Reconstruction and rendering of time-varying natural phenomena

While computer performance increases and computer generated images get ever more realistic, the need for modeling computer graphics content is becoming stronger. To achieve photo-realism detailed scenes have to be modeled often with a significant amount of manual labour. Interdisciplinary research combining the fields of Computer Graphics, Computer Vision and Scientific Computing has led to the development of (semi-)automatic modeling tools freeing the user of labour-intensive modeling tasks. The modeling of animated content is especially challenging. Realistic motion is necessary to convince the audience of computer games, movies with mixed reality content and augmented reality applications. The goal of this thesis is to investigate automated modeling techniques for time-varying natural phenomena. The results of the presented methods are animated, three-dimensional computer models of fire, smoke and fluid flows.Durch die steigende Rechenkapazität moderner Computer besteht die Möglichkeit immer realistischere Bilder virtuell zu erzeugen. Dadurch entsteht ein größerer Bedarf an Modellierungsarbeit um die nötigen Objekte virtuell zu beschreiben. Um photorealistische Bilder erzeugen zu können müssen sehr detaillierte Szenen, oft in mühsamer Handarbeit, modelliert werden. Ein interdisziplinärer Forschungszweig, der Computergrafik, Bildverarbeitung und Wissenschaftliches Rechnen verbindet, hat in den letzten Jahren die Entwicklung von (semi-)automatischen Methoden zur Modellierung von Computergrafikinhalten vorangetrieben. Die Modellierung dynamischer Inhalte ist dabei eine besonders anspruchsvolle Aufgabe, da realistische Bewegungsabläufe sehr wichtig für eine überzeugende Darstellung von Computergrafikinhalten in Filmen, Computerspielen oder Augmented-Reality Anwendungen sind. Das Ziel dieser Arbeit ist es automatische Modellierungsmethoden für dynamische Naturerscheinungen wie Wasserfluss, Feuer, Rauch und die Bewegung erhitzter Luft zu entwickeln. Das Resultat der entwickelten Methoden sind dabei dynamische, dreidimensionale Computergrafikmodelle

Hybrid Homographies and Fundamental Matrices Mixing Uncalibrated Omnidirectional and Conventional Cameras

International audienceIn this paper, we present a deep analysis of the hybrid two-view relations combining images acquired with uncalibrated central catadioptric systems and conventional cameras. We consider both, hybrid fundamental matrices and hybrid planar homographies. These matrices contain useful geometric information. We study three different types of matrices, varying in complexity depending on their capacity to deal with a single or multiple types of central catadioptric systems. The first and simplest one is designed to deal with para-catadioptric systems, the second one and more complex considers the combination of a perspective camera and any central catadioptric system. The last one is the complete and generic model which is able to deal with any combination of central catadioptric systems. We show that the generic and most complex model sometimes is not the best option when we deal with real images. Simpler models are not as accurate as the complete model in the ideal case, but they provide a better and more accurate behavior in the presence of noise, being simpler and requiring less correspondences to be computed. Experiments with simulated data and real images are performed. To show the potential of these approaches, we develop two applications. The first is the successful matching between perspective images and hyper-catadioptric images using SIFT descriptors. In the second one, using only the hybrid fundamental matrix and the hybrid planar homography we compute the metric localization of the perspective camera inside the catadioptric view in an indoors environment

Plenoptische Modellierung und Darstellung komplexer starrer Szenen

Image-Based Rendering is the task of generating novel views from existing images. In this thesis different new methods to solve this problem are presented. These methods are designed to fulfil special goals such as scalability and interactive rendering performance. First, the theory of the Plenoptic Function is introduced as the mathematical foundation of image formation. Then a new taxonomy is introduced to categorise existing methods and an extensive overview of known approaches is given. This is followed by a detailed analysis of the design goals and the requirements with regards to input data. It is concluded that for perspectively correct image generation from sparse spatial sampling geometry information about the scene is necessary. This leads to the design of three different Image-Based Rendering methods. The rendering results are analysed on different data sets. For this analysis, error metrics are defined to evaluate different aspects