Investigation on methods for making detailed digital models of sculptures and other artefacts
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Sculptures and other artifacts are exposed on damages and it is hard to avoid them. For cultural heritage preservation new replicas of these objects should be done. For this purpose the best solution is to use non-touching methods, like photogrammetry and three-dimensional scanning, which will not do any harm to the object. Afterwards 3D digital model may be used and by applying of 3D printers the real copy may be done. The purpose of the report was to investigate methods on making detailed digital models on example of a sculpture from Nidaros Cathedral. The goal was to get as accurate – detailed model as possible. There is comparison on photogrammetric, 3D scanning methods and available 3D modelling tools. To make very detailed digital model of round, complex, and small objects – very big point cloud is needed. The point cloud has to be accurate with high resolution. To make such a point cloud from images any software needs a lot of time for computation. Also the data from scanning – if the point clouds include big amount of points – the time of computation also takes a lot of time. This is not because of low PC, but because of software limitations. Some scanners are able to make more dense point cloud with better accuracy as others. With higher resolution and better accuracy scanners become smaller, and also distance range is decreasing. Though, for small object it is required. Photogrammetry may produce also very good results, if only the material is non-reflective/shiny, or a glass. In the project photogrammetric software has been used, such as PhotoModeler Scanner and Topcon ImageMaster, where both are able to create 3D surface from photographs, taken by non-metric camera. Both softwares provide camera calibration. The results at the end were quite good, but the sculpture is quite shiny and reflects the light, and this situation is not required for image matching and creating 3D points. Therefore, the model results with a lot of noise. Also, the time needed for DSM creating was very long and this part still needs some improvement. Free software from Autodesk – Project Photofly 2.0 was also tested. The application creates mesh and may be used by non-experienced users. Nevertheless, the results are not so accurate or the resolution is lower, it still may be used in most common situations. From laser scanning, Konica Minolta VI-910 was used for data acquisition, but also very interesting hand held small scanner from Artec was used. Both are created for small range distances; nevertheless Artec seems to be better for smaller objects. It has better accuracy and higher resolution. In both cases, softwares recommended by the companies were used for modelling. Geomagic software was also used for post processing afterwards. Polygon EditingTool from Konica Minolta seemed not working properly with new Windows 7 x64 bits, but Artec was even able to use most of the processors cores for computations. The best model was achieved by applying small structured scanner from Artec with 0,5mm ofresolution and accuracy up to 0,1mm. The model created using Artec software works good, but in the author’s opinion Geomagic software works better, where smoothing may be done inthe respect to curves.