International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004 
  
  
the building models, is used; while ground images collected 
from handheld cameras are used for wall textures. 
3.1 Roof Texture 
The scanned aerial photo is used to create roof texture. To avoid 
many small image files, all building roof objects in the study 
area are associated to their texture images at one time based on 
the photogrammetric principle. The collinearity equations are 
involved in this calculation for image data retrieval. However, it 
is not efficient to associate the texture image to the roof object 
with rigid photogrammetric model every time when we display 
the building model. To solve the problem, we generated and 
used the ortho-rectified image in which the image values have 
the same coordinates system as building roof model. After that, 
we can define the relationship between images and 3-D building 
objects directly for texture mapping. The location of the image 
segment for a building roof texture in an aerial image and 
orientation are most important parameters to map the texture. In 
this paper, an ortho-rectified image, which has contents only 
inside each building boundary and contains null outside, is 
generated as building roof texture. This is accomplished by 
enhancing current ArcGIS with advanced photogrammetric 
capabilities to handle model based true ortho rectification. 
Figure 3 presents an example of such generated ortho image for 
roof texture. 
  
(b) 
Figure 3. Texture Images for Roofs (a) and Walls (b) 
3.2 Wall Texture 
The building wall pictures were taken on the ground to create 
the wall textures with a digital camera and a 35mm roll film 
camera. In case of roll film camera, we got the image after 
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developing and scanning using a desktop scanner. For the wall 
texturing, we use a different way with roof texturing. Each wall 
is related to one individual image file. In addition, the wall 
texture is directly corresponding with view plane without 3-D 
building model. The detail methodology about the 
correspondence between the wall objects and image files and 
the association with view plane will be discussed in next section. 
4. PHOTOREALISTIC MODELING 
Once the geometric models and texture images are prepared, the 
photorealistic building model can be generated using the 
ArcObjects programmed and embedded in ArcGIS for this 
study. ArcObjects are a set of computer objects specifically 
designed for programming with ArcGIS Desktop applications 
base on the object-oriented programming (Zeiler, 2001). We 
use such development to automatically select wall texture 
images and associate them to the geometric building model. 
Figure 4 illustrates the general procedure for generating a 
photorealistic model by integrating all necessary data. 
3D Geometric model 
Ortho-rectified 
Roof Texture 
    
Ground Image 
  
  
  
Photo-realistic 3D Model 
Figure 4. Photorealistic 3-D Model Generation 
with Data Integration 
After generating the 3-D geometric building model, the building 
roof can be textured using the ortho-rectified image segment 
that is generated with aerial photo image. The assignment of 
texture image to the right building objects is accomplished by 
using the geometric relations between 2-D coordinates of texel 
and 3-D coordinate of building model through the orthographic 
projection equation. Twelve parameters are required to 
represent the 3-D object on the 2-D view plane as shown the 
following homogeneous transform matrix (Hearn, et, al, 1994). 
In this matrix, 2 and v are pixel coordinates in screen, X, Y, and 
Z object coordinates, R rotation matrix with element Ri, / shift, 
@&% 44, and v intrinsic parameters and s and 7 perspective 
parameters.