Template based shape processing

As computers can only represent and process discrete data, information gathered from the real world always has to be sampled. While it is nowadays possible to sample many signals accurately and thus generate high-quality reconstructions (for example of images and audio data), accurately and densely sampling 3D geometry is still a challenge. The signal samples may be corrupted by noise and outliers, and contain large holes due to occlusions. These issues become even more pronounced when also considering the temporal domain. Because of this, developing methods for accurate reconstruction of shapes from a sparse set of discrete data is an important aspect of the computer graphics processing pipeline. In this thesis we propose novel approaches to including semantic knowledge into reconstruction processes using template based shape processing. We formulate shape reconstruction as a deformable template fitting process, where we try to fit a given template model to the sampled data. This approach allows us to present novel solutions to several fundamental problems in the area of shape reconstruction. We address static problems like constrained texture mapping and semantically meaningful hole-filling in surface reconstruction from 3D scans, temporal problems such as mesh based performance capture, and finally dynamic problems like the estimation of physically based material parameters of animated templates.Analoge Signale müssen digitalisiert werden um sie auf modernen Computern speichern und verarbeiten zu können. Für viele Signale, wie zum Beispiel Bilder oder Tondaten, existieren heutzutage effektive und effiziente Digitalisierungstechniken. Aus den so gewonnenen Daten können die ursprünglichen Signale hinreichend akkurat wiederhergestellt werden. Im Gegensatz dazu stellt das präzise und effiziente Digitalisieren und Rekonstruieren von 3D- oder gar 4D-Geometrie immer noch eine Herausforderung dar. So führen Verdeckungen und Fehler während der Digitalisierung zu Löchern und verrauschten Meßdaten. Die Erforschung von akkuraten Rekonstruktionsmethoden für diese groben digitalen Daten ist daher ein entscheidender Schritt in der Entwicklung moderner Verarbeitungsmethoden in der Computergrafik. In dieser Dissertation wird veranschaulicht, wie deformierbare geometrische Modelle als Vorlage genutzt werden können, um semantische Informationen in die robuste Rekonstruktion von 3D- und 4D Geometrie einfließen zu lassen. Dadurch wird es möglich, neue Lösungsansätze für mehrere grundlegenden Probleme der Computergrafik zu entwickeln. So können mit dieser Technik Löcher in digitalisierten 3D Modellen semantisch sinnvoll aufgefüllt, oder detailgetreue virtuelle Kopien von Darstellern und ihrer dynamischen Kleidung zu erzeugt werden

Performance evaluation of closed-loop logistics systems with generally distributed service times

The performance evaluation of hospital logistics is becoming more and more important to guarantee efficient services in health establishments. Therefore, we propose a new discrete-time approach for the steady-state analysis of closed-loop queueing systems with arbitrary topology and generally distributed service times. Based on a finite Markov chain, it is possible to compute the complete cycle time distribution of service systems with a population constraint. In addition, the distribution of the number of customers at each service station can be obtained. The method is applied to the analysis of a sterilization process of medical devices. To verify the method, we compare the results of our discrete-time approach to the results that are obtained by a simulation model

PatchNets: Patch-Based Generalizable Deep Implicit 3D Shape Representations

Implicit surface representations, such as signed-distance functions, combined with deep learning have led to impressive models which can represent detailed shapes of objects with arbitrary topology. Since a continuous function is learned, the reconstructions can also be extracted at any arbitrary resolution. However, large datasets such as ShapeNet are required to train such models. In this paper, we present a new mid-level patch-based surface representation. At the level of patches, objects across different categories share similarities, which leads to more generalizable models. We then introduce a novel method to learn this patch-based representation in a canonical space, such that it is as object-agnostic as possible. We show that our representation trained on one category of objects from ShapeNet can also well represent detailed shapes from any other category. In addition, it can be trained using much fewer shapes, compared to existing approaches. We show several applications of our new representation, including shape interpolation and partial point cloud completion. Due to explicit control over positions, orientations and scales of patches, our representation is also more controllable compared to object-level representations, which enables us to deform encoded shapes non-rigidly.Comment: 25 pages, including supplementary material. Code: https://github.com/edgar-tr/patchnets Project page: https://gvv.mpi-inf.mpg.de/projects/PatchNets

Preconditioning for a Phase-Field Model with Application to Morphology Evolution in Organic Semiconductors

The Cahn--Hilliard equations are a versatile model for describing the evolution of complex morphologies. In this paper we present a computational pipeline for the numerical solution of a ternary phase-field model for describing the nanomorphology of donor--acceptor semiconductor blends used in organic photovoltaic devices. The model consists of two coupled fourth-order partial differential equations that are discretized using a finite element approach. In order to solve the resulting large-scale linear systems efficiently, we propose a preconditioning strategy that is based on efficient approximations of the Schur-complement of a saddle point system. We show that this approach performs robustly with respect to variations in the discretization parameters. Finally, we outline that the computed morphologies can be used for the computation of charge generation, recombination, and transport in organic solar cells

