using the same way as roof texturing 
and then we change the polygons with texture into graphics and 
save them. This process is repeated until every wall texture of 
entire building is generated. The next step is then to link the 
image file to the appropriate wall. Taking pictures of all 
building wall in the study area is almost impossible and 
unnecessary practically. Therefore, we categorized the building 
walls according to the material, color, and the height-width 
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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004 
ratio. Three types of walls are used in this study: dark red brick, 
light red brick, and gray concrete with various sizes. 
ArcObjects for 3-D photorealistic building modeling can select 
and assign the wall texture images, which are grouped already, 
to the temporary wall object automatically. That program 
calculates the ratio of height and width of image and then 
compares it with ratio of facade for vertical walls. After it finds 
out the façades that have most similar ratio, the image is 
textured on it. Figure 5b is the result with both roof and wall 
textures being rendered. 
Once the 3-D model is built, we can load this model into 
ArcScene or other commercial GIS software that use the 
shapefile format. The advantage of this is that we are able to 
use the whole functions which are already existed in the 
commercial GIS software such as changing view point, 
shadowing, adding and combining data and so on. The building 
model can be added to city model and become more realistic 
using those functions. 
The entire procedure mentioned above is applied to create a 
photorealistic virtual model for the Purdue campus in West 
Lafayette. During this process, the textures for the walls are 
selected automatically according to the conditions mentioned 
earlier. After that, the terrain model is generated with aerial 
picture and DEM (Digital Elevation Model). Finally, the virtual 
model for Purdue campus shows up through integration of 3D 
building model and the terrain model. Figure 6 shows the 
textured buildings in a closer view. This picture shows the 
image textures fit into the building models well both in the 
corner area and in the central area of the entire campus model. 
Figure 7 represents the campus model at the ground level view, 
while Figure 8 is the panorama of the campus model. The result 
is more realistic if appropriate texture were selected through 
manual editing and more texture groups were used according to 
color and material of walls. In case of landmark such as a tower 
and a statue and environmental objects such as tree and rock, it 
might be hard to model and texture them with current data 
model and texture mapping methods. They need to be modeled 
separately and will be considered in future study. 
  
   
  
( b )Figure 6. A Corner of the 3-D Photorealistic Model for 
Purdue Campus (a) and Close View of Textured Building (b)