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- Institut für Computervisualistik (46) (remove)
Simulation of fractures
(2014)
Real-time computing often avoids the simulation of fractures due to its complexity. The field of engineering science provides methods to create these simulations to improve games and other applications. Steadily rising computer capacities allow suitable simulations on a real-time basis and make this aspect increasingly interesting. The topic and aim of this research is to simulate fractures of stiff bodies. The primary objective is the physical plausibility and performance of the application. This thesis analyses the potential of computer science to realize the simulation of fractures.
Three existing as well as one self-created were implemented and analysed. The works "Real time simulation of deformation and Fracture of stiff material" from Müller et al., "real time simulation of Brittle Fracture using Modal analysis" from Glondu et al. and "Fast and Controllable simulation of the Shattering of Brittle Objects" from Smith et al. form the basis of this thesis. The introduced methods use different computation of forces and fractures. The developed procedure uses the idea of generating secondary breaks. The approaches were implemented based on the Bullet physics-engine. The results of the work show that physically based breaks are realizable on a real-time basis.
The analysis of the physical methods demonstrates that their performance mainly depends on the constitution of the used objects. This thesis shows that the further investigation of this topic can discover new possibilities. The improvement of the realism in virtual worlds can be achieved by executing physically plausible methods.
In scientific data visualization huge amounts of data are generated, which implies the task of analyzing these in an efficient way. This includes the reliable detection of important parts and a low expenditure of time and effort. This is especially important for the big-sized seismic volume datasets, that are required for the exploration of oil and gas deposits. Since the generated data is complex and a manual analysis is very time-intensive, a semi-automatic approach could on one hand reduce the time required for the analysis and on the other hand offer more flexibility, than a fully automatic approach.
This master's thesis introduces an algorithm, which is capable of locating regions of interest in seismic volume data automatically by detecting anomalies in local histograms. Furthermore the results are visualized and a variety of tools for the exploration and interpretation of the detected regions are developed. The approach is evaluated by experiments with synthetic data and in interviews with domain experts on the basis of real-world data. Conclusively further improvements to integrate the algorithm into the seismic interpretation workflow are suggested.
In dieser Arbeit wird eine Unterrichtsreihe beschrieben, welche aus den drei Bereichen „mathematische Relationen“, „Datenbanken in Sozialen Netzwerken“ und „Datenschutz“ zusammengesetzt ist. Zu jedem Bereich wird ein eigener Unterrichtsentwurf präsentiert.
Außerdem wurde im Rahmen der vorliegenden Arbeit ein Programm zur Visualisierung der Relationen des Sozialen Netzwerks Instahub entworfen, welches im Anschluss an die Beschreibung der Unterrichtsreihe aufgeführt wird.
In order to plan the interior of a room, various programs for computers,
smart phones or head-mounted displays are available. The transfer to the
real environment is a difficult task. Therefore an augmented reality approach
is developed to illustrate the planning in the real room. If several
people want to contribute their ideas, conventional systems require to
work on one device together. The aim of this master thesis is to design and
develop a collaborative spatial planning application in augmented reality.
The application is developed in Unity with ARCore and C#.
