Talks - Computer Graphics Lab

April 13, 2012 13:00 Informatikzentrum, Seminarraum G30	Promotions-vor-vortrag Albuquerque Georgia Albuquerque Promotions-vor-vortrag Georgia Albuquerque
March 26, 2012 13:00 Informatikzentrum, Seminarraum G30	Promotions-vor-vortrag Lipski Christian Lipski Promotions-vor-vortrag christian Lipski
March 19, 2012 13:00 Informatikzentrum, Seminarraum G30	MA-Vortrag "Folding Textures" Thorben Schulze Texturen werden seid bereits mehr als 30 Jahren in der Computergraphik verwendet um Modellkomplexität vorzutäuschen, welche nicht in der Geometrie selbst widergespiegelt wird. Dabei werden zumeist statische Texturkoordinaten an die Eckpunkte eines Modells zugewiesen, welche während der Bildsynthese interpoliert und dann zum Nachschlagen in der Texturkarte verwendet werden. Zwar bieten heutige Graphik-APIs rudimentäre Möglichkeiten diese Koordinaten zu verändern, doch ist dies im Grunde beschränkt auf einfache Transformationen, welche sich mittels einer Homographie beschreiben lassen. Komplexere Funktionen werden nicht unterstützt. Ziel dieser Arbeit ist es die Transformation der Zuweisung von Texturkoordinaten auf einem Dreiecksmodell zu verallgemeinern, um auf diese Weise komplexere Effekte darstellen zu können, dazu gehört im einfachsten Falle beliebige Transformationsfunktionen anzuwenden, aber auch komplexere Abläufe, wie Sprünge in der Textur zu erlauben, oder übereinander gefaltete Texturen zu erzeugen. Damit wäre es beispielsweise möglich Effekte zu erzeugen, wie etwa sich überlagernde Schuppen, die sich der Bewegung des Modells anpassen, Dehnungsvisualisierungen, Wassereffekte über einem beliebigen Untergrund und das alles ohne die Geometrie selbst zu verändern.
March 5, 2012 13:00 Informatikzentrum, Seminarraum G30	BA-Vortrag The capturing of turbulent gas ﬂows using Kinect Mark Albers Vortrag über die Bachelorarbeit "The capturing of turbulent gas ﬂows using Kinect" - die Tiefenkarten mehrerer Kinects werden ausgewertet und minimale Änderungen induziert durch ein Gas, welches von allen Kinects erfasst wird, werden zur Rekonstruktion desselben verwendet.
February 27, 2012 13:00 Informatikzentrum, Seminarraum G30	Promotions-vor-vortrag Berger Kai Berger In this talk i lay out the parts of my thesis, that is modeling and verification of light-matter interaction phenomena. The first part focuses on a new setup for capturing and modeling immersed surface reflectances, while the second part introduces ellipsometry as a new way verify the real-world applicability of existing reflectance models, which are widely considered physically plausible.
February 6, 2012 13:00 Informatikzentrum, Seminarraum G30	MA-Vortrag Inverse erweiterte Realität auf einem Mobiltelefon Martin Fiebig Bei normaler erweiterter Realität (Augmented Reality) wird ein Kamerabild um Informationen erweitert. Diese Informationen werden aufgrund von Sensorendaten dem Kamerabild angepasst. Auf einem Smartphone können dies z. B. ein GPS-Signal, Kompassdaten, Gyroskopdaten oder eine beliebige Kombination aus diesen Daten sein. Auch ausgedruckte Marker oder QR-Codes können verwendet werden, um die Lage der Kamera zu bestimmen oder Bereiche im Kamerabild zu identifizieren. Bei der inversen erweiterten Realität wird eine virtuelle Umgebung erschaffen und mit realen Inhalten ergänzt. Die realen Inhalte sollen in diesem Fall von der Kamera stammen. Eine vor die Videokamera getretene Person soll vom Hintergrund getrennt und in eine virtuelle Szene eingefügt werden.
January 23, 2012 13:00 Informatikzentrum, Seminarraum G30	BA-Vortrag "Plug-in-based Rapid Prototype Development Tool" Timo Veit Eine Reihe von aktuellen Grafikalgorithmen nutzen Fotos, Videos oder Bilddatenbanken als Eingabe. Eine vereinheitlichte Schnittstelle und intuitive Benutzeroberfläche zur Verarbeitung dieser Daten könnte dabei von großem Nutzen sein, um die Entwicklung neuer Algorithmen zu beschleunigen, sowie bereits bestehende zu integrieren. Ein solches Framework benötigt dabei eine Reihe von Funktionalitäten, wie bspw. das Laden, Speichern, Anzeigen von Bildern oder Videoframes, Scribble Funktionalität, Streaming, graphenbasierter Datenfluss, und vieles mehr. In dieser Arbeit soll ein entsprechendes Framework entwickelt werden, welches eben diesen Ansprüchen genügt. Dafür soll eine graphenbasierte Oberfläche generiert werden bei der Eingabe, Algorithmen und Ausgabe über Knotenpunkte verbunden und kombiniert werden können. Für die Knotenpunkte muss ein einheitliches Interface geschaffen werden, so dass sich diese beliebig kombinieren lassen. Über einen Plug-In Mechanismus soll dabei sichergestellt werden, dass neue Funktionalität auf möglichst einfache Art und Weise hinzugefügt werden kann.
November 11, 2011 11:11 Informatikzentrum, Seminarraum G30	Probevortrag CVMP Christian Lipski Probevortrag von Christian Lipski "Who Carez - Making Of"
October 14, 2011 13:00 Informatikzentrum, Seminarraum G30	BA-Vortrag Christian Brümmer Christian Brümmer Title "Avatar: Depth-based Multi-Camera Motion Capturing"
October 12, 2011 13:00 Informatikzentrum, Seminarraum G30	Optimization in Function Spaces Benjamin Hell (Universität Bayreuth) This talk shall give a brief overview of some aspects concerning the wide ﬁeld of optimization in function spaces, i.e. the optimization variables are functions. Although most research work done by me is of a rather theoretical nature with connections to applications this talk shall focus on techniques for obtaining solutions. Therefore the main emphasis will lie on numerical methods and programming aspects, while some more complicated analytical mathematics will only be presented when necessary or when they serve as interesting side notes. In general this talk shall just serve as a brief overview rather than a lecture on mathematics in the ﬁeld of optimization.
October 11, 2011 13:00 Informatikzentrum, Seminarraum G30	Optimal control based image sequence interpolation Kanglin Chen (Universität Bremen) The introduced interpolation methods are mainly based on finding an appropriate optical flow field, with which the objects in an initial image can be ``transported'' and ``warped'' to a certain time. To identify the optical flow field the interpolation problem is considered in the framework of optimal control governed by the transport equation. To improve the interpolation quality, the models are introduced so that the edges of the optical flow are preserved, the forward and backward interpolation are locally selected. Basically the smooth version of total variation and the active contours for segmentation are used.
September 26, 2011 14:00 Informatikzentrum, Seminarraum G30	The Portable Light Field Camera: Extended Depth of Field, Aliasing and Superresolution Paolo Favaro (Heriot-Watt University, Edinburgh) Portable light field cameras have demonstrated capabilities beyond conventional cameras. In a single snapshot, they enable digital image refocusing, i.e., the ability to change the camera focus after taking the snapshot, and 3D reconstruction. We show that they also achieve a larger depth of field while maintaining the ability to reconstruct detail at high resolution. More interestingly, we show that their depth of field is essentially inverted compared to regular cameras. Crucial to the success of the light field camera is the way it samples the light field, trading off spatial vs. angular resolution, and how aliasing affects the light field. We present a novel algorithm that estimates a full resolution sharp image and a full resolution depth map from a single input light field image. The algorithm is formulated in a variational framework and it is based on novel image priors designed for light field images. We demonstrate the algorithm on synthetic and real images captured with our own light field camera, and show that it can outperform other computational camera systems.
August 24, 2011 14:00 Informatikzentrum, Seminarraum G30	Perception in Real-Time Rendering Michael Guthe (Universität Marburg) Current graphics hardware is able to render scenes of striking realism in real-time: the ever growing processing power, memory size and bandwidth allows for the rendering of global illumination, realistic materials and smooth animations reserved to offline-rendering a few years ago. Nevertheless, the consumers expectations are almost increasing at the same rate. While traditional approaches become more efficient due to increasing processing power, the ultimate goal of realistically looking renderings is not a purely mathematical one. Due to the limitations of the human visual system, images that are far from realistic in a physical sense still look real. On the other hand seemingly minor inaccuracies can cause highly visible differences. Therefore it is necessary to consider human vision when generating images for both offline- and real-time rendering. Unfortunately estimating the visual difference itself can often be more time consuming than image generation. Therefore special visual models and pre-computed visual difference need to be used for interactive real-time rendering. The talk introduces two such models that were successfully applied in this context. The first one is tailored to perception of complex materials where especially compression to a manageable size is especially important. The second one proposes an efficient pre-computed difference measure for the reduction of complex polygon models. Based on the material with which the model is rendered a visually optimized reduction is performed. Finally an outlook to other fields that benefit from perception models is given.
August 17, 2011 13:00 Informatikzentrum, Seminarraum G30	Wim Sweldens' Building your own wavelets at home [pdf] Stefan Guthe Wavelets have been making appearance in many pure and applied areas of science and engineering. Computer Graphics with its many and varied computational problems has been no exception to this rule. In these notes we will attempt to motivate and explain the basic ideas behind wavelets and what makes them so successful in application areas.
July 15, 2011 13:00 Informatikzentrum, Seminarraum G30	How to get a Verdière-Matrix from a Permutahedron? Kai Lawonn In 1990 Colin de Verdière introduced a new graph parameter. This parameter is based on spectral properties of matrices associated with the graph. He showed that his number is invariant under taking minors. Additionally one can conclude topological properties to the graph with special values of the Verdière-Number. For example the graph is planar if and only if the parameter is less than 4. In general it is not well-known to get the Verdière-Matrix and the associated Verdière-Number of a given graph. In 2008 Ivan Izmestiev generalized the methods of Lovász to get a Verdière-Matrix from a polytope. This talk gives an introductive overview about the topic of the Verdière-Number and shows how to get a Verdière-Matrix from a special polytope the Permutahedron.
July 8, 2011 13:15 Informatikzentrum, IZ 161	Temporal Coherence and Adapted Computations for High-quality Real-Time Rendering Elmar Eisemann (Telecom ParisTech, Paris) Nowadays, there is a strong trend towards rendering to higher-resolution displays and at high frame rates. This development aims at delivering more detail and better accuracy, but it also comes at a significant cost. Although graphics cards continue to evolve with an ever-increasing amount of computational power, the processing gain is counteracted to a high degree by increasingly complex and sophisticated pixel computations. For real-time applications, the direct consequence is that image resolution and temporal resolution are often the first candidates to bow to the performance constraints (e.g., although full HD is possible, PS3 and XBox often render at lower resolutions). In order to achieve high-quality rendering at a lower cost, one can exploit temporal coherence (TC). The underlying observation is that a higher resolution and frame rate do not necessarily imply a much higher workload, but a larger amount of redundancy and a higher potential for amortizing rendering over several frames. In this session, we will investigate methods that make use of this principle and provide practical and theoretical advice on how to exploit temporal coherence for performance optimization. These methods not only allow us to incorporate more computationally intensive shading effects into many existing applications, but also offer exciting opportunities for extending high-end graphics applications to lower-spec consumer-level hardware.
