Events
Talk Fast image reconstruction for Magnetic-Particle-Imaging by Chebyshev Transformations
08.08.2016 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Leonard Schmiester
Image reconstruction in magnetic-particle-imaging (MPI) is done using an algebraic approach for Lissajous type measurement sequences. By solving a large linear system of equations the spatial distribution of magnetic nanoparticles can be determined. Despite the use of iterative solvers that converge rapidly, the size of the MPI system matrix leads to reconstruction times that are typically much longer than the actual data acquisition time. For this reason, matrix compression techniques have been introduced that transform the MPI system matrix into a sparse domain and then utilize this sparsity for accelerated reconstruction. Within this scope we investigate the Chebyshev transformation for matrix compression. By reducing the number of coefficients per matrix row to one, it is even possible to derive a direct reconstruction method that circumvents the usage of iterative solvers.
Talk MA-Talk: Guided Camera Placement for Image-Based Rendering
11.07.2016 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Leslie Wöhler
Talk Promotions-V-Vg: Gaze-Contingent Perceptual Rendering in Computer Graphics
01.07.2016 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Michael Stengel
Contemporary digital displays feature multi-million pixels at ever-increasing refresh rates. Reality, on the other hand, provides us with a view of the world that is continuous in space and in time. The discrepancy between viewing the physical world and its sampled depiction on digital displays gives rise to perceptual quality degradation. By measuring or estimating where we look, gaze-contingent algorithms aim at exploiting the way we visually perceive to remedy visible artifacts. In his dissertation pre-talk Michael Stengel will present recent results from projects in the field of gaze-contingent and perceptual algorithms. Two projects aim at boosting the perceived visual quality of conventional video footage when viewed on commodity monitors or projection. In addition he will describe a novel head-mounted display with real-time gaze tracking resulting in many novel applications in the context of Virtual Reality and Augmented Reality. In a follow-up project Michael and colleagues derived a novel gaze-contingent render method using active gaze tracking to reduce computational efforts when shading virtual worlds.
Talk Promotions-V-Vg: Reconstruction, Analysis and Editing of Dynamically Deforming 3D Surfaces
10.06.2016 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Thomas Neumann
Dynamically deforming 3D surfaces play a major role in computer graphics. However, producing time-varying dynamic geometry at ever increasing detail is a labor-intensive process, and so a recent trend is to capture geometry data directly from the real world. The first part of this talk presents novel approaches in this direction, approaches that capture dense dynamic 3D surfaces from multi-camera systems in a particularly robust and accurate way. This provides highly realistic dynamic surface models for phenomena like moving garments and bulging muscles.
However, conveniently re-using, editing or otherwise analyzing dynamic 3D surface data is not yet possible. The second part of the talk thus deals with novel data-driven modeling and animation approaches. I first show a supervised data-driven approach for modeling human muscle deformations, an approach that scales to huge datasets and provides fine-scale, anatomically realistic deformations at a high quality not shown by previous data-driven methods. I then extend data-driven modeling to the unsupervised setting, thus providing editing tools for a wider set of input data ranging from facial performance captures and full body motion to muscle and cloth deformations. To this end, I introduce the concepts of sparsity and locality within a mathematical optimization framework. I also explore these concepts for constructing shape-aware functions that are useful for static geometry processing, registration and localized editing.
Talk MA-Talk: Interactive Realtime Image Segmentation
29.04.2016 11:00
Informatikzentrum, Seminarraum G30
Speaker(s): Moritz Mühlhausen
Talk New Technologies driving Visual Computing Research
27.04.2016 14:30
Hochschule Bonn-Rhein-Sieg
Speaker(s): Marcus Magnor
Recent developments in consumer electronics have a profound impact even on fundamental research agendas and conference programs in visual computing. Programmable GPUs, 3D movies, Kinect, HDR displays, 4k video projectors, Oculus Rift, or all-in-one smartphones are just a few examples of how sudden, widespread availability and adoption of “new” technologies drive contemporary research (even though most of it had, in fact, already been available in the lab for quite some time). In my talk, I will concentrate on a few ongoing consumer technology trends and demonstrate how they are triggering intriguing new research in visual computing.
