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Figure 4. Extraction result of Figure 5. Extraction procedure of 
flattop fastigium house 
3.2 3D Reconstruction of House 
The extraction scheme of housing boundary mention above is based on the analysis of single image. House could be 
reconstructed in object space through extracting the corresponding house boundaries in the left and right image. But, the 
paper adopts the scheme based on the least squares matching with geometrical constraints in object space (Zhang, 2000). 
Based on the least squares matching of straight-line template, the scheme introduces the geometrical constraints in 
object space, which not only ensures the accuracy of the house reconstruction but also improves the reliability with the 
features of good noise resistance. 
4. Restoration of the visible surface texture of the house 
4.1 Determination of Visibility of Wall Surface 
Because the aerial image is central projection, the roof of the house is generally visible. But for the walls, some of them 
are visible, called visible walls. Some are shadowed, called invisible walls. The texture of the former can be extracted 
form the image while not of the latter. Therefore, it's necessary to determine the visibility of the walls to extract their 
texture (Figure 6). 
  
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(a) Object space (b) Image space 
Figure 6. Determination of Visibility of Wall Surface 
The corner points on each surface of the house (roof or wall) should be numbered in certain order, to ensure that the 
normal of each surface points to the outside of the house according to right-hand rule. Figure 6 (a) indicates that both 
normal F of the front wall and normal R of the right wall point to the outside of the house. When these wall points are 
projected into the image, the numbers of them should keep unchanged (Figure 6(b)). Now, the normal R of the 
projection face of right wall surface on image is upward, towards the projection center, and thus it is visible. The 
projection normal F of the front wall on image is downward, away form the projection center, and thus it is invisible. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 1019