June 17, 2011 13:00 Informatikzentrum, Seminarraum G30	Abschlussvortag zur Bachelorarbeit Paul Wiemann tbd
June 9, 2011 14:00 Informatikzentrum, Seminarraum G30	From video to models of natural phenomena for graphics applications Peter Hall (University of Bath, UK) Natural phenomena such as fire, smoke, trees, and water are ubiquitous; it is important for computer graphics to model them. Unfortunately modelling such phenomena is notoriously difficult computationally, so that a wide variety of techniques have been developed based on particles, textures, L-systems and plenty of user interaction. We will consider two case studies that show video is a potential source for acquiring models of natural phenomena, and the models produced can be easily controlled. Specifically, we will show how three-dimensional models of moving trees can be obtained from video with very little user interaction, how these models can serve as exemplars for automatic production of similar trees, and how the trees can be rendered and controlled in a wide variety of ways. We we also show how bodies of open water, from quiescent pools to breaking waves and waterfalls, can modelled through a single video camera.
May 27, 2011 13:00 Informatikzentrum, Seminarraum G30	Subdivision Surface Reduction Matthias Richter Diplomarbeit Matthias Richter
April 20, 2011 14:00 Informatikzentrum, Seminarraum G30	Reference Data Generation and Performance Analysis for Image Processing Daniel Kondermann (Heidelberg Collaboratory for Image Processing, Heidelberg) A commonly accepted hypothesis of the image processing community is that synthetic (rendered) reference data for image processing algorithms such as optical flow and stereo disparity estimation does not help in finding out whether they work in real-world environments. On the other hand, the creation of ground truth for real scenes is a difficult task, because no other measurement technique directly yields reference data of sufficiently high accuracy. In this talk I will discuss various ideas for ground truth generation. It turns out that this problem is closely linked to camera tracking, 3D scene reconstruction, material property estimation and related tasks. I will show our current approaches in this field and first results we obtained with respect to the comparison of real and synthetic image data.
February 18, 2011 13:00 Informatikzentrum, Seminarraum G30	Raising user experience by real-time physics simulation Michael Stengel User experience describes the impression of a user concerning a product or software. In the area of interactive software the application of physics simulation can improve usability and raise the joy of use. In this presentation two different examples in the areas of desktop applications and virtual reality are mentioned. Both have a benefit from using physics. It will be discussed in which way the simulation is integrated.
February 15, 2011 14:00 Informatikzentrum, Seminarraum G30	XFlow - Declarative Data Processing in XML3D Stefan John Our digital environment has become increasingly three-dimensional, but still the Web continues to remain comprised of two-dimensional elements. Several approaches exist to add 3D content to the Web, but none of them has found a widespread acceptance among web developers. XML3D is a new declarative approach that directly extends HTML5 to add interactive 3D graphics to the Web. The concept of XML3D follows a lightweight design and fully leverages existing web technologies, such as JavaScript, DOM, or CSS. As a joint research project of the Intel Visual Computing Institute (IVCI), the German Research Center for Artificial Intelligence (DFKI) and the Computer Graphics Lab of Saarland University, XML3D has recently spawned a W3C Incubator Group targeting the future of the 3D Web. With XFlow, a new dataflow-driven data processing mechanism was added to the XML3D specification. It further extends the scope of graphical effects achievable with XML3D. Simulating natural effects such as water surfaces, human skin, or vegetation requires mesh and image processing capabilities. In XML3D, meshes and shaders act as sinks for dataflow processes, allowing mesh and texture data to be the result of one or more data-processing scripts. XFlow introduces an implicit encoding of such processing graphs inside of HTML, considering various usability aspects. Due to the declarative approach, a transparent acceleration of the processing scripts can be achieved by offloading the actual calculations from the CPU onto available computing resources. As one of many applications, virtual avatars with realistic, animated faces embedded inside of a webpage have become possible.
February 2, 2011 11:00 Informatikzentrum, Seminarraum G30	Air-Liquid Interaction with SPH Julian Bader (Universität Freiburg) Air bubbles are a natural phenomenon which appears in everyday life. Thus, modeling air-liquid interaction can significantly improve the realism of fluid simulations such as Smoothed Particle Hydrodynamics (SPH). However, handling the large density ratio of water and air with SPH is problematic. This is due to high pressure forces which result in numerical instabilities. In order to circumvent these instabilities, the proposed air-liquid approach computes the two phases separately. The interaction is modeled by employing a two-way drag force. The method is capable of simulating typical air bubble phenomena, such as merging, deformation and volume-dependent buoyancy. To not explicitly represent the air surrounding the water, air particles are generated on-the-fly during simulation. Here, a heuristic is used that creates air bubbles only where they are likely to appear.
January 25, 2011 14:00 Informatikzentrum, Seminarraum G30	Very Low Power Graphics (or How to design a Mobile Graphics Chip) Stefan Guthe A variety of embedded systems require at least some kind of 3D graphics processing power. However, in a mobile setting power is the main constraint rather than features or performance alone. In this talk, we explore a very simple approach to design 3D graphics hardware tailored to the two mainstream 3D graphics APIs in the mobile market, OpenGL ES and DirectX. Besides achieving a functional low power 3D graphics implementation, we also need to take both hardware and software development requirements into account.
January 24, 2011 13:00 Informatikzentrum, Seminarraum G30	CUDA Expression Templates Paul Wiemann Many algorithms require vector algebra operations such as the dot product, vector norms or component-wise manipulations. Especially for large-scale vectors, the efficiency of algorithms depends on an efficient implementation of those calculations. The calculation of vector operations benefits from the continually increasing chip level parallelism on graphics hardware. Very efficient basic linear algebra libraries like CUBLAS make use of the parallelism provided by CUDA-enabled GPUs. However, existing libraries are often not intuitively to use and programmers may shy away from working with cumbersome and errorprone interfaces. In this paper we introduce an approach to simplify the usage of parallel graphics hardware for vector calculus. Our approach is based on expression templates that make it possible to obtain the performance of a hand-coded implementation while providing an intuitive and math-like syntax. We use this technique to automatically generate CUDA kernels for various vector calculations. In several performance tests our implementation shows a superior performance compared to CPU-based libraries and comparable results to a GPU-based library.
January 10, 2011 14:00 Informatikzentrum, Seminarraum G30	Multi-aperture imaging systems inspired by insect compound eyes Alexander Oberdörster (Fraunhofer-Institut für Angewandte Optik und Feinmechanik, Jena) Miniaturization of camera modules and reduction of their manufacturing cost is an important goal in many markets such as mobile phone cameras and automotive applications. Multi-aperture imaging systems inspired by insect compound eyes promise advances in both regards. A traditional optical system is a stack of lenses that images a certain field of view onto the image sensor. A multi-aperture-system consists of an array of microlenses (channels), each imaging a fraction of the total field of view onto its own small area on the image sensor, forming an array of microimages. With careful adjustment of the viewing directions of the channels, the focal lengths of the microlenses can be reduced to a fraction of the focal length of a single-aperture system. This decreases track length and increases depth of field. As each microimage spans only a small field of view, the optical systems can be simple. Because the microlenses are small -- they have a diameter of hundreds of microns and a sag of tens of microns -- they can be manufactured on wafer scale with microfabrication techniques. This makes production cost-effective and precise. To obtain a complete image from the partial images, they are combined electronically. For an accurate aligment of all pixels, the distortion of each microimage is derived from the optical design. Each pixel is treated as a measurement of radiance and placed on the image plane according to the viewing direction of the microlens, pixel position under the microlens, distortion at that position and parallax due to object distance. The final image is generated by interpolating between the known measurements.
November 29, 2010 13:00 Informatikzentrum, Seminarraum G30	Stereo Video Perception (Topics from ICIP 2010, Hong Kong ) Anita Sellent Scanning the contribution to the ICIP 2010 in Hong Kong, it becomes obvious that stereo video is a topic in which many researchers currently are interested. This talk will focus on stereo perception. First issue is the observation that watching a stereo video can cause headache. What causes this headache and what points have to be considered for recording and projection setup to avoid it? Next issue is the perception of compression artifacts in stereo-video, an important point, as the amount of raw-data for a stereoscopic film is twice as high as for a monoscopic film, but the content is highly redundant. The final issue of the talk is an evaluation of viewing setups to measure the quality of the images, that finally reach our eyes. After the talk we will discuss the experiences with stereo video we made in our research group.
November 1, 2010 13:00 Informatikzentrum, Seminarraum G30	Vorträge über das Dissertationsthema Martin Eisemann, Christian Linz, and Anita Sellent In den Vorträgen, die jeweils 45 Minuten dauern, stellen die Promotionskandidaten ihr Dissertationsthema vor und präsentieren ihre Forschungsergebnisse. Martin Eisemann, Titel: Error-Concealed Rendering Fotorealismus ist seit jeher eines der großen Ziele in der Computergrafik. Anstatt die Komplexität der Natur mit Standardmodellierungstools nachzubauen, gehen bildbasierte Ansätze den umgekehrten Weg und verwenden reale Aufnahmen zur Modellierung, da diese bereits per Definition fotorealistisch sind. Ein Nachteil dieser Variante ist jedoch, dass die Komposition oder Kombination mehrerer Quellbilder eine nichttriviale Aufgabe darstellt und häufig störende, sichtbare Artefakte im erzeugten Bild nach sich zieht. In dieser Dissertation verfolgen wir verschiedene Ansätze um Artefakte, welche durch die Komposition/ Kombination mehrerer Bilder in einer gemeinsamen Bilddomäne entstehen, zu verhindern oder zumindest abzuschwächen. Im Ergebnis liefern die vorgestellten Verfahren neue Bilder oder neue Ansichten einer Bildsammlung oder Videosequenz, je nachdem ob die Aufgabe dabei die Komposition mehrerer Bilder oder die Kombination mehrerer Videos verschiedener Kameras darstellt. Christian Linz, Titel: Beiträge zur Virtuellen Videokamera: von symmetrischen, dichten Korrespondenzkarten zu qualitativ hochwertigen bildbasierten Spezialeffekten 3D-Video mit Blickpunktnavigation ist eine neues digitales Medium welchem die Forschung in den letzten 10 Jahren viel Aufmerksamkeit gewidmet hat. Die meisten Verfahren rekonstruieren dabei die Szenengeometrie und schränken sich somit auf Lambertsche Szenen und synchron aufgenommene Eingabedaten ein. In diesem Vortrag beschreiben wir Beiträge zur "Virtuellen Videokamera", einem rein bildbasierten System zur Blickpunktnavigation, welches auf unsynchronisierten Eingabevideos arbeitet. Der Fokus liegt dabei auf der Schätzung dichter Korrespondenzkarten und auf der Synthese von Zwischenbildern. Das resultierende System eignet sich sowohl zur Produktion von räumlich-zeitlichen Spezialeffekten als auch zur Erzeugung stereoskopischer Sequenzen. Anita Sellent, Titel: Akkurate Bewegungsfeldbestimmung anhand von alternativen Bildgegebenheiten Projektionen der Szenenbewegung auf die Bildebene einer Kamera werden traditionell durch Betrachten von zwei aufeinanderfolgenden möglichst kurzen und scharfen Standbildern bestimmt. Die Modellierung von Bewegung durch die zeitliche Differenz zweier Bilder trifft allerdings einige Annahmen, die in realen Szenen nicht gegeben sind: so werden Szenenpunkte durch die unterschiedliche Bewegung von Objekten verdeckt oder aufgedeckt, Farbwerte verändern sich durch den Einfluß von Beleuchtung in der 3D Szene oder Bewegungen zwischen zwei Bildern umfassen mehrere Pixel. In dem Vortrag sollen die klassische Bewegungsformulierung, die Ursache des zeitlichen Aliasing und Ansätze zu dessen Vermeidung dargestellt werden.
