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Digital archiving of Kamegata-Ishi(Turtle shape stone) using data fusion of heterogeneous measurements Integration To obtain a detailed shape of the entire stone, local shapes have to be placed on precise position in a skeleton of an entire shape. This registration is achieved through the process that matches each marker of the local shape to the corresponding marker of the skeleton. Once the correspondence between markers is given, a transformation matrix, which represents the transformation from local coordinates to global coordinates, is calculated automatically by simulated annealing. The simulated annealing can decrease the sum of differences between the marker of the skeleton and the transformed marker of the local shape into global minimum. Result A rendered image of the reconstructed model of Kamegata-Ishi is shown in Figure 4(a). As the output model can be also represented in VRML2.0 format, the 3D image of the stone can be seen on the Internet http://chihara.aist-nara.ac.jp/people/99/masata-i/research02/kameishi.wrl. On the other hand, the information of surrounded environment is one of great cues for investigating the purpose of the stone. The authors also obtained the image of surrounded scenery from an omni directional camera and projected the reconstructed model with scenery onto a cylindrical immersive screen (diameter 6.0m, height 2.7m) at Nara Institute of Science and Technology. The projected image can bring the higher presence to observers (Figure 4(b)).
Figure 4: (a) Reconstructed model of Kamegata-Ishi (b) Projection on immersive display Discussion The heterogeneous measurement methods can measure a shape and a texture image of Kamegata-Ishi in a limited time and reconstruct a detailed 3D model by semi-automatic integration process. However, some problems still remain. First, search of markers is not fully automated. To make the search automatic, the authors consider that positions of measurement must be known. The knowledge of positions limits a range of searching for corresponding markers and the variation of color of markers enables identification of one-to-one correspondence. Secondly, change of lighting condition influences color tone of texture images. To solve this patching problem, the lighting condition must be made uniform during measurement, or color of a texture image must be adjusted gradually at the edge of the texture image in the way to match with the texture image of neighboring local shapes. Conclusion The authors archived Kamegata-Ishi (Turtle Shape Stone) digitally utilizing the data fusion from heterogeneous measurement methods, which are a total station, a non-contact 3D digitizer and a stereo camera. The heterogeneous measurement methods made it possible to reconstruct a detailed 3D shape and surface texture images of the entire stone. The semi-automatic registration between local models and a skeleton of an entire shape reduced sharply an amount of trials and errors in integration. Acknowledgements This research is in cooperation with Asuka Village (Nara, Japan) and Nara National Cultural Properties Research Institute. References
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