Soziale Netzwerke spielen im Alltagsleben der Schülerinnen und Schüler eine entscheidende Rolle. Im Rahmen der vorliegenden Masterarbeit wurde ein Konzept für die Anzeige von Profilvorschlägen innerhalb des sozialen Netzwerks „InstaHub“, welches ein speziell für den Informatikunterricht programmiertes Werkzeug zum Thema „Datenbanken“ darstellt, entwickelt. Als Hürde stellte sich dabei dar, dass von den etablierten sozialen Netzwerken nur wenig bis gar keine Informationen über die Berechnung von Profil- oder Freundschaftsvorschlägen preisgegeben werden. Daher wurde zunächst das Wesen von Beziehungen zwischen Menschen in nicht-internetbasierten und in internetbasierten sozialen Netzwerken sowie die Gründe für Beziehungen zwischen Menschen in diesen Netzwerken dargelegt. Anhand der Beobachtung von Vorschlägen in anderen sozialen Netzwerken sowie der in InstaHub gespeicherten Nutzerdaten wurde ein Algorithmus für Profilvorschläge in InstaHub entworfen und mitsamt einer passenden Visualisierung entsprechend implementiert. Den zweiten Teil der Arbeit bildete eine Unterrichtseinheit für die Sekundarstufe II mit dem Thema Gefahren der Erzeugung und Verarbeitung von personenbezogenen Daten. In der Unterrichtseinheit dienen die Profilvorschläge in InstaHub, die auf von InstaHub über dessen Nutzer gesammelten Daten aufbauen, als Einstieg in die Thematik. Anschließend wird der Fokus von sozialen Netzwerken auf andere Online-Dienste erweitert und auf die Verarbeitung und Weitergabe dieser Daten eingegangen.
With the emergence of current generation head-mounted displays (HMDs), virtual reality (VR) is regaining much interest in the field of medical imaging and diagnosis. Room-scale exploration of CT or MRI data in virtual reality feels like an intuitive application. However in VR retaining a high frame rate is more critical than for conventional user interaction seated in front of a screen. There is strong scientific evidence suggesting that low frame rates and high latency have a strong influence on the appearance of cybersickness. This thesis explores two practical approaches to overcome the high computational cost of volume rendering for virtual reality. One lies within the exploitation of coherency properties of the especially costly stereoscopic rendering setup. The main contribution is the development and evaluation of a novel acceleration technique for stereoscopic GPU ray casting. Additionally, an asynchronous rendering approach is pursued to minimize the amount of latency in the system. A selection of image warping techniques has been implemented and evaluated methodically, assessing the applicability for VR volume rendering.
Das Ziel der vorliegenden Masterarbeit ist es, einen Einführungskurs in die Computervisualistik mit dem Schwerpunkt Computergrafik zu konzeptionieren und zu prototypisieren. Der Kurs sollte Grundlagen der Computergrafik vermitteln und dabei Bezüge zu anderen Veranstaltungen des Studiums herstellen, um Motivation und Verständnis für die komplexen Zusammenhänge der Studieninhalte in der Computervisualistik zu schaffen. Der aktuelle Studiengangplan weist hier bislang ein erkennbares Defizit auf. Für den Einführungskurs wurden prototypische Lerneinheiten auf Grundlage der didaktischen Methode der Moderation und unter Verwendung von Unity entwickelt. Konzept und Prototypen wurden an Probanden ohne informationstechnischen Hintergrund evaluiert. Die Ergebnisse zeigten, dass Unity eine geeignete Oberfläche für die Vermittlung der Informationen bietet. Diese stieß auf Akzeptanz und konnte leichte Zugänglichkeit bei den Probanden aufweisen, obwohl die Lerneinheiten selbst kleinere Schwächen aufwiesen. Im Anschluss an die erste Evaluationsphase wurde eine qualitative Umfrage mit Alumini der Computervisualistik durchgeführt. Die Ergebnisse bestätigten den Bedarf nach einer einführenden Veranstaltung zur Orientierung und zur Förderung von Motivation und Verständnis für die breiten Themengebiete der Computervisualistik.
In this thesis, we deal with the question if challenge, flow and fun in computer games are related to each other, and which influence the motivational, psychological components motivation of success, motivation of failure and the chance of success do have. In addition, we want to know if a free choice in the level of difficulty is the optimal way to flow. To examine these theories, a study based on an online survey was executed, in which the participants played the game “flOw“. The results were evaluated with the help of a two-factorial analysis of variance with repeated measurement and tests on correlation. Thereby we found out that there actually exists a relation between challenge, flow and fun and that motivation does matter indirectly.
