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Modelling Archaeological Collections Equipment The main RP source at IITK is a Fused Deposition Modeling system (FDM) RP system [5] at Computer Aided Design Lab (CAD Lab) a central facility of the institution. The system is Stratasys FDM 1650, equipped for prototyping with ABS plastic. For data acquisition for RE at CAD Lab, a ATOS II optical scanner [6] is used. The main computer facility for RP at CAD Lab are two Silicon Graphics on Irix platform, several PC with 512 MB RAM and 40 GB local disks.  Fig. 3. The RP model Case Study A digitising exercise of a Hanuman idol carved from a rock slab was taken up. An ATOS II optical scanner was used to digitize the sculpture. Optical scanners have a high rate of digitizing and are non-contact and these are the essential advantages of using them for scanning large stone monuments. Fig. 1 shows the idol chosen for scanning. The idol’s gross dimensions are ~ 1 ¼ ft X 2 ½ ft X ½ ft. The time taken to scan the idol was approximately an hour. The point cloud was then sampled based on curvature to approximately 1,30000 points. The point density has to be fixed according to the size of the object and the intricacy of features. The point data was then processed to yield connectivity list file that described the relationship of the points to each other. The output of the processing is a STL file that consists of a list of triangular facet data. The time to process the data was 25 minutes on a PIII, 1GB RAM UNIX Workstation. The critical issue here is the requirement of computers with high-speed processing and large memory for real time handling of huge point cloud data. The point cloud and the STL file of the Hanuman idol are shown in Fig. 2. The digital model thus created can be used for viewing, dimensional and mass property evaluation and surface feature analysis to name a few. Reproduction of the artifact from its digital representation through RP or conventional CNC machining is readily feasible. The STL file of the Hanuman idol was used to reconstruct the same through the FDM RP system in the Lab. A half-size scaled model was fabricated. The fabricated physical model is shown in Fig. 3. The model of the artifact made by RP presents a new effort in bringing information-based manufacturing technology for archaeological studies. The accuracy and reproducibility of the models provide archaeologists and scientists with a better way to preserve artifacts and a more durable, yet tangible subject to study. A complete archaeological monument could be scanned and a digital model created. This model can be placed on to 3D Digital Terrain Model (DTM) obtained form satellite imaging to yield a detailed 3D model of the archaeological site along with monuments. The work on these lines is in progress at our lab. Reverse Engineering of physical objects to obtain three-dimensional geometrical models and physical realization of these models through rapid prototyping is a fast developing technology in which interest is currently high. The present study has demonstrated the application of data acquisition through RE and form realisation through RP for modeling archaeological collections. India is bestowed with many instances of human creation from various ages in the form of temple monuments and other artifacts. Though these forms of art have survived test of the time but many have been destroyed by natural calamities or man-made disasters in the form of war and terrorism. The authors hope that the present study will pave a way towards digital preservation of these invaluable and unique artifacts. References
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