6. APPROACH TO THE AUTOMATIC RESTORATION 6.2 Search of adaptation of the cross section 
At present, though it is possible to restore a relic from 
fragments in virtual space, the restoration task is only moved 
from real space to virtual space. Though no damage is given to 
virtual fragments at all, the restoration task is still done by the 
manual operation. Under the present circumstances, the increase 
of the restoration task efficiency cannot be expected. Then, the 
automatic restoration is desired. As an approach for the 
automatic restoration, followings are regarded. 
• The expectation of the relics by the nature of the soil and 
the find site. 
• The utilization of the curvature of the model. 
• The resemblance between cross sections of two 
fragments. 
This knowledge is important with the restoration work but it is 
difficult for the computer to use this knowledge. The restoration 
task is usually done by exploiting, features obtained from the 
cross sections of fragments in the real space. And, much more 
precise information on the cross section of each fragment can 
be obtained with X-ray CT rather than the laser measurement. 
Therefore, we aim at the automatic restoration based on the 
former strategy. 
6.1 Cross section & point extraction 
It is necessary to extract the cross section of a fragment in order 
to find a counter part. As extracting method, normal vectors of 
the cross section are used. The normal vector is a perpendicular 
vector to the surface. In comparison with the normal vectors of 
the neighbors by extracting one with different angle, the cross 
section can be found as shown in Figure 16. 
imuir 
(a)abrupt vector (b)smooth vector 
Figure 16. Cross section definition 
However, this method extracts the cross section as a cluster of 
points. To create list structure automatically from the point 
group at present is a difficult problem. Because this problem 
seems to be solved in the other field, we create list structure by 
the manual operation. 
If a counter part is selected among the all other fragments using 
the cross section information, the system will suffer from the 
inefficiency. Then, to aim only at the cross section information, 
we define a rapidly changing point as a cross point. Figure 17 
shows a cross section & cross points of the fragment. 
Figure 17. The cross section & point 
When we restore the relic, the tendency that relic is restored by 
the pair is strong. When restoring more than two as shown in 
Figure 18, a pair isn't often made. Therefore, it is possible to 
discover a pair efficiently using the cross point. By re-forming 
cross point after assembling fragments, the new pair can be 
discovered. 
Figure 18. The order of a counter part 
Using the normal vector, we search a corresponding cross 
section with pair. When the amount of the normal vector in the 
mutual cross section becomes 0, we define as the corresponding 
cross section. 
6.3 Automatic restoration example using the cross point 
We do automatic restoration using the cross point. We measure 
the curve distance value of the cross section which is caught in 
the cross point as shown in Figure 19. The numerical value of 
the Figure 19 is the curve distance value of the cross section. 
Because we cannot search the right cross section, we cut off a 
curve distance below 100 pixels. We compute the amount of the 
normal vector in the cross section with near curve distance 
value (±5%). 
© 
Figure 19. The automatic restoration example by using a 
point: 1 
The search in the cross section with near curve distance value 
was 19 patterns. By worker's excluding fragments with different 
thickness, we chose 5 patterns as shown in Figure 20. 
Moreover, we got the result as shown in the Figure 21 by more 
searching. Then, we find that the [2,7] pair of the Figure 20 is a 
mistaken result. Because the computer can handle overlapping 
fragments, the trial and error is easy. In the last, we got a result 
as shown in Figure 22. 
The error is bom whenever continuing restoration, and cracks 
are built. However, by this automatic restoration result, we can 
imagine the whole shape of relic. By getting a relic number 
from this automatic restoration result, this system is useful as 
the restoration simulator. 
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