This thesis presents a prototypical application for speech therapy as a therapeutical tool, simulating the articulation of German phonemes and the swallowing reflex. A special attention is given to a three-dimensional visualization of anatomical models of the pharyngolaryngeal region, which can be used in an interactive way. For examining the benefits of such an application in relation to conventional therapy mediums, the thesis considers iteratively the requirements of speech therapists.
One of the greatest goals in computer graphics is the aesthetic representation of objects. In addition to conventional methods, another field focuses on non-photorealistic renderings. The so-called example-based rendering is an area where users can transfer their art style to a pre-computed 3D rendering, using a hand-painted template. There are some algorithms that already provide impressive results, but their problem is that most of these procedures count as offline methods and are not able to produce results in real-time. For this reason, this work show a method that satisfies this condition. In addition, the influence of the run-time reduction on the results is investigated. Requirements are defined, to which the method and its results are examined. Other methods in this field are referenced and compared with their results.
Statistical Shape Models (SSMs) are one of the most successful tools in 3Dimage analysis and especially medical image segmentation. By modeling the variability of a population of training shapes, the statistical information inherent in such data are used for automatic interpretation of new images. However, building a high-quality SSM requires manually generated ground truth data from clinical experts. Unfortunately, the acquisition of such data is a time-consuming, error-prone and subjective process. Due to this effort, the majority of SSMs is often based on a limited set of this ground truth training data, which makes the models less statistically meaningful. On the other hand, image data itself is abundant in clinics from daily routine. In this work, methods for automatically constructing a reliable SSM without the need of manual image interpretation from experts are proposed. Thus, the training data is assumed to be the result of any segmentation algorithm or may originate from other sources, e.g. non-expert manual delineations. Depending on the algorithm, the output segmentations will contain errors to a higher or lower degree. In order to account for these errors, areas of low probability of being a boundary should be excluded from the training of the SSM. Therefore, the probabilities are estimated with the help of image-based approaches. By including many shape variations, the corrupted parts can be statistically reconstructed. Two approaches for reconstruction are proposed - an Imputation method and Weighted Robust Principal Component Analysis (WRPCA). This allows the inclusion of many data sets from clinical routine, covering a lot more variations of shape examples. To assess the quality of the models, which are robust against erroneous training shapes, an evaluation compares the generalization and specificity ability to a model build from ground truth data. The results show, that especially WRPCA is a powerful tool to handle corrupted parts and yields to reasonable models, which have a higher quality than the initial segmentations.
This work covers techniques for interactive and physically - based rendering of hair for computer generated imagery (CGI). To this end techniques
for the simulation and approximation of the interaction of light with hair are derived and presented. Furthermore it is described how hair, despite such computationally expensive algorithms, can be rendered interactively.
Techniques for computing the shadowing in hair as well as approaches to render hair as transparent geometry are also presented. A main focus of
this work is the DBK-Buffer, which was conceived, implemented and evaluated. Using the DBK-Buffer, it is possible to render thousands of hairs as
transparent geometry without being dependent on either the newest GPU hardware generation or a great amount of video memory. Moreover, a comprehensive evaluation of all the techniques described was conducted with respect to the visual quality, performance and memory requirements. This
revealed that hair can be rendered physically - based at interactive or even at real - time frame rates.
In current research of the autonomous mobile robots, path planning is still a very important issue.
This master's thesis deals with various path planning algorithms for the navigation of such mobile systems. This is not only to determine a collision-free trajectory from one point to another. The path should still be optimal and comply with all vehicle-given constraints. Especially the autonomous driving in an unknown and dynamic environment poses a major challenge, because a closed-loop control is necessary and thus a certain dynamic of the planner is demanded.
In this paper, two types of algorithms are presented. First, the path planner, based on A*, which is a common graph search algorithm: A*, Anytime Repairing A*, Lifelong Planning A*, D* Lite, Field D*, hybrid A*. Second, the algorithms which are based on the probabilistic planning algorithm Rapidly-exploring Random Tree (Rapidly-exploring Random Tree, RRT*, Lifelong Planning RRT*), as well as some extensions and heuristics. In addition, methods for collision avoidance and path smoothing are presented. Finally, these different algorithms are evaluated and compared with each other.
