EuroVis07: Joint Eurographics - IEEE VGTC Symposium on Visualization

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https://diglib.eg.org/handle/10.2312/398

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Depth Cues and Density in Temporal Parallel Coordinates
(The Eurographics Association, 2007) Johansson, Jimmy; Ljung, Patric; Cooper, Matthew; K. Museth and T. Moeller and A. Ynnerman
This paper introduces Temporal Density Parallel Coordinates (TDPC) and Depth Cue Parallel Coordinates (DCPC) which extend the standard 2D parallel coordinates technique to capture time-varying dynamics. The proposed techniques can be used to analyse temporal positions of data items as well as temporal positions of changes occurring using 2D displays. To represent temporal changes, polygons (instead of traditional lines) are rendered in parallel coordinates. The results presented show that rendering polygons is superior at revealing large temporal changes. Both TDPC and DCPC have been efficiently implemented on the GPU allowing the visualization of thousands of data items over thousands of time steps at interactive frame rates.
Priority Streamlines: A context-based Visualization of Flow Fields
(The Eurographics Association, 2007) Schlemmer, Michael; Hotz, Ingrid; Hamann, Bernd; Morr, Florian; Hagen, Hans; K. Museth and T. Moeller and A. Ynnerman
Flow vector fields contain a wealth of information that needs to be visualized. As an extension of the well-known streamline technique, we have developed a context-based method for visualizing steady flow vector fields in two and three dimensions. We call our method "Priority Streamlines". In our approach, the density of the streamlines is controlled by a scalar function that can be user-defined, or be given by additional information (e.g., temperature, pressure, vorticity, velocity) considering the underlying flow vector field. In regions, which are interesting the streamlines are drawn with increased density, while less interesting regions are drawn sparsely. Since streamlines in the most important regions are drawn first, we can use thresholding to obtain a streamline representation highlighting essential features. Color-mapping and transparency can be used for visualizing other information hidden in the flow vector field.
TrustNeighborhoods: Visualizing Trust in Distributed File Sharing Systems
(The Eurographics Association, 2007) Elmqvist, Niklas; Tsigas, Philippas; K. Museth and T. Moeller and A. Ynnerman
We present TrustNeighborhoods, a security trust visualization for situational awareness on the Internet aimed at novice and intermediate users of a distributed file sharing system. The TrustNeighborhoods technique uses the metaphor of a multi-layered city or fortress to intuitively represent trust as a simple geographic relation. The visualization uses a radial space-filling layout; there is a 2D mode for editing and configuration, as well as a 3D mode for exploration and overview. In addition, the 3D mode supports a simple animated "fly-to" command that is intended to show the user the context and trust of a particular document by zooming in on the document and its immediate neighborhood in the 3D city. The visualization is intended for integration into an existing desktop environment, connecting to the distributed file sharing mechanisms of the environment and non-obtrusively displaying a 3D orientation animation in the background for any file being accessed over the network. A formal user study shows that the technique supports significantly higher trust assignment accuracy than manual trust assignment at the cost of only a minor time investment.
Visualization Methods for Vortex Rings and Vortex Breakdown Bubbles
(The Eurographics Association, 2007) Peikert, Ronald; Sadlo, Filip; K. Museth and T. Moeller and A. Ynnerman
Vortex breakdown bubbles are a subject which is of interest in many disciplines such as aeronautics, mixing, and combustion. Existing visualization methods are based on stream surfaces, direct volume rendering, tensor field visualization, and vector field topology. This paper presents a topological approach which is more closely oriented at the underlying theory of continuous dynamical systems. Algorithms are described for the detection of vortex rings and vortex breakdown bubbles, and for visualization of their characteristic properties such as the boundary, the chaotic dynamics, and possible islands of stability. Since some of these require very long streamlines, the effect of numerically introduced divergence has to be considered. From an existing subdivision scheme, a novel method for divergence conserving interpolation of cuboid cells is derived, and results are compared with those from standard trilinear interpolation. Also a comparison of results obtained with and without divergence cleaning is given.
Multiscale Visualization of Dynamic Software Logs
(The Eurographics Association, 2007) Moreta, Sergio; Telea, Alexandru; K. Museth and T. Moeller and A. Ynnerman
We present a set of techniques and design principles for the visualization of large dynamic software logs consisting of attributed change events, such as obtained from instrumenting programs or mining software repositories. We enhance the visualization scalability with importance-based antialiasing techniques that guarantee visibility of several types of events. We present a hierarchical clustering method that uncovers several patterns of interest in the event logs, such as same-lifetime memory allocations and software releases. We visualize the clusters using a new type of technique called interleaved cushions. We demonstrate our methods on two real-world problems: the monitoring of a dynamic memory allocator and the analysis of a software repository.
Multi-Resolution Techniques for Visual Exploration of Large Time-Series Data
(The Eurographics Association, 2007) Hao, Ming; Dayal, Umeshwar; Keim, Daniel; Schreck, Tobias; K. Museth and T. Moeller and A. Ynnerman
Time series are a data type of utmost importance in many domains such as business management and service monitoring. We address the problem of visualizing large time-related data sets which are difficult to visualize effectively with standard techniques given the limitations of current display devices. We propose a framework for intelligent time- and data-dependent visual aggregation of data along multiple resolution levels. This idea leads to effective visualization support for long time-series data providing both focus and context. The basic idea of the technique is that either data-dependent or application-dependent, display space is allocated in proportion to the degree of interest of data subintervals, thereby (a) guiding the user in perceiving important information, and (b) freeing required display space to visualize all the data. The automatic part of the framework can accommodate any time series analysis algorithm yielding a numeric degree of interest scale. We apply our techniques on real-world data sets, compare it with the standard visualization approach, and conclude the usefulness and scalability of the approach.
