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Reconstructing 3D face shape from a single 2D photograph as well as from video is an inherently ill-posed problem with many ambiguities. One way to solve some of the ambiguities is using a 3D face model to aid the task. 3D morphable face models (3DMMs) are amongst the state of the art methods for 3D face reconstruction, or so called 3D model fitting. However, current existing methods have severe limitations, and most of them have not been trialled on in-the-wild data. Current analysis-by- synthesis methods form complex non linear optimisation processes, and optimisers often get stuck in local optima. Further, most existing methods are slow, requiring in the order of minutes to process one photograph.
This thesis presents an algorithm to reconstruct 3D face shape from a single image as well as from sets of images or video frames in real-time. We introduce a solution for linear fitting of a PCA shape identity model and expression blendshapes to 2D facial landmarks. To improve the accuracy of the shape, a fast face contour fitting algorithm is introduced. These different components of the algorithm are run in iteration, resulting in a fast, linear shape-to- landmarks fitting algorithm. The algorithm, specifically designed to fit to landmarks obtained from in-the-wild images, by tackling imaging conditions that occur in in-the-wild images like facial expressions and the mismatch of 2D–3D contour correspondences, achieves the shape reconstruction accuracy of much more complex, nonlinear state of the art methods, while being multiple orders of magnitudes faster.
Second, we address the problem of fitting to sets of multiple images of the same person, as well as monocular video sequences. We extend the proposed shape-to-landmarks fitting to multiple frames by using the knowledge that all images are from the same identity. To recover facial texture, the approach uses texture from the original images, instead of employing the often-used PCA albedo model of a 3DMM. We employ an algorithm that merges texture from multiple frames in real-time based on a weighting of each triangle of the reconstructed shape mesh.
Last, we make the proposed real-time 3D morphable face model fitting algorithm available as open-source software. In contrast to ubiquitous available 2D-based face models and code, there is a general lack of software for 3D morphable face model fitting, hindering a widespread adoption. The library thus constitutes a significant contribution to the community.
Within the scope of the present cumulative doctoral thesis six scientific papers were published which illustrates that modern reaction model-free (=isoconversional) kinetic analysis (ICKA) methods represents a universal and effective tool for the controlled processing of thermosetting materials. In order to demonstrate the universal applicability of ICKA methods, the thermal cure of different thermosetting materials having a very broad range of chemical composition (melamine-formaldehyde resins, epoxy resins, polyester-epoxy resins, and acrylate/epoxy resins) were analyzed and mathematically modelled. Some of the materials were based on renewable resources (an epoxy resin was made from hempseed oil; linseed oil was modified into an acrylate/epoxy resin). With the aid of ICKA methods not only single-step but also complex multi-step reactions were modelled precisely. The analyzed thermosetting materials were combined with wood, wood-based products, paper, and plant fibers which are processed to various final products. Some of the thermosetting materials were applied as coating (in form of impregnated décor papers or powder and wet coatings respectively) on wood substrates and the epoxy resin from hempseed oil was mixed with plant fibers and processed into bio-based composites for lightweight applications. From the final products mechanical, thermal, and surface properties were determined. The activation energy as function of cure conversion derived from ICKA methods was utilized to predict accurately the thermal curing over the course of time for arbitrary cure conditions. Furthermore the cure models were used to establish correlations between the cross-linking during processing into products and the properties of the final products. Therewith it was possible to derive the process time and temperature that guarantee optimal cross-linking as well as optimal product properties