CI PA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
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cameras. In the case of stones, white powders that can be 
sprayed on the surface and washed of with water afterwards can 
be used without causing any harm to these objects. 
The artifact is scanned with one end fixed by the plasticine. The 
result of the measurement is directly displayed (fig. 3, left). By 
rotating the object, further scans can be acquired without chang 
ing the relative position of object and reference points. Usually, 
5 to 7 individual views are needed to record the complete 
visible surface in the first object position. 
For a complete representation the individual views are merged 
into a single data set. With an automatic determination of the 
current sensor position, the system can transform the individual 
measurements into a common object coordinate system using 
the detected ATOS reference points. The result is the 3D mesh 
for the first object position. The part of the artifact covered by 
the plasticine must be measured subsequently in a second object 
position. 
Second object position. In order to allow scanning for the 
second position of the object, it is turned around and the other 
side is now held in the plasticine. Again, several single scans 
are acquired and combined to the mesh for the second position. 
Fig. 3. Left: Result of a single scan. 
Right: Combination of different scans. 
Now, the two meshes (first and second object position) have to 
be merged into one. Since there are no common ATOS refe 
rence marks available in this case, four or more common points 
have to be identified interactively on the meshed surface. In 
most cases, this is a very time consuming process; often it is 
impossible at all. Two-dimensional points like color marks can 
not be identified in the 3D views of the surfaces. After many 
experiments, including the construction of swiveling clamps, it 
was decided to mark four very small three-dimensional targets 
on flat parts of the object. Toothpaste proved to be an ideal 
material since it has the right consistency, high reflectivity and 
it can be removed without any problems after the measurement 
process. Thus, the identical points can be identified easily and 
quickly because the tooth paste peaks’ position is known be 
forehand and 3D features can be recognized easily in the mesh. 
can be filled without much quality loss since the peaks are very 
small and were intentionally placed in flat insignificant parts of 
the object. This completes the scanning procedure, and a virtual 
3D model of the object is now available (fig. 4). The whole 
procedure which includes scanning, registration, meshing and 
hole filling can be accomplished with the hard- and software 
supplied by GOM and takes less than 45 minutes per artifact. 
Fig. 4: Virtual 3D copy of a stone age artifact 
3.4 Thinning methods and storage 
The acquired virtual 3D model shows a very high point density 
resulting in large file sizes. This density is necessary to 
document the sharp edges; in parts with small and/or regular 
curvature, point density can be reduced considerably, however, 
without any recognizable quality loss. Using the ATOS soft 
ware itself or other software products like Geomagic Studio or 
qslim the mesh can be thinned intelligently. With qslim, for 
example, we could often reduce the file sizes by about 50%, 
with no recognizable differences when viewing the model. Of 
course, the potential of thinning depends a lot on the structure of 
the stone artifact’s elements. For the storage of the results the 
common STL file format is used. It can be read by most 3D 
viewers and 3D processing programs. 
4. VISUALIZATION 
4.1 3D viewers for 3D inspection 
When the measurement is complete and a 3D result is stored, 
archaeologists can view the data on a monitor (fig. 4). For this 
purpose, a viewer is necessary which shows the 3D result. With 
such a program (such as SolidView which is freeware in its 
light version), anyone can view the artifact and change viewing 
angles and lighting interactively. The virtual model can easily 
be inspected from all sides, much in the same way as the 
original stone object would be examined. 
After this pre-registration which merges the two meshes to- 4.2 Edge based visualization 
gether, an automatic 'Best Fit' registration improves the result 
and provides the final set of data for the whole artifact as an In a diploma thesis at FH Mainz (Tschoepe 2003) an attempt 
ASCII point cloud or in a polygon mesh according to the STL was made to classify and visualize local curvature on the object, 
format. If there are some small insignificant holes left, these can After a triangular mesh of the object’s surface is accomplished, 
easily be filled by the software. The toothpaste peaks which are every individual triangle can be furnished with an own texture 
still on the mesh are cut out and removed. The resulting holes when the OBJ format is used. The computer program developed