Today, augmented reality is becoming more and more important in several areas like industrial sectors, medicine, or tourism. This gain of importance can easily be explained by its powerful extension of real world content. Therefore, augmented realty became a way to explain and enhance the real world information. Yet, to create a system which can enhance a scene with additional information, the relation between the system and the real world must be known. In order to establish this relationship a commonly used method is optical tracking. The system calculates its relation to the real world from camera images. To do so, a reference which is known is needed in the scene to serve as an orientation. Today, this is mostly a 2D-marker or a 2D-texture. These are placed in the real world scenery to serve as a reference. But, this is an intrusion in the scene. That is why it is desirable that the system works without such an additional aid. An strategy without manipulating the scene is object-tracking. In this approach, any object from the scene can be used as a reference for the system. As an object is far more complex than a marker, it is harder for the system to establish its relationship with the real world. That is why most methods for 3D-object-tracking reduce the object by not using the whole object as reference. The focus of this thesis is to research how a whole object can be used as a reference in a way that either the system or the camera can be moved in any 360 degree angle around the object without loosing the relation to the real world. As a basis the augmented reality framework, the so called VisionLib, is used. Extensions to this system for 360 degree tracking are implemented in different ways and analyzed in the scope of this work. Also, the different extensions are compared. The best results were achieved by improving the reinitialization process. With this extension, current camera images of the scene are given to the system. With the hek of these images, the system can calculate the relation to the real world faster in case the relation went missing.
Die vorliegende Masterarbeit thematisiert die Evaluation einer sprachgesteuerten Lösung in der Produktion mit multimodaler Eingabe. Dabei wurden die Usability und die Benut-zerfreundlichkeit eines gewählten Sprachdialogsystems bewertet. Die Bewertung wurde mit Hilfe von Benutzertests und eines modifizierten SASSI-Fragebogens durchgeführt. Weiterhin wurden auch technische Kriterien, wie die Wortfehlerrate und die Out-of-grammar Rate zur Hilfe gezogen. Für den Versuch wurden zwei verschiedene Szenarien aus einer realen Produktionsum-gebung definiert. Dabei sollten die Teilnehmer verschiedene Aufgaben mit Hilfe des Testsystems erledigen. Die Interaktion mit dem Sprachdialogsystem fand anhand von ge-sprochenen Befehlen statt, welche durch eine Grammatik definiert wurden. Die Sprach-kommandos wurden durch die Zuhilfenahme eines WLAN-Headsets an das Sprachsys-tem übertragen. Während des Versuchs wurden Aussagen der Teilnehmer protokolliert und die technischen Kriterien notiert.
Das Ergebnis der Evaluation verdeutlicht, dass das Sprachdialogsystem eine hohe Quali-tät bezüglich Usability und Benutzerfreundlichkeit aufweist. Dabei sind die Wortfehler-rate und die Out-of-grammar Rate sehr niedrig ausgefallen und das System wurde von den Benutzern deutlich positiv bewertet. Nichtsdestotrotz wurden einige Kritikpunkte ge-nannt, die zu einer Verbesserung des Systems beitragen können.
Zusätzlich zum Rendern wird die Rechenleistung moderner Grafikkarten immer häufiger auch für allgemeine Berechnungen (GPGPU) genutzt. Für die Umsetzung stehen verschiedene Möglichkeiten zur Verfügung, die von der Verwendung der Renderingpipeline bis zu eigenständigen Schnittstellen reichen. In dieser Arbeit werden mit Render-To-Texture, Transform Feedback, Compute Shader und OpenCL vier verschiedene GPGPU-Methoden untersucht. Anhand von Partikelsystemen werden sie hinsichtlich der benötigten Berechnungszeit, der GPU-Auslastung, Lines of Code und Portierbarkeit miteinander verglichen. Dazu wurden sowohl das N-Körper Problem, Smoothed Particle Hydrodynamics und ein Partikelschwarm als Partikelsysteme umgesetzt. Es konnte gezeigt werden, dass insbesondere OpenCL und Compute Shader sehr gute Ergebnisse liefern.
