Optical motion capturing explains the three-Dimensional (3D) position estimation of points through triangulation employing several depth cameras. Prosperous performance relies on level of visibility of points from different cameras and the overlap of captured meshes in-between. Generally, the accuracy of the estimation is practically based on the camera parameters e.g., location and orientations. Accordingly, the camera network configurations play a key role in the quality of the estimated mesh. This paper proposes an optimal approach for camera placement based on characteristics of a depth camera D435i - Intel RealSense. The optimal problem includes a cost function that contains several minimisation and maximisation terms. The minimisation terms are distance of the cameras to the center of the scanning object, resolution error, and sparsity. And the maximisation terms are distance between each two pair of cameras, percent of captured point from an object, and the level of overlap between cameras. The object is designed based on practical experiments of human walking and is a bounding box around one step of dynamic foot work-space from heel strike posture to toe-off posture. The accuracy and robustness of the algorithms are assessed via experiment measurement, and sensitivity to the number of cameras is investigated. Accordingly, the experiment results determined that the scanning accuracy can be as high as 2.5 % based on a reference scan with a high-end scanner (Artec Eva).

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Fitting apparel and apparel in performing different activities is essential for the functional yet comfortable experience of the user. 4D scans, i.e. 3D scans in continuous timestamps, of the body (part) in performing those activities are the basis for the design of garments/apparel in 4D. In this paper, we proposed a semi-automatic workflow for constructing 4D scans of the body parts with the emphasis on registering noisy scans at a given timestamp. Continuous 3D scans regarding the moving body parts are captured first from different depth cameras from different view angles. In a given timestamp, the collected 3D scans are roughly aligned to a template using the rigid Iterative Closest Points (ICP) algorithm. Then these scans are further registered using a newly proposed non-rigid Iterative Closest-Farthest Points (ICFP) algorithm, in which correspondences between the source and the target are established by either closest or farthest points based on the newly defined logical distance concept and the probability theory. Experimental results indicated that the ICFP method is robust against noise and the scanning accuracy can be as high as 3.4 %. It also reveals that, for the human foot, the differences of ball width and ball angles between the loaded and the unloaded situation can be as large as 8 mm and 2 degrees, respectively. This highlights the importance of using 4D scan in designing garments and apparel.

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This thesis describes the design and development of an accurate and low cost 4D foot scanner in the context of podiatry. The intention is to make a first step towards the development of an affordable 4D foot scanner with commercial grade performance at a low cost, using commodity hardware. By doing so, 4D scanning can hopefully become more accessible to the general public, and accelerate the development and adoption of ultra personalized footwear and digital manufacturing in healthcare. Podiatrists focus on the treatment of physical conditions in the lower regions of the human body, which are often related to foot conditions. Personalized footwear solutions (e.g. orthotics) are widely used to relieve a patient of such conditions, which are primarily designed based on static 3D scanning data of the foot. With additional input of motion analyses and professional experience, a podiatrist can adjust the design of an orthotic to fit the patient. However, the change in foot measurements during different phases of the gait cycle are not accounted for in the design of these personalized solutions, which could vary up to 8 mm. With 4D foot scanning (dynamic 3D scanning), podiatrists will be able to observe and acquire data of the dynamic morphology of a foot during the gait cycle. This should allow the design and development of truly personalized orthotics that are able to support a patient during the entire gait cycle. To support this vision, a proof of concept of a 4D foot scanner has been developed. The presented proof of concept iterates over a previously built 4D foot scanner (Vidmar, 2020). The proof of concept includes: an optimized embodiment for improved scanning quality and scanning consistency, a trigger system to improve the human-computer interaction of the scanner, and a scalable camera configuration for up to 9 cameras. The hardware performance of the scanner in combination with the newly designed data acquisition pipeline has been evaluated in terms of acquisition consistency, speed, and memory usage. The outcome is that the scanner is able to manage dynamic data acquisition with a camera configuration of 9. Also, for a camera configuration of 7, the scanner shows a linear trend in memory consumption, acquired frames, and acquisition speeds, which suggests that performance of the scanner is predictable and constant for this configuration. More elaborate analyses should give better insights into the long time performance of the scanner for different camera configurations. The evaluation of the quality of both static and dynamic scanning data has been done with the implementation of nonrigid ICP. The accuracy of the scanner showed a minimal accuracy error of 2.274 mm. Compared with international 3D scanning standards (minimum accuracy error of 2 mm), the performance of the scanner is considered as a desirable outcome for this graduation project.