October 26, 2010 15:30 Informatikzentrum, Seminarraum G30	Python für Computergraphiker Thomas Neumann and Stephan Wenger Der Vortrag bietet eine Einführung in Python und SciPy sowie einige Live-Demos.
October 22, 2010 13:00 Informatikzentrum, Seminarraum G30	Multi-Video Foreground Segmentation Julia Wolf Im Forschungsfeld der Foto- und Videoverarbeitung wird unter anderem an der automatischen Segmentierung eines Bildes in seine Vorder- und Hintergrundanteile gearbeitet. Die Verfahren sind für Einzelbilder bereits sehr stabil und benötigen nur wenige Benutzerinteraktionen. Es ist möglich, viele dieser Algorithmen auf die Verarbeitung von Videos zu erweitern. Dort wird versucht, möglichst viele Bilder hintereinander automatisch zu segmentieren. Bei anspruchsvollen Szenen mit groÃŸen Bewegungen oder komplexem Hintergrund bleibt die automatische Segmentierung über mehrere Bilder jedoch unzuverlässig, so dass der Anwender oft manuelle Nachbesserungen vornehmen muss. Bei der Verwendung von mehreren Kameras in einer Szene, mit denen das Vordergrundobjekt aus verschiedenen Blickwinkeln aufgenommen werden kann, muss jedoch ein Vielfaches an Material ausgewertet und manuell angepasst werden. Entgegen des allgemeinen Ansatzes, jeden Videostrom getrennt voneinander zu bearbeiten, wird in dieser Arbeit ein Verfahren entwickelt, dass die Ergebnisse der einzelnen Bilder unterschiedlicher Videoströme miteinander kombiniert. Es soll durch den Informationsgewinn eine Verbesserung der Einzelbildergebnisse, der Gesamtbearbeitungszeit und folglich eine Verringerung der manuellen Korrekturen erreicht werden. Zusätzlich dazu wird ein Algorithmus entwickelt, der automatisch schlechte Segmentierungen detektiert und dem Benutzer zur manuellen Nachbesserung anbietet. Als Ergebnis dieser Arbeit ist ein Verfahren entstanden, das einen Algorithmus zur Trennung von Vorder- und Hintergrundinformationen für einen einzelnen Videostrom auf die Verwendung von mehreren Kameras adaptiert und in Verknüpfung mit der Detektion und Anpassung von schlechten Segmentierungen funktioniert. Der Algorithmus zur kameraübergreifenden Verwendung der Ergebnisse aus unterschiedlichen Videoströmen bringt einen deutlichen Vorteil gegenüber anderen Verfahren.
September 23, 2010 14:00 Informatikzentrum, Seminarraum G30	Adapted Computations and Representations for Real-time Graphics Elmar Eisemann (Telecom ParisTech, Paris) Recent advances in computer graphics have contributed to a surprising increase in complexity with respect to geometry as well as the simulation of physical phenomena (such as shadows, refraction, or depth of field). Approximating and visualizing geometry consisting of tens of millions of polygons simultaneously tested for collision or visibility is becoming increasingly common. Involving the complete virtual environment poses a significant computational challenge. We will show how simplified representations, suitable approximations of physical effects, and perceptual findings can be exploited to push the boundaries of image synthesis and enable detailed, yet efficient rendering solutions.
September 13, 2010 13:00 Informatikzentrum, Seminarraum G30	Enhanced Poisson Image Editing Daniel Gohlke Mit Hilfe der Poisson-Gleichung, die vor allem in der Bildbearbeitung große Bedeutung erlangt hat, lassen sich Objekte nahtlos in andere Bilder einfügen. Für die erfolgreiche Anwendung der Gleichung sind jedoch bestimmte Vorbedingungen zu erfüllen. Das nahtlose Einfügen funktioniert am Besten, wenn die Farbdifferenz in den Randgebieten sehr ähnlich ist und die Objektkanten im Quell- und Zielbild sich möglichst gut überlagern. Im Zuge dieser Arbeit ist ein Verfahren entwickelt worden, das bestehende Konzepte für das nahtlose Einfügen umsetzt und erweitert. Dabei ist das "Poisson Image Editing" umgesetzt und um die Suche der optimalen Kontur mit Hilfe des "Drag-and-Drop Pasting" Verfahrens erweitert worden. Das Hauptaugenmerk dieser Arbeit liegt jedoch auf der überlagerung von starken Objektkanten. Es wird ein Verfahren vorgestellt, dass zum Finden und Zuordnen von Objektkanten im Quell- und Zielbild verwendet werden kann. Nach der erfolgreichen Zuordnung der Objektkanten wird die Verschiebung zwischen den Objektkanten ermittelt. Anschließend wird das Quellbild so verzerrt, dass die passenden Objektkanten sich überdecken. Da dies zu starken Verzerrungen am Rand führen kann, ist es außerdem möglich die Kanten in das Bild hinein zu verfolgen und die Verschiebungen entlang wichtiger Kanten festzulegen. Dies führt zur Erhaltung der Kantenform im Zielbild und zur Verbesserung des optischen Eindrucks in der Randregion. Zusätzlich wird das Verfahren für das nahtlose Einfügen von Objekten in andere Bilder in einen pyramidenbasierten Ansatz eingebettet. Dadurch können auch Bilder mit unterschiedlichen Schärfegraden ineinander eingef ügt werden. Die Korrespondenzfindung zwischen den Bildern wird durch die Verwendung von SIFT-Features automatisiert. Neben der Ermittlung von einer Korrespondenz zwischen den Bildern ist es möglich, für bestimmte Bildbereiche mehrere Korrespondenzen zu finden und somit ein Objekt an mehreren Stellen im Zielbild zu platzieren. Nach der Korrespondenzfindung erfolgt die Berechnung der optimalen Bilddimensionen für das Einfügen, so dass die Bilder möglichst gut für die Anwendung des Verfahrens geeignet sind. Das Einfügen erfolgt dann mit Hilfe des des oben genannten Verfahrens. Mit dem in dieser Arbeit entwickelten Programm ist es möglich, einige Probleme die bei der Verwendung des "Poisson Image Editing" Verfahrens auftreten zu beseitigen und optisch ansprechende Ergebnisse zu erzielen. Vor allem die Erhaltung von Bildkanten innerhalb des eingefügten Bereichs trägt deutlich zur Verbesserung des optischen Eindrucks des zusammengesetzten Bildes bei.
August 23, 2010 14:00 Informatikzentrum, Seminarraum G30	Projektarbeit: Erstellung eines BRDF-Editors für das Reflektanzverhalten von Oberflächen in refrakti Alexander Schäfer Um eine künstliche 3D-Szene realistisch wirken zu lassen, bedarf es authentischen Oberflächen-Materialien bzw. einem glaubwürdigen Reflektanzverhalten der Szenenobjekte. Ein gängiges und schnelles Verfahren ist die Auswertung einer Bidirektionalen-Reflektanz-Verteilungs-Funktion(BRDF), mit welcher man verschiedene Materialien mathematisch beschreiben kann. Bisher vernachlässigt dieses Modell die Tatsache, dass sich das Reflektanzverhalten vieler Materialien, je nach dem welches Medium das Objekt umgibt, verändert. So sieht ein Kleidungsstück unter Wasser anders aus als an der Luft. Im Rahmen der Forschungsarbeiten des Instituts für Computergrafik, TU Braunschweig, und des MPI für Informatik, Saarbrücken, soll deshalb das BRDF-Modell zur Ermittlung des Reflektanzverhaltens von Oberflächen in Abhängigkeit zum umgebenden Medium entsprechend erweitert werden. Im Kontext dieses Forschungsvorhabens liefert diese Arbeit ein passendes Werkzeug zur Visualisierung und Auswertung der entstandenen Messdaten, und bietet dem Benutzer die Möglichkeit das Reflektanzverhalten der realen Bilddaten mit einem beliebigen, mathematischen Modell zu vergleichen.
August 17, 2010 14:00 Informatikzentrum, Seminarraum G30	Interactive Fur Shaping and Rendering Hanqlu Sun (VR, Visualization and Imaging Research Centre, The Chinese University of Hong Kong ) Furry surfaces are crucial in representing the realistic appearance of virtual creatures and cartoon-style objects/bodies. It is highly demanding to model and render the realistic furry effects in interactive gaming and virtual environments. Most of the hair/fur modeling systems proposed geometry-based representations so the systems do not directly support interactive modeling and rendering of virtual furry creatures. Our work is motivated for representing the realistic furry surfaces based on the non-uniform layered approach, and supporting users the interactive tools to intuitively shape dense, messy fur over the bodies with the realistic rendering effects. These include fur combing, wind blowing, pulling, interpolating, smoothing and disturbing, thus users can intuitively design and manipulate the furry surfaces over the bodies with simple user input. Further, we developed layered shadow maps for the realistic self-shadowing effects of fur, which can significantly enhance the realistic appearance of furry creatures. Using the interactive tools, users can intuitively create the furry shapes of virtual creatures, and visualize the realistic rendering of edited fur instantly. Our interactive fur system utilizes GPU-accelerated processing, and supports the intuitive user input for shaping the furry surfaces of virtual creatures. Also, other current research projects we have worked on will be briefly introduced at the end as well.
July 23, 2010 14:00 Informatikzentrum, Seminarraum G30	Strömungsvisualisierung Daniel Weißkopf (Universität Stuttgart)
June 24, 2010 14:00 Informatikzentrum, Seminarraum G30	Perceptual Research Methodology and its relevance for Computer Graphics Douglas Cunningham Perceptual psychology and computer graphics ask many questions that are formally similar. These questions relate to how one can -- with rather limited resources -- extract, represent, and manipulate targeted portions of the vast amount of information present in the physical world. Over the last 150 years, perceptual psychologists have developed and refined a wide variety of experimental methods, and have gathered a wealth of detailed information about the algorithms that underlie human perceptual processes. Since many of the tasks and challenges explored in computer graphics are similar to those faced in human perception, and since humans are often the end-user of computer generated imagery, computer scientists are increasingly adapting knowledge about human perception to develop perceptually-inspired computer graphics algorithms. Moreover, computer graphics researchers are increasingly being asked to prove that newly developed techniques meet specific claims, such as "Are the images generated by the new method really indistinguishable from a photograph?"; "If not, why not?"; "Do the new visualizations really improve the performance of experts on specific tasks?" A firm understanding of perceptual research methodology will now only make it easier to comprehend and utilize existing knowledge about human perceptual capabilities, but will also enable you to ask and answer similar questions for your algorithms. In this talk, I will provide a brief overview of perceptual methodology and some of the fundamental assumptions that lie behind it.