Ground verification of the feasibility of telepresent on-orbit servicing

In an ideal case telepresence achieves a state in which a human operator can no longer differentiate between an interaction with a real environment and a technical mediated one. This state is called transparent telepresence. The applicability of telepresence to on-orbit servicing (OOS), i.e., an unmanned servicing operation in space, teleoperated from ground in real time, is verified in this paper. For this purpose, a communication test environment was set up on the ground, which involved the Institute of Astronautics (LRT) ground station in Garching, Germany, and the European Space Agency (ESA) ground station in Redu, Belgium. Both were connected via the geostationary ESA data relay satellite ARTEMIS. Utilizing the data relay satellite, a teleoperation was accomplished in which the human operator as well as the (space) teleoperator was located on the ground. The feasibility of telepresent OOS was evaluated, using an OOS test bed at the Institute of Mechatronics and Robotics at the German Aerospace Center (DLR). The manipulation task was representative for OOS and supported real-time feedback from the haptic-visual workspace. The tests showed that complex manipulation tasks can be fulfilled by utilizing geostationary data relay satellites. For verifying the feasibility of telepresent OOS, different evaluation methods were used. The properties of the space link were measured and related to subjective perceptions of participants, who had to fulfill manipulation tasks. An evaluation of the transparency of the system, including the data relay satellite, was accomplished as well

The MASCOT Magnetometer

The Mobile Asteroid Scout (MASCOT) is a small lander on board the Hayabusa2 mission of the Japan Aerospace Exploration Agency to the asteroid 162173 Ryugu. Among the instruments on MASCOT is a fluxgate magnetometer, the MASCOT Magnetometer (MasMag). The magnetometer is a lightweight ( ∼280 g∼280 g ) and low power ( ∼0.5 W∼0.5 W ) triaxial fluxgate magnetometer. Magnetic field measurements during the landing period and during the surface operational phase shall provide information about any intrinsic magnetic field of the asteroid and its remanent magnetization. This could provide important constraints on planet formation and the thermal and aqueous evolution of primitive asteroids.Thomas F. PetersonUnited States. National Aeronautics and Space Administration. Emerging Worlds Progra

Survey of the Current Activities in the Field of Modeling the Space Debris Environment at TU Braunschweig

The Institute of Space Systems at Technische Universität Braunschweig has long-term experience in the field of space debris modeling. This article reviews the current state of ongoing research in this area. Extensive activities are currently underway to update the European space debris model MASTER. In addition to updating the historical population, the future evolution of the space debris environment is also being investigated. The competencies developed within these activities are used to address current problems with regard to the possibility of an increasing number of catastrophic collisions. Related research areas include, for example, research in the field of orbit determination and the simulation of sensor systems for the acquisition and cataloging of orbital objects. In particular, the ability to provide simulated measurement data for object populations in almost all size ranges is an important prerequisite for these investigations. Some selected results on the distribution of space debris on Earth orbit are presented in terms of spatial density. Furthermore, specific fragmentation events will be discussed

TRPM7 Kinase Controls Calcium Responses in Arterial Thrombosis and Stroke in Mice

Objective: TRPM7 (transient receptor potential cation channel, subfamily M, member 7) is a ubiquitously expressed bifunctional protein comprising a transient receptor potential channel segment linked to a cytosolic alpha-type serine/threonine protein kinase domain. TRPM7 forms a constitutively active Mg2+ and Ca2+ permeable channel, which regulates diverse cellular processes in both healthy and diseased conditions, but the physiological role of TRPM7 kinase remains largely unknown. Approach and Results: Here we show that point mutation in TRPM7 kinase domain deleting the kinase activity in mice (Trpm7(R/R)) causes a marked signaling defect in platelets. Trpm7(R/R) platelets showed an impaired PIP2 (phosphatidylinositol-4,5-bisphosphate) metabolism and consequently reduced Ca2+ mobilization in response to stimulation of the major platelet receptors GPVI (glycoprotein VI), CLEC-2 (C-type lectin-like receptor), and PAR (protease-activated receptor). Altered phosphorylation of Syk (spleen tyrosine kinase) and phospholipase C gamma 2 and beta 3 accounted for these global platelet activation defects. In addition, direct activation of STIM1 (stromal interaction molecule 1) with thapsigargin revealed a defective store-operated Ca2+ entry mechanism in the mutant platelets. These defects translated into an impaired platelet aggregate formation under flow and protection of the mice from arterial thrombosis and ischemic stroke in vivo. Conclusions: Our results identify TRPM7 kinase as a key modulator of phospholipase C signaling and store-operated Ca2+ entry in platelets. The protection of Trpm7(R/R) mice from acute ischemic disease without developing intracranial hemorrhage indicates that TRPM7 kinase might be a promising antithrombotic target