Toward the automatic restoration of relics from slice images

The research of a relic excavated from remains has become popular. But a laser measurement device is mainly used for measuring shapes of fragments and can't measure uneven complicated shapes. So the X-ray CT (Computed Tomography) to make 3-D measurement possible has begun to be used as a measurement device, but the model generation needs the hand of man still more. We have already reported a basic restoration system with MRI (Watanabe, 2000) and a procedure to automatically recover surface models of fragments with complicated shapes from slice images measured with X-ray CT (Watanabe, 2001), and models restored with the system are useful to visualization or simulation of relic restoration. Though relics are never damaged by the restoration task in VR, so far the restoration task is done by the manual operation as long as we manipulate the relic fragment in virtual space. It is too inefficient to use it as the restoration simulator, because efficiency improvement of restoration task can’t be expected. Then, the automatic restoration is desired strongly. The precise shape information of a cross section of each fragment can be easily got with our method using CT. Therefore, we aim at the automatic restoration using the information. Because the surface model has only surface information, we define cross section using normal vectors in the fragment surface, and extract cross section. As the extracted cross section is not a line but an aggregate of points, a list structure of a line enclosing the cross section must be extracted using a thinning operation. A pair of cross sections is tested if their list structures are matched each other, and a pair of cross sections is matched when the summation of the normal vectors in one cross section is approximately equal to another one. However, it is very difficult to search out all cross sections. By defining a rapidly changing portion of a cross section as a cross point, we can search a corresponding cross section easily. The precision of automatic restoration is below that of manual one.