June 10, 2010 14:00 Haus der Wissenschaft	Visual Computing Workshop Ralph Bruder (TU Darmstadt), Peter Elsert (FhG-HHI & HU Berlin), Oliver Grau (BBC Research & Development, London), Andreas Kolb (Siegen University & speaker DFG-GK 1564), Bernd Schiele (TU Darmstadt & MPI Informatik), Hartmut Schirmacher (Visage Imaging GmbH), Hans-Peter Seidel, Philipp Slusallek (Intel Visual Computing Institute & DFKI Saarbrücken, [video_talk] [video_discussion] ), Aljoscha Smolic (Disney Research Zurich), and Timo Stich Webseite
April 26, 2010 14:00 Informatikzentrum, Seminarraum G30	An introduction to space weather, for computer scientists Kai Ruhl Space weather are solar and cosmic background effects on satellites and astronauts, the ionosphere, and ground systems. Our solar system is not quite as empty as the word "space" implies: Photons, electrons and protons as well as ions from the Sun fill most of the heliosphere, driving back the galactic cosmic rays that would otherwise dominate. This talk aims at providing an overview of the primary concepts used in space weather, suited to the understanding of computer scientists (who might not necessarily be versed in solar physics). A packet of photons and particles will be followed from the surface of the sun to the surface of the earth, describing basic interactions on its way. Advanced topics will not be covered.
April 12, 2010 17:00 Informatikzentrum, Hörsaal 160	Deklarative XML-Verarbeitung mit Anwendungen in der Linguistik und im Sport Dietmar Seipel Die komfortable und effiziente Verarbeitung von XML-Dokumenten und XML-basiertem Wissen spielt heute eine zunehmend wichtige Rolle, z.B. zur Verwaltung und zum Austausch komplexer Daten oder im Semantic Web. Zum Zugriff auf und zur Transformation von XML--Strukturen haben wir die deklarative Anfrage-, Transformations- und Updatesprache FnQuery entwickelt und in verschiedenen Anwendungen erprobt. In einem Projekt zur Analyse von Varianz in Sprache und Genomen werden schwach in XML strukturierte Wörterbücher aufbereitet und analysiert. Wir haben dazu ein deklaratives Toolkit zur Annotation von Wörterbüchern entwickelt, das auf XML- und Prolog-Technologie basiert. Eines der Hauptziele des Projektes ist die Erstellung einer Metalemmaliste als Grundlage für den Strukturvergleich mit bioinformatischen Daten. Metalemma ist dabei die als Wort in der Gegenwartssprache angesiedelte Referenzeinheit, auf die - soweit möglich - die sprachlichen Entsprechungen aus Dialekträumen (diatopische Varianz) und Sprachstufen (diachronische Varianz) abgebildet werden. Es zeigte sich, daß der deklarative Ansatz in Prolog viel lesbarer, flexibler, verläßlicher und sogar schneller ist als eine alternative Implementierung, die vorher in Java und XSLT für das TextGRID- CommunityProjekt gemacht worden war. In einem anderen Projekt werden räumlich/zeitliche Spielsequenzen im Sport (Basketball, Tennis) in XML gespeichert und mit Hilfe von deklarativen Anfragen bzw. temporalem Data Mining analysiert.
March 29, 2010 13:00 Informatikzentrum, Seminarraum G30	Rotationsinvariante Texturoptimierung für Super-Resolution und Detailhalluzination Lea Lindemann Beispielbasierte Textursynthese dient normalerweise dazu, aus einem kleinen Eingabepatch eine größre Textur mit höherer Auflösung zu erzeugen. Problematisch dabei ist, daß meist nur eine Textur erzeugt wird, welche zwar eine höhere Auflösung hat, die Details jedoch gleich bleiben und nicht mit skaliert werden. Die bisherige Forschung in diesem Gebiet unterliegt dabei noch vielen Einschränkungen, so müßen exakte Größnkorrespondenzen meist von Hand vorgegeben werden, und die Bilder müßen bereits paßend ausgerichtet sein. Es ist jedoch aus verschiedenen Gründen nicht immer einfach paßende Eingabebilder zu erzeugen. Ein Beispiel wäre ein Bild, welches man aus dem Internet geladen hat und welches man gerne in einer höheren Auflösung hätte, ohne daß es verschwommen erscheint. Im Grunde existiert in diesem Falle kein Eingabebild, welches man zum Hochskalieren verwenden könnte. Superresolution Ansätze können zwar niedrige und sehr hohe Frequenzen erhalten, haben aber das Problem, daß mittlere Frequenzen, meist verloren gehen, oder nicht synthetisiert werden. Aber vielleicht hat man ähnliche Bilder der vorkommenden Materialien gegeben. Diese könnte man eventuell verwenden. Leider ist die notwendige Voraußetzung der gleichen Perspektive dabei meist verletzt. In dieser Arbeit soll untersucht werden, inwieweit eine neuartige Textursynthese mit rotations- und beleuchtungsinvarianten Nachbarschaftsbeschreibungen, das Problem der Perspektive und der neu hinzuzufügenden Details lösen kann. Dazu benötigt man eine genaue Analyse der Stärken und Schwächen eines solchen Ansatzes. Ist es wirklich sinnvoll eine genaue übereinstimmung mit dem Originalbild zu erhalten, oder kann es nicht von Vorteil sein, dem Algorithmus leichte Freiheiten zu gewähren? Dafür wird ein Optimierungsalgorithmus vorgestellt, der sich genau mit diese Fragen beschäftigt.
February 25, 2010 14:00 Informatikzentrum, Hörsaal 160	Modeling the planetary nebula IC418: a combined approach using stellar and nebular model Christophe Morisset We present a coherent stellar and nebular model reproducing the observations of the Planetary Nebula IC418. We want to test whether a stellar model obtained by fitting the stellar observations is able to satisfactory ionize the nebula and reproduce the nebular observations, which is by no mean evident. This allows us to determine all the physical parameters of both the star and the nebula, including the abundances and the distance. We used all the observational material available (FUSE, IUE, STIS and optical spectra) to constrain the stellar atmosphere model performed using the CMFGEN code. The photoionization model is done with Cloudy_3D, and is based on CTIO, Lick, SPM, IUE and ISO spectra as well as HST images. More than 140 nebular emission lines are compared to the observed intensities. We reproduce all the observations for the star and the nebula. The 3D morphology of the gas distribution is determined. The effective temperature of the star is 36.7kK. Its luminosity is 7700 solar luminosity. We describe an original method to determine the distance of the nebula using evolutionary tracks. No clumping factor is need to reproduce the age-luminosity relation. The distance of 1.25 kpc is found in very good agreement with recent determination using parallax method. The chemical composition of both the star and the nebula are determined. Both are Carbon-rich. The nebula presents evidence of depletion of elements Mg, Si, S, Cl (0.5 dex lower than solar) and Fe (2.9 dex lower than solar). This is the first self-consistent stellar and nebular model for a Planetary Nebula that reproduces all the available observations ranging from IR to UV, showing that the combined approach for the modeling process leads to more restrictive constraints and, in principle, more trustworthy results.
February 25, 2010 14:00 Informatikzentrum, Hörsaal 160	Shape 2010: 3D Strahlungstransport für die Visualisierung astrophysikalischer Phänomene Wolfgang Steffen Das Programm Shape wurde ursprünglich zur 3D-Modellierung der Struktur und Kinematic astrophysikalischer Nebel geschrieben. Shape ist das erste astrophysikalische Simulationsprogramm ist, das interaktive 3D-Graphiktechniken zur Modelerzeugung verwendet. Jetzt wurde aber zusätzlich 3D-Strahlungstransport eingebaut, was realistischere Darstellungen erlaubt. Das neue Animationsmodul und "Texturing" und andere Neuheiten erweitern deutlich die Anwendungsmöglichkeiten in der Visualisierung und astrophysikalischen Forschung.
February 8, 2010 13:00 Informatikzentrum, Seminarraum G30	C for CUDA for and from Dummies Martin Eisemann C for CUDA is an extension to the C language to exploit the processing power of NVidia GPUs for general purpose computation. While for a long time now it seemed that Computer Graphics does not benefit all too much from this, due to GLSL, it turned out, that especially in Vision tasks or specialized applications C for CUDA can give your application a real boost in speed. Plus, it can be simple, if you know the right tools and have the right framework (which you will have after this talk! Hooray!). In this talk I will report on my first hand on experience with CUDA. I will give you an introduction into the basic memory management, kernel execution on the GPU and some other useful stuff. After this talk you will be able to directly write your own CUDA programms, right from the start. [pdf der Vortragsfolien]
January 11, 2010 13:00 Informatikzentrum, Seminarraum G30	Visualisierung von Multispektralbildern anhand spektraler Komponenten David Ben Yacov Spektraldaten, die mit ortsauflösenden Bildsensoren aufgenommen wurden, liegen zunächst in einer Form vor, bei der zwei Dimensionen eines Datensatzes den Bildkoordinaten einer Flächenkamera und die dritte dem Intensitätsverlauf über der Wellenlänge entsprechen. Auch nach geeigneter Aufbereitung der Spektren (Normierung und Differenzierung) sind ihre Komponenten, die z.B. den Anteil chemischer Substanzen in bestimmten Teilen einer Szene charakterisieren, nicht ohne weitere Auswertung am spektralen Verlauf erkennbar. In dieser Arbeit wurden die Pixel von Multispektralbildern durch geeignete Verfahren so klassifiziert, dass in den Bildern Regionen mit bestimmten spektralen Eigenschaften segmentiert und visualisiert werden können. Dadurch soll es möglich gemacht werden z.B. den Klebstoffanteil in Spänevliesen (mit Klebstoff vermischte Flachspäne für die Spanplattenproduktion) nachzuweisen. Das für diese Aufgabe entwickelte System wird in diesem Vortrag vorgestellt.
December 7, 2009 13:00 Informatikzentrum, Seminarraum G30	Data Clustering using Affinity Propagation Christian Lipski Clustering data is an everyday task in computer graphics with an already wide selection of available algorithms. We will take a look at affinity propagation, a new technique that is based on message passing among data points. The vital benefit is that the amount of clusters is not strictly predefined, but emerges from the data. In addition, the very generic approach lends itself to a wide variety of application. Together with speed-up strategies developed in the graphics community, it can be used for large data sets (i.e., images).
