%0 Conference Paper
%D 2007
%T Usability of multiple degree-of-freedom input devices and virtual reality displays for interactive visual data analysis
%A Joerg Meyer
%A Hans Hagen
%A Elke Moritz
%A Thomas Wischgoll
%G eng
%0 Journal Article
%J Computer and Graphics
%D 2002
%T Topology Tracking for the Visualization of Time-Dependent Two-Dimensional Flows
%A Gerik Scheuermann
%A Xavier Tricoche
%A Hans Hagen
%A Thomas Wischgoll
%X The paper presents a topology-based visualization method for time-dependent two-dimensional vector fields. A time interpolation enables the accurate tracking of critical points and closed orbits as well as the detection and identification of structural changes. This completely characterizes the topology of the unsteady flow. Bifurcation theory provides the theoretical framework. The results are conveyed by surfaces that separate subvolumes of uniform flow behavior in a three-dimensional space-time domain.
%B Computer and Graphics
%P 249-258
%G eng
%0 Journal Article
%J IEEE Transactions on Visualization and Computer Graphics
%D 2001
%T Distributed Computation of Planar Closed Streamlines
%A Thomas Wischgoll
%A Gerik Scheuermann
%A Hans Hagen
%X The analysis and visualization of flows is a central problem in visualization. Topology based methods have gained increasing interest in recent years. This article describes a method for the detection of closed streamlines in flows. It is based on a special treatment of cases where a streamline reenters a cell to prevent infinite cycling during streamline calculation. The algorithm checks for possible exits of a loop of crossed edges and detects structurally stable closed streamlines. These global features are not detected by conventional topology and feature detection algorithms.
%B IEEE Transactions on Visualization and Computer Graphics
%P IEEE Transactions on Visualization and Computer Graphics
%G eng
%0 Journal Article
%J International Conference on Visualization, Imaging, and Image Processing
%D 2001
%T Parallel Detection of Closed Streamlines in Planar Flows
%A Gerik Scheuermann
%A Hans Hagen
%A Thomas Wischgoll
%K 2D flow
%K closed streamline
%K limit cycle
%K Linux cluster
%K parallel
%K streamline computation
%K vector field
%X Closed streamlines are an integral part of vector field topology, since they behave like sources respectively sinks but are often neither considered nor detected. If a streamline computation makes too many steps or takes too long, the computation is usually terminated without any answer on the final behavior of the streamline. We developed an algorithm that detects closed streamlines during the integration process. Since the detection of all closed streamlines in a vector field requires the computation of many streamlines we extend this algorithm to a parallel version to enhance computational speed. To test our implementation we use a numerical simulation of a swirling jet with an inflow into a steady medium. We built two different Linux clusters as parallel test systems where we check the performance increase when adding more processors to the cluster. We show that we have a very low parallel overhead due to the neglectable communication expense of our implementation.
%B International Conference on Visualization, Imaging, and Image Processing
%P 84-88
%G eng
%0 Journal Article
%J Vision, Modeling, and Visualization 2001
%D 2001
%T Tracking Closed Streamlines in Time-Dependent Planar Flows
%A Gerik Scheuermann
%A Hans Hagen
%A Thomas Wischgoll
%X Closed streamlines are a missing part in most visualizations of vector field topology. In this paper, we propose a method which detects closed streamlines in a time-dependent two-dimensional flow and investigates the behavior of these closed streamlines over time. We search in all timesteps for closed streamlines and connect them to each other in temporal order to get a tube shaped visualization. As a starting point for our investigation we look for changes of the type of critical points that lead to the creation or vanishing of closed streamlines (Hopf bifurcation). We follow the resulting limit cycle over time. In addition, changes of the topological skeleton, built by critical points and separatrices, are considered which may start or terminate the life of a closed streamline.
%B Vision, Modeling, and Visualization 2001
%P 447-454
%G eng
%0 Journal Article
%J Late Breaking Hot Topics of IEEE Symposium on Visualization 1999
%D 1999
%T Visualization of Temporal Distances
%A Gerik Scheuermann
%A Hans Hagen
%A Thomas Wischgoll
%K deformation
%K Information Visualization
%K physically based modeling
%K transport system
%X In order to visualize temporal distances, i.e. the time for traveling from one place to another, we arrange some selected cities according to these distances. In this way, the new positions reflect the connectivity of these cities with respect to time. Unlike existing approaches using tables, our method facilitates a global examination of the connectivity of a whole country. For the database, any connectivity information can be used as long as it is ensured that it is unambiguous. Therefore, any transport system can be considered and even a mixture of such systems could be visualized.
%B Late Breaking Hot Topics of IEEE Symposium on Visualization 1999
%P 43-46
%G eng