Talk MA-Talk: Globally Weighted 3D Reconstruction with Accurate Visibility Computation
25.04.2016 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Marc Kassubeck
Talk Image-based Methods to Measuring and Modeling Flow Phenomena of Gases and Liquids
14.04.2016 10:00
Honolulu, USA
Speaker(s): Marcus Magnor
invited plenary speaker at ISIMet 2016 (abstract)
Talk Teamprojekt-Abschluss: Real-time Augmented Reality Hologram
12.02.2016 14:15
Informatikzentrum, Seminarraum G30
Präsentation der Ergebnisse des studentischen Teamprojekts.
Talk Context-aware dynamic Sensor Fusion
28.09.2015 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Thiemo Alldieck
Sensor fusion aims to compensate for individual strengths and weaknesses of different sensors. When recording a complex scene over a longer period, these characteristics might change, resulting in possible system instabilities. The presented work introduces a new dynamic method for data fusion of different imaging devices, namely RGB and thermal camera. Therefor background conformity values of two image sources are fused in order to enable stable background subtraction for persistent surveillance. Image quality heuristics based on image characteristics and contextual information are specified to evaluate the usefulness of the modalities and perform the fusion context aware.
Talk Three Geometric Structures and their Applications
18.09.2015 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Nabil Mustafa
Since the beginning of systematic research on geometric computing almost forty years ago, there has been a very fruitful interplay between the mathematical study of geometric structures and the search for efficient and practical solutions for a variety of problems involving geometric data. In this talk I will illustrate this with applications to three different areas: computer graphics, algorithms and combinatorics.
Talk Disputation
07.08.2015 10:00
Informatikzentrum, IZ 161
Speaker(s): Pablo Bauszat
Advanced Denoising and Memoryless Acceleration for Realistic Image Synthesis
Talk Disputation
27.07.2015 14:00
Informatikzentrum, Seminarraum G04
Speaker(s): Benjamin Meyer
Measuring, modeling and simulating the re-adaptation process of the Human Visual System after short-time glares in traffic scenarios
Talk Disputation
17.07.2015 15:00
Informatikzentrum, IZ 161
Speaker(s): Kai Ruhl
Interactive Spacetime Reconstruction in Computer Graphics
Talk Disputation
13.07.2015 13:15
Informatikzentrum, Seminarraum G04
Speaker(s): Maryam Mustafa
ElectroEncephaloGraphics - a Novel Modality for Graphics Research
Talk Disputation
03.07.2015 10:00
Informatikzentrum, Seminarraum G04
Speaker(s): Lorenz Rogge
Augmenting People in Monocular Video Data
Talk Methods for Analyzing the Influence of Molecular Dynamics on Neuronal Activity
26.06.2015 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Stefan Sokoll
Investigating the functioning of neurons at the molecular level is an important foundation to understand how higher brain functions like perception, behavior, or learning and memory are accomplished. Since molecular processes occur in the nanometer range and have to be studied in living samples, recently developed optical super-resolution techniques have boosted their characterization. However, super-resolution techniques require complex instrumentation, are hardly applicable to organotypic samples and still suffer from relatively low temporal resolution. This talk presents new analysis tools that aim to overcome these limitations and allow to study how the dynamics and the interplay of molecules modulate synaptic transmission efficiency. At first, an approach for the detection of individual presynaptic activity will be briefly introduced, but the major part focuses on an algorithm that facilitates fast 3D molecular dynamic analyses within brain slices. It adjusts astigmatism-based 3D single-particle tracking (SPT) techniques to depth-dependent optical aberrations induced by the refractive index mismatch so that they are applicable to complex samples. In contrast to existing techniques, the presented online calibration method determines the aberration directly from the acquired 2D image stream by exploiting the inherent particle movement and the redundancy introduced by the astigmatism. The method improves the positioning by reducing the systematic errors introduced by the aberrations and allows to correctly derive the cellular morphology and molecular diffusion parameters in 3D independently of the imaging depth.