November 5, 2009 13:00 Informatikzentrum, Seminarraum G30	Local Model of Eye Adaption for High Dynamic Range Images Benjamin Meyer In the real world, the human eye is confronted with a wide range of luminances from bright sunshine to low night light. Our eyes cope with this vast range of intensities by adaptation; changing their sensitivity to be responsive at different illumination levels. This adaptation is highly localized, allowing us to see both dark and bright regions of a high dynamic range environment. In this paper we present a new model of eye adaptation based on physiological data. The model, which can be easily integrated into existing renderers, can function either as a static local tone mapping operator for single high dynamic range image, or as a temporal adaptation model taking into account time elapsed and intensity of preadaptation for a dynamic sequence. We finally validate our technique with a high dynamic range display and a psychophysical study. [pdf der Vortragsfolien]
October 26, 2009 13:00 Informatikzentrum, Seminarraum G30	Integrating NonPhotorealistic Visual Effects into the Virtual Video Camera System Alexander Schäfer Visuelle Effekte lassen einen Film zu einem Erlebnis werden. Aus diesem Grund wird für aktuelle Kinofilme ein gewaltiger Zeit- und Kostenaufwand in Kauf genommen. Im Rahmen dieser Bachelorarbeit werden solche Nicht-Photorealistischen Effekte deshalb besonders kostengünstig realisiert. Als Grundlage dient dazu das virtuelle Videokamera-System, welches bereits am Computergrafik-Institut der TU-Braunschweig entwickelt wurde. Die zentralen Probleme beim Erzeugen eines Videoeffektes sind die Maskierung des gewünschten Zielobjektes in der Szene und das zeitlich kohärente Zeichnen dieses Effekts im Verlauf der Videosequenz. Eine Besonderheit stellt dabei die Möglichkeit zur zeitlichen Manipulation des Videos durch das virtuelle Videokamera-System dar. Vor diesem Hintergrund wurden die vier Bewegungseffekte "Time Lapse", "Temporal-Flare", "Particle-Effect" und "Speedlines" umgesetzt.
October 13, 2009 13:00 Informatikzentrum, Seminarraum G30	Making Shape from Shading Work for Real-World Images Anita Sellent Although shape from shading has been studied for almost four decades, the performance of most methods applied to real-world images is still unsatisfactory: This is often caused by oversimplified reflectance and projection models as well as by ignoring light attenuation and nonconstant albedo behavior. Vogel et al. address this problem by poposing a novel approach that combines three powerful concepts.
September 28, 2009 13:00 Informatikzentrum, Seminarraum G30	Combining automated analysis and visualization techniques for effective exploration of high-dimensio Georgia Albuquerque Visual exploration of multivariate data typically requires projection onto lower-dimensional representations. The number of possible representations grows rapidly with the number of dimensions, and manual exploration quickly becomes ineffective or even unfeasible. This paper proposes automatic analysis methods to extract potentially relevant visual structures from a set of candidate visualizations. Based on features, the visualizations are ranked in accordance with a specified user task. The user is provided with a manageable number of potentially useful candidate visualizations, which can be used as a starting point for interactive data analysis. This can effectively ease the task of finding truly useful visualizations and potentially speed up the data exploration task. In this paper, we present ranking measures for class-based as well as non class-based Scatterplots and Parallel Coordinates visualizations. The proposed analysis methods are evaluated on different datasets.
September 21, 2009 13:00 Informatikzentrum, Seminarraum G30	Finding the fraud: Matching and comparing photographies of art Dirk Fortmeier Seitdem Menschen für Kunst Geld bezahlen gibt es Fälschungen und somit das Bedürfnis den Fälschern auf die Schliche zu kommen. Einige Fälschungen sind leicht zu erkennen, andere nur durch sehr genaues hinschauen. Im Rahmen dieses Projekts wurden Methoden erdacht und evaluiert um Photographien von Gemälden und Kunstwerken mit Photographien ihrer Originale zu vergleichen. Die zentralen Probleme die dabei auftraten sind einerseits das Matching (Eliminierung der Unterschiedlichen Blickwinkel und Aufnahmebedingungen) sowie anderseits der anschließnde Vergleich. [pdf der Vortragsfolien]
September 7, 2009 13:00 Informatikzentrum, Seminarraum G30	The future of driver assistance Tobi Vaudrey Imagine a futuristic world where cars drive themselves. In New Zealand alone, there have been about driving 5000 fatalities over the past 10 years. Think of the reduction in accidents as cars are always looking at the road and making decisions based on its perception of the environment. The car will never get drunk, never fall asleep at the wheel, be always attentive and never suffer from road rage! This seems like a far-distant possibility that is only in the minds of science fi ction writers, such as those of Star Trek. But this reality is perhaps not so far away. We are still a while of the future depicted above, but there are smart cars that do take control of vehicles already, even if the driver is not aware. My research is on vision based driver assistance systems, in other words, I try and create eyes for cars. In this talk I will cover the basics of vision based environment perception: removing harmful illumination effects, stereo disparity estimation (distance), optical flow (2D motion), and scene flow (3D motion). Hopefully this brief introduction will spark some passion in driver assistance, and help save lives in the future. [pdf der Vortragsfolien]
August 31, 2009 13:00 Informatikzentrum, Seminarraum G30	MultiView Camera Calibration Denis Bose Die Kamerakalibrierung ist ein bedeutender Schwerpunkt in der Computer Vision und auch Computergraphik, bspw. im Bereich Image- und Video-based Rendering. Obwohl es verschiedenste Ansätze gibt, die gute Ergebnisse liefern können, sind diese in ihrer Bedienbarkeit und damit benötigtem Zeitaufwand sehr unterschiedlich. Der Traum bleibt weiterhin ein vollautomatisches System, welches einem erlaubt einfach eine Videokamera auf Aufnahme zu stellen und direkt die entsprechenden Kalibrierungsdaten liefert. Ein paar solcher Ansätze existieren bereits, insbesondere die Forschungsgruppe um Marc Pollefeys oder die Arbeit von Noah Snavely haben sich hier hervorgetan. Nachteil dieser Verfahren ist, dass der der zeitlich benötigte Aufwand meist sehr hoch und vor allem entweder quadratisch in der Anzahl zu untersuchender Bilder ist oder mit Drifts zu kämpfen hat. Insbesondere bei Multi-Kamera Systemen ist der Aufwand schnell sehr hoch und tausende von Bildern müssen verarbeitet werden. Ziel dieser Arbeit ist es ein möglichst leicht zu bedienendes System zu entwerfen, welches einem die internen und externen oder nur externen Kameraparameter für ein aus mehreren Kameras bestehendes Video-based Rendering System liefert. Dabei soll auf dem Sparse Bundle Adjustment Package â€žBundlerâ€œ von Noah Snavely aufgesetzt werden und dieses in das am ICG entwickelte System zum Bestimmen des zeitlichen Versatzes von Videos integriert werden, damit man letztendlich aus unsynchronisierten Videos, synchronisierte Videos mit den entsprechenden Kameraparametern erhält. In einem nächsten Schritt werden dann verschiedene Ansätze ausgetestet, welche die Berechnungszeit optimieren sollen. Bspw. zur Berechnung des i-ten Bildes nur jedes n-te Bild heranziehen; nur Bilder in einem bestimmten Zeitfenster verwenden; oder Auswahl geeigneter Repräsentanten aus der kompletten Sammlung an Bildern. Diese Ansätze werden einer Qualitätsanalyse unterzogen in Hinsicht auf die Ergebnisse des Originalalgorithmus. [pdf der Vortragsfolien] [Weiterführende Informationen]
August 24, 2009 13:00 Informatikzentrum, Seminarraum G30	Genetic Morphs Daniel Gohlke Optical Flow is widely used in the graphics and vision community for estimating the flow or warp field that matches one image with another, but optical flow is a highly ill-posed problem. Evolutionary or genetic algorithms are often used in computer science to solve such ill-posed problems. These are based on the principles of selection, mutation and recombination. This talk will present a framework based on genetic algorithms to estimate flow fields and tries to improve on existing optical flow algorithms by adding their results to the initial population. [ppt der Vortragsfolien]
August 24, 2009 13:00 Informatikzentrum, Seminarraum G30	Video Matting Julia Wolf Matting is the process of estimating a foreground object in an image and placing this object into another surrounding, i.e. image or video. For complex objects like hair or transparent objects a simple binary map is insufficient for describing the object and a more complex alpha matte with continuous values is needed. While many robust methods exist for still images, matting of complete videos is still a difficult and labour-intensive work. In this talk an extension of the Spectral Matting method by Levin et al. towards video matting is presented. Given certain assumptions on the scene, the presented method is robust and very easy to use. [ppt der Vortragsfolien]
August 3, 2009 13:00 Informatikzentrum, Seminarraum G30	Texture Synthesis with Transformed Neighborhoods with Application to SuperResolution Lea Lindemann Texture synthesis is usually used to create a larger texture image out of a small texture patch, so that the output image looks similar to the small patch when looking only at a small part of the output texture image. But texture synthesis can also be used for other task, such as image completion, super-resolution and more. In this talk an adaptation of the texture synthesis algorithm of Kwatra et al.'s "Texture Optimization for Example-based Synthesis" is presented, which allows for perspectively transformed synthesis and is applicable for super-resolution. [pdf der Vortragsfolien]
July 27, 2009 13:00 Informatikzentrum, Seminarraum G30	Infrared Tracking: Getting Started Andrea Keil Human Computer Interaction regarding Gaze Tracking has been an interesting research topic in the last years, but most of the systems use head-mounted special gear that limit the subjects significantly, are complicated to use and may be quite expensive. In my diploma thesis, I aim to develop infrared tracking applications -such as eye tracking- with an easy interface, meaning no headgear, no high definition camera and an easy setup, working in real time. Using the specific characteristics of infrared light towards the human eye, one can estimate not only the eye position in the image but the gaze, meaning the viewing direction, as well. Additionally, Infrared Tracking can be applied to the human body, using a special invisible infrared pen to mark the body for motion capturing or hands for gesture recognition; or to mark paper, letters, etc. for safety and encoding. Next Monday will be about our starting point: "Gaze Tracking and the related work." [pdf der Vortragsfolien]
July 20, 2009 13:00 Informatikzentrum, Seminarraum G30	Modeling Human Color Perception under Extended Luninance Levels Benjamin Meyer Display technology is advancing quickly with peak luminance increasing significantly, enabling high-dynamic-range displays. However, perceptual color appearance under extended luminance levels has not been studied, mainly due to the unavailability of psychophysical data. Therefore, we conduct a psychophysical study in order to acquire appearance data for many different luminance levels covering most of the dynamic range of the human visual system. These experimental data allow us to quantify human color perception under extended luminance levels, yielding a generalized color appearance model. Our proposed appearance model is efficient, accurate and invertible. It can be used to adapt the tone and color of images to different dynamic ranges for crossmedia reproduction while maintaining appearance that is close to human perception. [pdf der Vortragsfolien]
July 13, 2009 13:00 Informatikzentrum, Seminarraum G30	SEP 2009 Georgia Albuquerque In this colloquium we revise on the SEP projects of this semester. The two student groups who participated in the SEP will present their achieved results.
