Kaufman, John and Rennie, Allan (2018) Replication and fabrication of crafted and natural artifacts by reverse engineering using single camera photogrammetry. PhD thesis, Lancaster University.
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Abstract
Photogrammetry has been used for recording objects for well over one hundred and fifty years. Modern photogrammetry, or digital image capture, can be used with the aid of a single medium range Digital Single Lens Reflex (DSLR) camera, to transform two-dimensional (2D) images into three-dimensional (3D) Computer Aided Design (CAD) spatial representations, and together with the use of additive manufacturing (AM) or 3D Printing technology, geometric representations of original cultural, historic and geological artifacts can be fabricated using a process known as Non-invasive Reverse Engineering. Being able to replicate such objects is of great benefit to educationalists and, for example, curators; if the original object cannot be handled because it is fragile, then replicas can give the handler a chance to experience the size, texture and weight of rare objects. Photogrammetry equipment is discussed, the objective being simplicity of execution for eventual realisation of physical products such as the artifacts discussed in this thesis. All the digital photographic data in the research has been captured either with the use of a mid-range DSLR camera or a compact “point and shoot” camera. As the processing power of computers has increased and become more widely available, and with the use of user-friendly software programs it is now possible to digitally combine multi-view photographs, taken from 360° around the object, into 3D CAD representational virtual images, transforming these so they are ready for AM machines to produce replicated models of the originals. Over 50 objects were used in this research and the results documented: from the reproduction of small modern clay sculptures; 3,500-year-old Egyptian artifacts; household vases, figurines and bottles; fossils, shells and rocks, although not all successfully recreated. A variety of AM technologies have been employed, mostly monochromatic but including colour AM machines, to fabricate the models where good 3D models have been obtained. A bench-mark test was performed to ascertain the justification for the additional time and computer power required to produce ultra-high resolution digital images for the models to be fabricated on high resolution AM technology, in order to test the best possible limits of artifact reproduction. An in-depth case study on four problematic artifacts was also conducted using amongst other methods, RAW photographic images as opposed to camera ready Jpeg images; the results were analysed for comparison and conclusions were drawn.