Talk Promotions-V-Vg: Real-World Video Processing Using Unstructured Scene Representations
26.06.2015 10:00
Informatikzentrum, Seminarraum G30
Speaker(s): Felix Klose
When processing single or multi-view video data recorded in uncontrolled environments using scene reconstruction algorithms a multitude of factors can negatively influence the result quality. These factors include camera, lens or color miscalibrations, errors in temporal or spatial camera alignment, unsynchronized and rolling shutters on the camera side, as well as specular, untextured, repetitive objects or objects with visually complex appearances inside the scene. These circumstances make working with computer vision algorithms on real-world data a very challenging task and errors in measurements in real-world recoding setups can not be avoided and have to be accounted for.
In this talk I will give an overview of my work in single and multi-view video processing of real world data using unstructured scene representations. I show how dense 2D correspondence based stereoscopic free-viewpoint video can be created, using tools for user guided error correction. How the complexity of real-world multi-view data can be handled by tracking small surface patches and using a strict motion model to resolve ambiguities and create quasi dense scene
representations. And finally how to create high quality video effects that can handle extreme amounts of noise in estimated depth maps by leveraging the redundancy inherent in video data.
Talk Bild-Aspekte
15.06.2015 17:00
Braunschweigische Wissenschaftliche Gesellschaft
Speaker(s): Marcus Magnor
plenary talk
Bilder sind ein faszinierendes Phänomen der Natur. Jeder selbst leuchtende und jeder beleuchtete Gegenstand sendet ununterbrochen und in alle Richtungen Bilder aus, die Auskunft über ihren Ursprungsort und ihre Entstehung geben. Bilder breiten sich im freien Raum ungehindert aus, sie konservieren Information über Raum und Zeit hinweg und transportieren sie mitunter Milliarden Lichtjahre weit. Bilder sind universell. Mit unserem Sehsinn empfangen wir einen (sehr kleinen) Teil der Bilder, die die Natur ununterbrochen aussendet. Ohne Zeitverzögerung informieren sie uns uber unsere nähere und weitere Umgebung. Auf Basis von Bildern lernen wir unsere Welt kennen, verstehen und auf sie zu reagieren.
Talk MA-Talk: Compressed Sensing-based Progressive Reconstruction for Image Synthesis
11.05.2015 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Cong Wang
Compressed Sensing (CS) is a new mathematical framework for reconstruction of signals with missing information. Recently, its application to sparse image reconstruction, reconstruction of an image from a small set of known pixels, has shown promising results. The key idea is derived from the fact that most natural images are highly compressible because they are sparse in a transform domain. This leads to the obvious questions: Why waste resources on evaluating information (here, individual pixels) that are discarded later on or have only small impact on the overall visual impression? So far the measurements (evaluated pixels of the image) are chosen in random fashion (usually based on a Blue Noise distribution) to uniformly cover the image domain. Theoretically, if salient features of the image are known in advance, fewer measurements would be needed for high-quality reconstruction. For real-world images taken by a photo or video camera it is very hard to evaluate important features of the image without actually capturing them. However, during image synthesis more knowledge about the scene, camera and lighting situation is present. If carefully observed, the rendering process can potentially provide useful cues which are more efficient to evaluate than the actual measurements, can guide the image sampling process, and thus accelerate convergence.
Talk BA Talk: Tiefenbasierte Blickpunktgenerierung für interaktive Videos in immersiven VR-Systemen
27.04.2015 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Inga Menke
Virtual Reality Head-mounted Displays ermöglichen bei der Betrachtung von Bildern und Videos den Sprung von der traditionellen Fenster-Metapher hin zum virtuellen Rundum-Blick des Betrachters. Die Kombination aus Panoramavideo und Virtual Reality Display mit Head-Tracking schaffen die Voraussetzungen für die die freie Wahl der Blickrichtung auf die Inhalte. Die im Vortrag präsentierte Bachelorarbeit betrachtet für die Entwicklung immersiver medialer Inhalte den nächsten logischen Schritt : Ein Verfahren für die freie Wahl der Betrachterposition in der dargestellten Szene. Präziser wird es dem Betrachter ermöglicht, bei Positionsänderung des Kopfes die Bewegungsparallaxe innerhalb des Videos wahrzunehmen. Durch die Möglichkeit der Bewegung wird der Immersionsgrad im Video erhöht.