July 10, 2009 14:00 Informatikzentrum, Seminarraum G30	A Superresolution Framework for High-Accuracy Multiview Reconstruction Bastian Goldlücke Focus of this talk are the current state-of-the-art methods for 3D reconstruction from multiple calibrated views which were developed in our group. Based on a convex formulation for the 3D reconstruction problem, an initial 3D model is obtained. The geometry is further refined in a combined variational approach to jointly estimate a displacement map and a super-resolved texture for the model. The super-resolution approach to texture reconstruction allows to obtain fine details in the texture map which surpass individual input image resolution. Some of the interesting mathematical background can be applied quite generally and is briefly discussed. This includes convex relaxation techniques for global optimization of certain total variation based energy functionals, as well as an algorithm for solving partial differential equations on surfaces.
July 6, 2009 13:00 Informatikzentrum, Seminarraum G30	Recent Trends in Interactive Multi-Image Segmentation Christian Lipski Extraction of meaningful regions in images has been an active research topic for decades. Recently, coherent detection of such regions across image sequences received special attention. Especially when high-quality output is demanded by the application, e.g., in video matting, such systems are designed to incorporate user input that steers and improves the segmentation algorithm. The talk will cover a selection of recent work in this area. We will identify recent trends and see how we can relate them to other areas of research, such as interactive correspondence estimation. [pdf der Vortragsfolien]
June 29, 2009 13:00 Informatikzentrum, Seminarraum G30	EuroVis 2009 Georgia Albuquerque I will talk about two of the most interesting papers presented at the Eurographics/IEEE Symposium on Visualization June 10 - 12, 2009 in Berlin, Germany. In the first article: "Splatting the Lines in Parallel Coordinates", the authors presented two method to enhance the visibility of clusters using parallel coordinates. In the second one: "Selecting good views of high-dimensional data using class consistency", the authors present a measure to evaluate scatterplots of data sets considering class information. [pdf der Vortragsfolien] [MP3 des Vortrags]
June 26, 2009 14:00 Informatikzentrum, Seminarraum G30	Efficient and accurate visualization of complex light sources Stefan Kniep We present a new method for estimating the radiance function of complex area light sources. The method is based on Jensens photon mapping algorithm. In order to capture high angular frequencies in the radiance function, we incorporate the angular domain into the density estimation. However, density estimation in position-direction space makes it necessary to and a tradeoff between the spatial and angular accuracy of the estimation. We identify the parameters which are important for this tradeoff and investigate the typical estimation errors. We show how the large data size, which is inherent to the underlying problem, can be handled. The method is applied to different automotive tail lights. It can be applied to a wide range of other real-world light sources.
June 15, 2009 14:00 Informatikzentrum, Seminarraum G30	Compressed Sensing Stephan Wenger The dogma of signal processing maintains that a signal must be sampled at a rate at least twice its highest frequency in order to be represented without error. However, in practice, we often compress the data soon after sensing, trading off signal representation complexity (bits) for some error (consider JPEG image compression in digital cameras, for example). Clearly, this is wasteful of valuable sensing resources. Over the past few years, a new theory of "compressive sensing" has begun to emerge, in which the signal is sampled (and simultaneously compressed) at a greatly reduced rate. Compressive sensing is also referred to in the literature by the terms: compressed sensing, compressive sampling, and sketching/heavy-hitters. [pdf der Vortragsfolien]
June 8, 2009 14:00 Informatikzentrum, Seminarraum G30	Fast Reconstruction of the World from Photos and Videos Jan-Michael Frahm (University of North Carolina at Chapel Hill, North Carolina) In recent years photo/video sharing web sites like Flickr and YouTube have become increasingly popular. Nowadays, every day terra bytes of photos and videos are uploaded. These data survey large parts of the world throughout the different seasons, various weather conditions and all times of the day. In the talk I will present my work on the highly efficient reconstruction of 3D models from these data. It addresses a variety of the current challenges that have to be addressed to achieve a concurrent 3D model from these data. The challenges are: estimation of the geometric and radiometric camera calibration from videos and photos, efficient robust camera motion estimation for (quasi-)degenerate estimation problems, high performance stereo estimation from multiple views, automatic selection of correct views from noisy image/video collections, image based location recognition for topology detection. In the talk I will discuss the details of our real-time camera motion estimation from video using our Adaptive Real-Time Random Sample Consensus (ARRSAC) and our high performance salient feature tracker, which simultaneously estimates the radiometric camera calibration and tracks the motion of the salient feature points. Furthermore our technique to achieve robustness against (quasi-) degenerate data will be introduced. It allows to detect and overcome the case of data, which under-constrain the camera motion estimation problem. Additionally our optimal stereo technique for determining the scene depths with constant precision throughout the scene volume will be explained during the talk. It allows to perform the scene depth estimation from a large set of views with optimal computational effort while obtaining the depth with constant precision throughout the reconstruction volume. I also discuss our fast technique for the image based location recognition, which uses commodity graphics processors to achieve real-time performance while providing high recognition rates. Furthermore in the talk I present our work on 3D reconstruction from internet photo collections. It combines image based recognition with geometric constraints to efficiently perform the simultaneous selection of correct views and the 3D reconstruction from large collections of photos. The talk will also explain the future challenges in all the mentioned areas. Jan-Michael Frahm is a Research Assistant Professor at University of North Carolina at Chapel Hill. He received his Ph.D in computer vision in 2005 from the Christian-Albrechts University of Kiel, Germany. His Diploma in Computer Science is from the University of Lübeck. Dr.- Ing. Frahm`s research interests include a variety of computer vision problems. He has worked on structure from motion for single/multi-camera systems for static and dynamic scenes to create 3D models of the scene; real-time multi-view stereo to create a dense scene geometry from camera images; use of camera-sensor systems for 3D scene reconstruction with fusion of multiple orthogonal sensors; improved robust and fast estimation methods from noisy data to compensate for highly noisy measurements in various stages of the reconstruction process; high performance feature tracking for salient image-point motion extraction; and the development of data-parallel algorithms for commodity graphics hardware for efficient 3D reconstruction.
May 25, 2009 13:00 Informatikzentrum, Seminarraum G30	Real-time playback and navigation of multi-view video sequences based on space-time tetrahedra Björn Scholz In this diploma thesis, a real-time capable player for free-viewpoint video will be presented. Free-viewpoint video usually consists of huge amounts of video data captured from multiple cameras and additional inter-view and frame information, such as dense correspondence fields between single images or camera positions, to provide smooth navigation. Neither the size nor the representation of the source data is appropriate to be used in such an environment. Thus, besides the player itself, a container combining the data as well as certain compression to reduce its size will be introduced. [pdf der Vortragsfolien]
May 18, 2009 13:00 Informatikzentrum, Seminarraum G30	Moving Gradients: A Path-Based Method for Plausible Image Interpolation Christian Linz We describe a method for plausible interpolation of images, with a wide range of applications like temporal up-sampling for smooth playback of lower frame rate video, smooth view interpolation, and animation of still images. The method is based on the intuitive idea, that a given pixel in the interpolated frames traces out a path in the source images. Therefore, we simply move and copy pixel gradients from the input images along this path. A key innovation is to allow arbitrary (asymmetric) transition points, where the path moves from one image to the other. This flexible transition preserves the frequency content of the originals without ghosting or blurring, and maintains temporal coherence. Perhaps most importantly, our framework makes occlusion handling particularly simple. The transition points allow for matches away from the occluded regions, at any suitable point along the path. Indeed, occlusions do not need to be handled explicitly at all in our initial graph-cut optimization. Moreover, a simple comparison of computed path lengths after the optimization, allows us to robustly identify occluded regions, and compute the most plausible interpolation in those areas. Finally, we show that significant improvements are obtained by moving gradients and using Poisson reconstruction. [pdf der Vortragsfolien] [pdf des Papers]
May 4, 2009 13:00 Informatikzentrum, Seminarraum G30	Best of ICCP 2009 Anita Sellent The first International Conference on Computational Photography (ICCP'09) took place in San Francisco at March 16 th and 17 th. I will give a short overview on the bandwidth of the conference and summarize 2 of the most interesting articles: In "Light Field Superresolution" Bishop et al. show how the trade off between angular and spatial resolution in light field cameras can be mitigated under the assumption of Lambertian scene surfaces. Thus images of surprisingly high resolution can be reconstructed. High Dynamic Range images that are composited of several low dynamic range images usually show ghosting artifacts if objects in the scene move. The article of Gallo et al. about "Artifact-free High Dynamic Range Imaging" describes, how these ghosting artifacts can be totally avoided. [pdf der Vortragsfolien] [MP3 des Vortrags] [pdf Artifact-free High Dynamic Range Imaging] [pdf Light Field Superresolution]
April 27, 2009 13:30 Informatikzentrum, Seminarraum G30	3D Visualisierung der Erdoberfläche im Wandel der Zeitalter (SA) Lorenz Rogge Ziel dieser Studienarbeit ist es, ein Programm zu entwickeln, welches die paläontologische Veränderung des Globus im Laufe der Zeit visualisiert. Basierend auf geologischen Daten und Kartenmaterial soll es möglich sein, die Erdoberfläche zu gewünschten Zeitpunkten annähernd realistisch und in Echtzeit als 3D-Objekt darzustellen. Hierzu müssen die benötigten Daten beschafft und mit einer geeigneten Technologie eingebunden werden. [pdf der Vortragsfolien]
April 20, 2009 10:00 Informatikzentrum, Hörsaal 160	Some thoughts on perceptual realism in computer graphics Philip Dutré (Kath. Universität Leuven, Belgien) One of our research goals is to construct a realism scale, that allows the user to choose the desired level of visual realism in the final image. The higher the realism, the closer the image will appear to look like a photograph. If the user selects a lower realism-level, the gradual decline in realism should appear in the image as smoothly as possible. Preferably, image components that do not contribute to the realistic appearance of the image, should be eliminated from the computations first. Such a realism scale has not yet been constructed in computergraphics. This talk will focus on some of the recent efforts we have pursued in order to construct such a realism scale. Although we are still far away from this goal, we feel that some of the underlying mechanisms and thoughts are useful enough to warrant discussion, and hopefully provide some additional discussion.