One of the fundamental decisions during the development of any system is the representation of data. In computer graphics, objects are usually represented as sets of triangles. There are however many different variants with their own strengths and weaknesses. This thesis will explore distancefields as a representation for objects. Distancefields are functions, which map every point in space to the distance to the closest surface point. While this description is very simple, a number of interesting properties can be derived, allowing for a multitude of shapes, operations and effects. An overview of the necessary background and methods is given. Furthermore, some extended or new approaches are presented, such as displaying implicit surfaces, approximating indirect illumination or implementing a GPU tracer.
Im Bereich Augmented Reality ist es von großer Bedeutung, dass virtuelle
Objekte möglichst realistisch in ein Kamerabild eingebettet werden. Nur
so ist es möglich, dem Nutzer eine immersive Erfahrung zu bieten. Dazu
gehört unter anderem, Verdeckung dieser Objekte korrekt zu behandeln.
Während schon verschiedene Ansätze existieren, dieses Verdeckungsproblem
zu beheben, wird in dieser Arbeit eine Lösung mittels Natural Image
Matting vorgestellt. Mit Hilfe einer Tiefenkamera wird das Kamerabild in
Vorder- und Hintergrund aufgeteilt und anschließend das virtuelle Objekt
im Bild platziert. Für Bereiche, in denen die Zugehörigkeit zu Vorder- oder
Hintergrund nicht eindeutig ist, wird anhand bekannter Pixel ein Transparenz-
Wert geschätzt. Es werden Methoden präsentiert, welche einen
Ablauf des Image Matting in Echtzeit ermöglichen. Zudem werden
Verbesserungsmöglichkeiten dieser Methoden präsentiert und gezeigt, dass
durch diese eine höhere Bildqualität für schwierige Szenen erreicht wird.
Einfluss eines Ausrichtungswerkzeugs auf die Bedienbarkeit in unbeaufsichtigten Eyetrackingsystemen
(2015)
Eye gaze trackers are devices that can estimate the direction of gaze of a person. Among usability testing eye tracking also allows persons with decreased limb mobility to control or to interact with the computer. The quality and availability of eye tracking equipment has been increasing while costs have been decreasing. This development leads to entering new markets by using eye tracking as an additional input dimension for a variety of applications. Up to now eye tracking has been supervised by qualified experts, who assured that the important conditions like position in front of the eye tracking device, calibration and light conditions has been kept, while using.
This thesis examines an adjustment tool, which is helping the user to adjust in front of the eye tracker and helping to keep this position during the experiment. Furthermore the accuracy while moving the head has been analysed. In this experiment an remote eye gaze tracker has been used to control a game character in the video game called 'Schau Genau!'. The goal was to determine whether the game is playable without the barrier of adjusting and calibration. The results show that adjusting in front of an eye tracker is not a problem, keeping this position is. Small changes of the head position after the calibration process leads to a lack of accuracy. Giving up the calibration and using someone else calibration shows way bigger deviation. Additional head movement increases error rate and makes controlling more difficult.
The goal of simulations in computergraphics is the simulation of realistic phenomena of materials. Therefore, internal and external acting forces are accumulated in each timestep. From those, new velocities get calculated that ultimately change the positions of geometry or particles. Position Based Dynamics omits thie velocity layer and directly works on the positions. Constraints are a set of rules defining the simulated material. Those rules must not be violated throughout the simulation. If this happens, the violating positions get changed so that the constraints get fullfilled once again. In this work a PBD-framework gets implemented, that allows simulations of solids and fluids. Constraints get solved using GPU implementations of Gauss-Seidel and Gauss-Jakobi solvers. Results are physically plausible simulations that are real-time capable.