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fitting a plane to the corner points, and a plane parallel to it at 
the surface point, the complete window or door can be 
reconstructed. For steps, sufficient seed points to compute the 
two side planes, plus one point on either side of each step are 
needed. Table 1 summarizes seed point requirements. 
  
  
  
  
  
  
  
  
  
Element Seed points 
Plane 3: non-linear 
Column 4: two on base, two on crown 
Window or door 5: 4 corners and one inside 
Block attached to a plane | Top corner points 
Arch 3: on front plus arch edge 
Steps A corner in either side 
  
  
Table 1: Seed points for some structural elements 
6. EXAMPLES 
Over the past year, members of our group took images of 
various interesting monuments in cities all over the world. The 
images were taken during routine tours without any advanced 
planning of where to take the images. We took the images just 
like any typical tourist, by walking around the monument and 
getting the best view under real conditions such as presence of 
other tourists, vehicles, and other buildings and objects. Several 
types of digital cameras and regular film cameras (digitized 
later) were used. The results were indeed very encouraging. 
Over 100 models were created in 6 months, each one usually in 
1-2 days of work by one person. The number of points and level 
of interaction and automation obviously varied significantly 
from one model to another. At least 8096 of the points were 
generated automatically. Seven examples [more at El-Hakim, 
2002] are presented here, each to illustrate specific feature. 
They are presented in wire-frame, solid model without texture, 
and solid model with texture. In some of the structures, we 
found dimensional information available in travel or history 
books. This information was not used or needed in the model 
construction, but was valuable in evaluating the accuracy. 
  
Figure 9: A Trinity Collage building with columns and steps 
Figure 9 shows a building on Trinity Collage campus in Dublin. 
This typical classical architecture includes columns, steps, and 
several other blocks. From only two images, the whole entrance 
is constructed from about 400 points of which only about 50 
seed points were measured interactively. 
Figure 10-A shows the Arc de Triomphe in Paris. The Olympus 
C3030 digital camera (3.1 Mega-pixels) was used (14 images). 
The arc measures 45 meter x 22 meter, as indicated in some 
tourist guides (accurate height was not available). We used one 
distance (the 22 meter width) to scale our model. From the 
model, the dimensions on the four sides were: 22 meter (fixed 
for scale), 22.06 meter, 44.85 meter, and 44.89 meter, an error 
of 0.28%. One should point out that the given dimensions are 
probably rounded off and the sides are not perfectly identical. 
The next example is the St. John baptistery in Florence (figure 
10-B). The Olympus E-10 camera (4 Mega pixels) was used to 
take eight images. The baptistery has eight sides. The actual 
dimensions were obtained from a plan in a book. The sides 
average about 13 meter in length. Again we assigned 13 meter 
to one side and used it to scale the whole model. 
  
  
  
  
  
  
  
  
Figure 10: Examples of constructed structures 
The average difference between the model sides and the actual 
sides was less than 1 cm, or 0.07%. This is significantly better 
than the accuracy of the Arc de Triomphe. This is due to the 
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