April 6, 2009 14:00 Informatikzentrum, Seminarraum G30	Best of Eurographics 2009 Kai Berger and Benjamin Meyer The Eurographics 2009 took place in Munic, from 30th of march to 3rd of april. We will present some of its highlights and summarize the most important proceedings from the different topics. [pdf der Vortragsfolien]
April 6, 2009 13:00 Informatikzentrum, Seminarraum G30	Enhancing and Experiencing Spacetime Resolution with Videos and Stills Martin Eisemann An algorithm by A. Gupta will be presented for enhancing the spatial and/or temporal resolution of videos. It targets the emerging consumer-level hybrid cameras that can simultaneously capture video and high-resolution stills. The technique produces a high spacetime resolution video using the high-resolution stills for rendering and the low-resolution video to guide the reconstruction and the rendering process. The presented framework integrates and extends two existing algorithms, namely a high-quality optical flow algorithm and a high-quality image-based-rendering algorithm. The framework enables a variety of applications that were previously unavailable to the amateur user, such as the ability to (1) automatically create videos with high spatiotemporal resolution, and (2) shift a high-resolution still to nearby points in time to better capture a missed event. [pdf der Vortragsfolien] [pdf des Papers] [mp3 des Vortrages]
March 23, 2009 13:00 Informatikzentrum, Hörsaal 160	Multi-view Reconstruction of Detailed Garment Motion Derek Bradley (Univ. British Columbia, Canada) A lot of research has recently focused on the problem of capturing the geometry and motion of garments. Such work usually relies on special markers printed on the fabric to establish temporally coherent correspondences between points on the garment's surface at different times. Unfortunately, this approach is tedious and prevents the capture of off-the-shelf clothing made from interesting fabrics. In this talk I will summarize recent advances in detailed, marker-free garment capture resulting from our research at the University of British Columbia. I will first discuss our physical acquisition setup, including camera synchronization and rolling shutter compensation using stroboscopic illumination. I will then describe our garment capture approach, where we establish temporally coherent parameterizations between incomplete geometries that we extract at each timestep with a multiview stereo algorithm. Finally, I will discuss a method for reintroducing fine folds into the captured models using data-driven dynamic wrinkling. As a result of this work, we are able to capture the geometry and motion of unpatterned, off-the-shelf garments made from a range of different fabrics, with realistic dynamic folds. [pdf des Papers]
March 16, 2009 13:00 Informatikzentrum, Seminarraum G30	Graph-Theoretic Scagnostics Georgia Albuquerque Graph-Theoretic Scagnostics was presented in the IFOVIS 2005 and proposes different quality measurements for scatterplots. The proposed quality measures are based on an exploratory visualization method developed by John and Paul Tukey around 20 years ago, called Scagnostics. [pdf der Vortragsfolien] [pdf des Papers]
March 9, 2009 13:00 Informatikzentrum, Seminarraum G30	Lunar Surface Reconstruction from Single Images Stephan Wenger For the planned Lunar Obervation Center and Islamic Museum in Mekka, Saudi-Arabia, a 3-meter-sized moon globe with realistic surface relief is to be created. Since the resolution of directly measured height maps is about a factor of ten too low for that purpose, the missing detail has to be plausibly (but not necessarily exactly) estimated from photographic images at heigher resolution. Usual shape- from-shading approaches fail because most moon regions have only be photographed in detail at a single light condition. Our heuristic algorithm nevertheless finds plausible surface normals that are integrated to yield a detailed height map of the whole moon. [pdf der Vortragsfolien] [mp3 des Vortrages]
March 6, 2009 13:00 Informatikzentrum, Seminarraum G30	Image-based Viewpoint Navigation through space and time Christian Lipski We present an image-based rendering system to viewpoint-navigate through space and time of complex real-world, dynamic scenes. Our approach accepts unsynchronized, uncalibrated multi-video footage as input. Inexpensive, consumer-grade camcorders suffice to acquire arbitrary scenes, e.g., in the outdoors, without elaborate recording setup procedures. Instead of scene depth estimation, layer segmentation, or 3D reconstruction, our approach is based on dense image correspondences, treating view interpolation uniformly in space and time: spatial viewpoint navigation, slow motion, and freeze-and-rotate effects can all be created in the same way. Acquisition simplification, generalization to difficult scenes, and space-time symmetric interpolation [pdf der Vortragsfolien] [mp3 des Vortrages]
March 2, 2009 13:00 Informatikzentrum, Seminarraum G30	Image/Video error metrics Kai Berger When the subjective quality of e.g. compressed image or video data is to be approximated by an objective metric, popular formulae such as MSE or PSNR appear to do the job well. However, in several scenarios these standard formulae don't correspond subjective quality evaluations. In this talk three different types of image/video quality assessment methods are presented. Exemplaric algorithms for these types will be compared to MSE/PSNR. [pdf der Vortragsfolien] [mp3 des Vortrages] [pdf des Papers]
February 23, 2009 13:00 Informatikzentrum, Seminarraum G30	Multi-View Stereo algorithms - overview and comparison Christian Lipski Multi-View Stereo reconstruction algorithms are a very active field in computer graphics and computer vision. Seitz et al. have established multi-view data sets with known ground truth as a basis for evaluation and comparison (http://vision.middlebury.edu/mview/). We took a closer look at the current top performers, evaluate approaches with our own data sets and identify cases where these approaches fail. Possible solutions are presented and discussed. [pdf der Vortragsfolien] [Website Multi-View Stereo Evaluation]
February 16, 2009 13:00 Informatikzentrum, Seminarraum G30	Space-time Surface Reconstruction Using Incompressible Flow Christian Linz We introduce a volumetric space-time technique for the reconstruction of moving and deforming objects from point data. The output of our method is a four-dimensional generalized cylinder in space-time, made up of spatial slices, each of which is a three-dimensional solid bounded by a watertight manifold. The motion of the object is described as an incompressible flow of material through time. We optimize the flow so that the distance material moves from one time frame to the next is bounded, the density of material remains constant, and the object remains compact. This formulation overcomes deficiencies in the acquired data, such as persistent occlusions, errors, and missing frames. We demonstrate the performance of our flow-based technique by reconstructing coherent sequences of watertight models from incomplete scanner data. [pdf der Vortragsfolien] [pdf des Papers]
February 6, 2009 13:00 Informatikzentrum, Seminarraum G30	Pixel-exact shadow-mapping based on GPU ray tracing using CUDA Rolf Krämer Die stetig fortschreitende Entwicklung von Grafikkarten Prozessoren (GPUs) eröffnen neue Möglichkeiten die Standard-Grafikpipeline zu durchbrechen und generellere Konzepte auf der GPU umzusetzen (GPGPU). Gerade auch in der gängigen Grafikdarstellung mittels Rasterisierung ist die Erweiterung sinnvoll, da man in vielen Bereichen an seine Grenzen gestossen zu sein scheint. Ein Beispiel dafür ist die Darstellung von harten Schatten. Gängige echtzeitfähige Ansätze wie ShadowMaps können für Aliasing-Artefakte an den Schattenkanten sorgen, welche unangenehm auffallen. In dieser Arbeit wurde ein Hybrid-System entworfen, welches diese Nachteile umgeht und pixelgenaue Schatten berechnet. Dafür werden die Primärstrahlen und das Shading mittels gewöhnlicher Standardpipeline berechnet, während die Schatten durch einen GPU-unterstützten Ray Tracer berechnet werden, welcher unter Zuhilfenahme von NVidias CUDA entworfen wurde.
January 30, 2009 13:00 Informatikzentrum, Hörsaal 160	Unterstützung der visuellen Analyse hochdimensionaler Daten durch klassenbasierte Projektionsgütemas Andrada Tatu Zunehmende Dimensionalität und anwachsendes Datenvolumen erfordern effektive Explorationstechniken, um dem Benutzer Einblicke in Muster in den Daten zu ermöglichen. Bei der visuellen Analyse müssen dabei hochdimensionale Daten auf niedrigdimensionale Sichten projiziert werden. Es gibt verschiedene Ansätze um niedrigdimensionale Darstellungen aus hochdimensionalen Daten zu erzeugen und diese zu bewerten. In dieser Arbeit werden Verfahren vorgestellt um gute Projektionen hochdimensionaler Daten zu erhalten. Es werden dazu Konzepte präsentiert um lineare und nichtlineare Projektionen zu finden, die an realen Daten getestet werden. Kern der Arbeit ist dabei mit Hilfe von achsenparallelen und nicht-achsenparallelen Projektionen Dimensionen und Unterräume der Daten zu finden, die die Datenstruktur am besten darstellen. Zur Bewertung der Projektionen werden Projektionsgütemasse vorgestellt, welche im Gegensatz zu existierenden Verfahren die Dichteverteilung der Daten berücksichtigen. Vorteil dieser Methode ist es, dass nicht nur Beziehungen zwischen zwei Dimensionen, sondern auch zwischen mehreren Dimensionen gefunden werden.
January 26, 2009 14:00 Informatikzentrum, Seminarraum G30	Computational Vision for Graphics Oliver Grau (BBC Research & Development, London)
January 26, 2009 13:00 Informatikzentrum, Seminarraum G30	Imperfect Shadow Maps for Efficient Computation of Indirect Illumination Benjamin Meyer We present a method for interactive computation of indirect illumination in large and fully dynamic scenes based on approximate visibility queries. While the high-frequency nature of direct lighting requires accurate visibility, indirect illumination mostly consists of smooth gradations, which tend to mask errors due to incorrect visibility. We exploit this by approximating visibility for indirect illumination with imperfect shadow maps - low-resolution shadow maps rendered from a crude point-based representation of the scene. These are used in conjunction with a global illumination algorithm based on virtual point lights enabling indirect illumination of dynamic scenes at real-time frame rates. We demonstrate that imperfect shadow maps are a valid approximation to visibility, which makes the simulation of global illumination an order of magnitude faster than using accurate visibility. [pdf der Vortragsfolien] [pdf des Papers]
January 12, 2009 13:00 Informatikzentrum, Seminarraum G30	Unwrap Mosaics: a new representation for video editing Anita Sellent Though photoediting is very common today, extending such editing task on video is still very tedious work. In their SIGGRAPH 2008 paper Rav-Acha et al. present a new way to edit uncalibrated monocular video footage. The basic idea of the approach is to represent a video sequence as a 2D mosaic accompanied by a mapping from the mosaic to the frames of the video and an occlusion map. Editing operations can than be performed directly on the mosaic and resomposited with the original video. In this colloquium, ideas and details necessary for the determination of the mosaic, mapping and occlusion map are disscussed. [pdf der Vortragsfolien]
December 15, 2008 13:30 Informatikzentrum, Seminarraum G30	Tomographic Reconstruction of Gas Flows in the Presence of Occluders Kai Berger Nowadays, non-stationary and time-varying gas flows, for example the heated air above a camping stove, can be captured and tomographically reconstructed by making use of the Background-oriented Schlieren (BOS) method. In this method a high-frequency noise pattern, for example generated by wavelet noise, is placed behind the volume under observation and the per pixel deflections in the input image caused by the varying refractive index of the gas volume is measured. These deflections, which can be computed by optical flow methods, can be integrated to a tomographically consistent refractional index volume by solving an equation system for 3D deflection vectors and integrating them, e.g. by a Poisson-integration. However, when the interaction of such a gas with occluding objects is examined, for example when a marshmellow is moved above the camping stove, different alterations to the existing tomographic reconstruction algorithm have to be applied. In this talk the existing method is introduced and the occuring problems with occluding objects are stated. Afterwards, alterations to the stages of this method are proposed and evaluated. [pdf der Vortragsfolien]
December 5, 2008 14:00 Informatikzentrum, Seminarraum G30	The OMNI Display: Using a Large Peripheral Display for Workgroup Awareness in Distributed Groups Maryam Mustafa The initiation of interaction in face-to-face work environments is a gradual process and takes place in a rich information landscape of awareness and social signals. This gradual approach to interaction is missing from most online messaging systems. In this talk I will be discussing a prototype system called the Open Messenger Notification and Interaction (OMNI) display that uses a projected peripheral display to provide dynamic, real-time awareness information using a peripheral display in the architectural space of the user in ways that are both rich and subtle. OMNI has been designed to use people's natural abilities to absorb information in the periphery without being distracted from their primary task. OMNI accomplishes this by using motion and color to subtly provide several types of information about online contacts. I will discuss our approach to capturing and presenting relevant information for awareness of the surroundings, facilitating interaction and creating an online collaborative environment.