Talk Promotions-V-Vg: Electroencephalographics:A Novel Modality for Graphics Research
24.04.2015 11:00
Informatikzentrum, Seminarraum G30
Speaker(s): Maryam Mustafa
In this thesis I present the application of ElectroEncephaloGraphy(EEG) as a novel modality for investigating perceptual graphics problems.
Until recently, EEG has predominantly been used for clinical diagnosis, in psychology and by the BCI community. Here I extend its scope to assist in understanding the perception of visual output from graphics applications and to create new methods based on direct neural feedback.
My work uses EEG data to determine the perceptual quality of videos and images which is of paramount importance for most graphics algorithms. This is especially important given the gap between perceived quality of an image and physical accuracy.
One of the main impediments to the use of an EEG is the very low Signal-to-Noise Ratio (SNR) which requires averaging the data from many trials and participants to get a meaningful result. I propose a novel method for evaluating EEG signals which allows prediction of perceived image quality from only a single trial.
This thesis also explores the possibilities for automatic optimization of rendering parameters for images and videos based on implicit neural feedback.
Talk User-guided Image Pre-Segmentation
17.04.2015 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Ying Wang
This is the presentation of a specialisation project done at the Institut für Computergraphik. The student shows a method for computing a locally linear image structure which is then used to propagate user input in the form of brush strokes in the image at hand. The talk includes some aspect of the numerical computation done in MATLAB and presents a variety of results.
Talk Promotions-V-Vg: Interactive Scene Reconstruction and Image Correspondence Estimation
10.04.2015 13:00
Informatikzentrum, Seminarraum G30
Speaker(s): Kai Ruhl
High-quality dense correspondence maps between images and scene reconstruction, be it optical flow, stereo or scene flow, are an essential prerequisite for a multitude of computer vision and graphics tasks, e.g. scene editing or view interpolation in visual media production. Due to the ill-posed nature of the estimation problem in typical setups (i.e. limited amount of cameras and limited frame rate), automated estimation approaches are prone to erroneous correspondences and subsequent quality degradation in many non-trivial cases such as occlusions, ambiguous movements, long displacements, or low texture. While improving estimation algorithms is one possible direction, this thesis complementarily concerns itself with minimal user interactions that lead to improved correspondence maps and scene reconstruction. Where visually convincing results are essential, rendering artifacts resulting from estimation errors are usually repaired by hand with image editing tools, which is time consuming and therefore costly. New forms of user interaction that integrate human scene recognition capabilities to guide a semi-automatic correspondence or scene reconstruction algorithm have the potential to save considerable effort, enabling faster and more efficient production of visually convincing rendered footage.
Talk Promotions-V-Vg: Advanced Denoising and Memory-efficient Acceleration for Realistic Image Synthesis
06.03.2015 11:00
Informatikzentrum, Seminarraum G30
Speaker(s): Pablo Bauszat
Stochastic ray tracing methods have become the industry's standard for today's realistic image synthesis thanks to their ability to achieve a supreme degree of realism by physically simulating various natural phenomena of light and cameras (e.g. global illumination, depth-of-field or motion blur). Unfortunately, high computational costs for more complex scenes and image noise from insufficient simulations are major issues of these methods and, hence, acceleration and denoising are key components in stochastic ray tracing systems. In this thesis, we introduce three new filtering methods for advanced lighting and camera effects, as well as two new concepts for memory-efficient acceleration structures. In particular, we present a filter for global illumination aiming at real-time performance, an interactive filter for global illumination in the presence of depth-of-field and a general and robust adaptive reconstruction framework for high-quality images with arbitrary rendering effects. To address complex scene geometry, we propose an extension to the classic Bounding Volume Hierarchy reducing its footprint down to 1 bit per node and a new concept which models the acceleration structure completely implicit, i.e. without any additional memory cost at all, while maintaining interactive performance. Our contributions advances the state-of-the-art of denoising techniques for realistic image synthesis as well as the field of memory-efficient acceleration for ray tracing systems.