December 5, 2008 13:00 Informatikzentrum, Seminarraum G30	Exhaustive visual search for information in multi-dimensional data-sets Georgia Albuquerque and Martin Eisemann Goal of this research project is to develop and evaluate a fundamentally new approach to exhaustively search for, and interactively characterize any non-random mutual relationship between attribute dimensions in general data sets. To be able to systematically consider all possible attribute combinations, we propose to apply image analysis to visualization results in order to automatically pre-select only those attribute combinations featuring non-random relationships. To characterize the found information and to build mathematical descriptions, we rely on interactive visual inspection and visualization-assisted interactive information modeling. This way, we intend to discover and explicitly characterize all information implicitly represented in unbiased sets of multi-dimensional data points. [pdf der Vortragsfolien]
November 3, 2008 17:00 Informatikzentrum, Hörsaal 160	Shape, neue 3D Methoden für astrophysikalische Modelle Wolfgang Steffen Für die meisten Fragen waren astrophysikalische 3D Simulationen mit angemessener Auslösung bis vor einigen Jahren zu aufwendig. Andererseits hat sich von der Beobachtungsseite her in den letzten Jahrzehnten klar gezeigt, dass die Struktur vieler astrophysikalischer Objekte intrinsisch 3D ist. Wie diese Formen zustande kommen scheint tief in der offensichtlich nur teilweise verstandenen Entwicklungsgeschichte der Objekte zu stecken. Dies gilt insbesondere für planetarische Nebel, ein Entwicklungsstadium für sonnenähnliche Sterne. Die Notwendigkeit, die 3D-Struktur dieser Nebel zu kennen, hat uns dazu verleitet, ein neues Konzept der Strukturmodellierung in die Astrophysik einzuführen: Interaktives Modellieren, wie es in der Graphikindustrie üblich ist, mit dem Extra der Geschwindigkeit als wissenschaftliche Diagnostik. "Shape" ist das Ergebnis dieser Entwicklung und ist bisher das einzige Programmpaket seiner Art.
October 22, 2008 13:00 Informatikzentrum, Seminarraum G30	Motion Effects - Bewegungseffekte in Bildern und Videos Martin Fiebig "Ein Bild sagt mehr als 1000 Worte". Um die Aussage eines Bildes noch weiter hervorzuheben, ist es oft hilfreich nicht photorealistische (NPR) Effekte zu verwenden (wie z.B. Speedlines). In diesem Vortrag wird vorgestellt, wie mit dem bestehenden Interpolationsverfahren des CG-Instituts nicht photorealistische Effekte erzeugt werden können. Es werden verschiedene Algorithmen und Verfahren präsentiert.
October 22, 2008 13:00 Informatikzentrum, Seminarraum G30	Korrektur des zeitlichen Versatzes zwischen mehreren unsynchronisierten Videosequenzen einer dynamis Markus Lorenz Wird eine dynamische Szene zeitgleich mit mehreren Kameras gefilmt, sind die Videosequenzen meist asynchron. Dies resultiert aus einem zeitversetzten Aufnahmestart. Für viele moderne Verfahren der Computergraphik ist jedoch unabdingbar, diesen Zeitversatz auf einfache Art und Weise bestimmen zu können. In diesem Vortrag wird die Umsetzung von Algorithmen zur Versatzbestimmung vorgestellt.
September 4, 2008 14:00 Informatikzentrum, Seminarraum G30	SIMD-Raytracing with the Single Slab Hierarchy Christian Woizischke During the last years ray tracing became more and more important again in the field of computer graphics. Faster algorithms, better data structures and faster PCs allow for interactive or even real-time ray tracing. The biggest gain in speed is achieved due to acceleration data structures such as Bounding Volume Hierarchies (BVH) or kd-Trees. In this talk a new acceleration data structure is presented, the Single Slab Hierarchy. The Single Slab Hierarchy is similar to a BVH but represents every node with just one slab. Even though information is lost due to this, one can calculate a conservative hit/miss with a ray, using an active ray interval. This has several benefits. First, traversal becomes very similar to kd-Trees and memory requirements are reduced to 25 percent compared to a standard BVH, which is very beneficial if complex models are to be rendered.
April 1, 2008 15:00 Informatikzentrum, Hörsaal 160	Astrophysical gaseous nebulae: 1D and 3D models Christophe Morisset The interstellar medium is the counterpart of the stars in the cycle of matter evolution in the Universe. New stars are build from giant gaseous clouds and dead stars are giving back to the interstellar medium new elements synthesized during their life. Understanding the physics of such gaseous nebulae is a key to our knowledge of the chemical evolution of our Universe. I will present in this talk the computational tools used to model such gaseous nebulae, especially the 3D photoionization codes, and some applications to HII regions and Planetary Nebulae.
December 19, 2007 17:00 Aula, Haus der Wissenschaft	Computer - Bilder Marcus Magnor Antrittsvorlesung Prof. Marcus Magnor.
May 15, 2007 15:00 Informatikzentrum, Hörsaal 160	Perceptual Graphics: The Integration of Perception Research and Computer Graphics Research Douglas Cunningham Real visual scenes specify an enormous amount of perceptually and behaviorally relevant information. Perception science investigates how the sensory systems of humans and animals extract, represent, and process such information. Computer graphics focuses on the visual simulation of such information, traditionally emphasizing a high degree of realism. Although these two fields have developed independently, they address similar fundamental problems and provide complementary methods for their solution. Furthermore, it is becoming increasingly apparent that specific research questions in either discipline cannot be solved without methods from the other. The fusion of these two complementary approaches not only helps to overcome the inherent limits of each approach, but also opens up entire new realms of scientific inquiry. This integrated approach is referred to as Perceptual Graphics. In this talk, I will provide an overview of how perception and computer graphics can help one another, both symbiotically and in a truly integrated fashion. I will also provide a brief look at several examples of current Perceptual Graphics research.
March 6, 2007 14:00 Informatikzentrum, Seminarraum G30	High Dynamic Range Imaging and Display Wolfgang Heidrich The human visual system's ability to process wide ranges of intensities by far exceeds the capabilities of current imaging systems. Both cameras and displays are currently limited to a dynamic range (contrast) of between 300:1 to 1,000:1, while the human visual system can process a simultaneous dynamic range of 50,000:1 or more, and can adapt to a much larger range. High-dynamic-range (HDR) imaging refers to the capture, processing, storage, and display of images with significantly improved contrast and brightness compared to the conventional imaging pipeline. This new HDR imaging pipeline is designed to match the power of the human visual system. HDR displays significantly improve the sense of realism and immersion when showing both real and synthetic HDR imagery. Likewise, HDR cameras are able to take images without saturation under difficult lighting situations. The additional information captured in both extremely bright and extremely dark regions is useful as an input for HDR displays, but also for machine vision applications. In this talk, I will summarize the results of a multi-disciplinary research effort to create the first true HDR display. This work is a collaboration of multiple departments at The University of British Columbia, and a spin-off company called Brightside Technologies. I will provide an overview of current research activities, with a focus on computational problems.
December 22, 2006 11:00 Informatikzentrum, Seminarraum G30	Eikonal Rendering Ivo Ihrke In this talk, I present an interactive rendering method for refractive objects. The refractive index is allowed to vary continouosly, and total reflection is taken into account. The method is based on set of ordinary differential equations that are derived from the eikonal equation, the main postulate of ray optics. This set of equation allows for ray casting of bent light rays with the complexity of a particle tracer.
October 19, 2006 13:00 Informatikzentrum, Seminarraum G30	A Framework for Holographic Scene Representation Remo Ziegler (ETH Zürich) At ETH we developed a framework for holographic representation and display of graphics objects. As opposed to traditional graphics representations, our approach reconstructs the light wave reflected or emitted by the original object directly from the underlying digital hologram. Our novel holographic graphics pipeline consists of several stages including the digital recording of a full-parallax hologram, the reconstruction and propagation of its wavefront, and rendering of the final image onto conventional, framebuffer-based displays. The required view-dependent depth image is computed from the phase information inherently represented in the complex-valued wavefront. Our model also comprises a correct physical modelling of the camera taking into account optical elements, such as lens and aperture. It thus allows for a variety of effects including depth of field, diffraction, interference and features built-in anti-aliasing. A central feature of our framework is its seamless integration into conventional rendering and display technology, which enables us to elegantly combine traditional 3D object or scene representations with holograms.
August 22, 2006 14:00 Informatikzentrum, Seminarraum G30	Gaussian curvature on polyhedral surfaces Anita Sellent The Gaussian curvature of a regular surface is a well-known term in differential geometry; there are even several equivalent ways to define it. Gauss himself defined this curvature via the normal image. In the presentation this definition is transferred to polyhedral surfaces: Though the procedure is obvious for convex vertices it causes some difficulties for non-convex vertices. A method to calculate the normal image for some of the non-convex vertices is presented which on the one hand confirms the angle-deficit as polyhedral Gaussian curvature and on the other hand bears further information on the vertices. In conclusion some of the fundamental theorems for the continuous Gaussian curvature can be affirmed for its polyhedral analogue.
July 18, 2006 14:00 Informatikzentrum, Seminarraum G30	Boosting Restricted to Integer Lattices Dirk Breitenreicher (Universität Mannheim) When classifying a set of samples into various classes in most cases one highly complex optimization problem has to be solved. A boosting approach, in contrast, is able to determine multiple weak learners such that their combination is as accurate as the single, strong classification rule. Often these weak learners are easier to obtain than the solution of the complex optimization problem. However, finding weak learners that can be used for boosting is a not trivial task. Obtaining multiple weak learning rules may also require a lot of time and memory. Classifying on integer lattices can address this problem. When using classifiers on integer lattices each weak learner is build up on integer variables exclusively. This causes that the training and the evaluation time as well as the required memory decreases dramatically in most cases.
April 26, 2006 14:00 Informatikzentrum, Seminarraum G30	Automatic Creation of Object Hierachies for Ray tracing of Dynamic Scenes Martin Eisemann Ray tracing acceleration techniques most often consider only static scenes, neglecting the processing time needed to build the acceleration data structure. With the development of interactive ray tracing systems, this reconstruction time becomes serious bottleneck if concerned with dynamic scenes. I am going to describe two strategies for efficient updating of bounding volume hierarchies (BHV) for scenarios with arbitrarily moving objects. The first exploits spatial locality in the object distribution for faster reinsertion of the moved objects. The second allows insertion and deletion of objects at almost constant time by using a hybrid system, which combines benefits from both spatial subdivision and BHVs. Depending on the number of moving objects, the algorithms adjust a dynamic BHV six to one hundred times faster than it would take to rebuild the complete hierarchy, while rendering times of the resulting hierarchy remains almost untouched.

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TU Braunschweig - Fakultät für Mathematik und Informatik - Computer Graphics - Talks