Relevance Driven Visualization of Financial Performance Measures
(The Eurographics Association, 2007) Ziegler, Hartmut; Nietzschmann, Tilo; Keim, Daniel A.; K. Museth and T. Moeller and A. Ynnerman
Visual data analysis has received a lot of research interest in recent years, and a wide variety of new visualization techniques and applications have been developed to improve insight into the various application domains. In financial data analysis, however, analysts still primarily rely on a set of statistical performance parameters in combination with traditional line charts in order to evaluate assets and to make decisions, and information visualization is only very slowly entering this important domain. In this paper, we analyze some of the standard statistical measures for technical financial data analysis and demonstrate cases where they produce insufficient and misleading results that do not reflect the real performance of an asset. We propose a technique for visualizing financial time series data that eliminates these inadequacies, offering a complete view on the real performance of an asset. The technique is enhanced by relevance and weighting functions according to the users' preferences in order to emphasize specific regions of interest. Based on these principles we redefine some of the standard performance measures. We apply our technique on real world financial data sets and combine it with higher-level financial analysis techniques such as performance/risk analysis, dominance evaluation, and efficiency curves in order to show how traditional techniques from economics can be improved by modern visual data analysis techniques.
Model-free Surface Visualization of Vascular Trees
(The Eurographics Association, 2007) Schumann, Christian; Oeltze, Steffen; Bade, Ragnar; Preim, Bernhard; Peitgen, H.- O.; K. Museth and T. Moeller and A. Ynnerman
Expressive and efficient visualizations of complex vascular structures are essential for medical applications, such as diagnosis and therapy planning. A variety of techniques has been developed which provide smooth high-quality visualizations of vascular structures based on rather simple model assumptions. For diagnostic applications, these model assumptions and the resulting deviations from the actual vessel surface are not acceptable. We present a model-free approach which employs the binary result of a prior vessel segmentation as input. Instead of directly converting the segmentation result into a surface, we compute a point cloud which is adaptively refined at thin structures, where aliasing effects are particularly obvious and artifacts may occur. The point cloud is transformed into a surface representation by means of MPU Implicits, which provide a smooth piecewise quadratic approximation. Our method has been applied to a variety of datasets including pathologic cases. The generated visualizations are considerably more accurate than model-based approaches. Compared to other model-free approaches, our method produces smoother results.
The CoMIRVA Toolkit for Visualizing Music-Related Data
(The Eurographics Association, 2007) Schedl, Markus; Knees, Peter; Seyerlehner, Klaus; Pohle, Tim; K. Museth and T. Moeller and A. Ynnerman
We present CoMIRVA, which is an abbreviation for Collection of Music Information Retrieval and Visualization Applications. CoMIRVA is a Java framework and toolkit for information retrieval and visualization. It is licensed under the GNU GPL and can be downloaded from http://www.cp.jku.at/comirva/. At the moment, the main functionalities include music information retrieval, web retrieval, and visualization of the extracted information. In this paper, we focus on the visualization aspects of CoMIRVA. Since many of the information retrieval functions are intended to be applied to problems of the field of music information retrieval (MIR), we demonstrate the functions using data like similarity matrices of music artists gained by analyzing artist-related web pages. CoMIRVA is continuously being extended. Currently, it supports the following visualization techniques: Self-Organizing Map, Smoothed Data Histogram, Circled Bars, Circled Fans, Probabilistic Network, Continuous Similarity Ring, Sunburst, and Music Description Map. Since space is limited, we can only present a selected number of these in this paper. As one key feature of CoMIRVA is its easy extensibility, we further elaborate on how CoMIRVA was used for creating a novel user interface to digital music repositories.
Grouse: Feature-Based, Steerable Graph Hierarchy Exploration
(The Eurographics Association, 2007) Archambault, Daniel; Munzner, Tamara; Auber, David; K. Museth and T. Moeller and A. Ynnerman
Grouse is a feature-based approach to steerable exploration of a graph and an associated hierarchy. Steerability allows exploration to begin immediately, rather than requiring a costly layout of the entire graph as an initial step. In a feature-based approach, the subgraph inside a metanode of the graph hierarchy is laid out with a well- chosen algorithm appropriate for its topological structure. Grouse preserves the input hierarchy, which provides meaningful information to the user when its metanodes correspond to features of interest. When a metanode in the hierarchy is opened, a limited number of metanodes are laid out again along the path between the opened node and the root. We demonstrate the effectiveness of Grouse on datasets from IMDB, the Internet Movie Database, where nodes are actors and cliques represent movies. The combination of feature-based layout and limited relayout computation does not fragment features in the hierarchy and improves the number of levels in the hierarchy that can be seen at once over previous approaches.
Online Dynamic Graph Drawing
(The Eurographics Association, 2007) Frishman, Yaniv; Tal, Ayellet; K. Museth and T. Moeller and A. Ynnerman
This paper presents an algorithm for drawing a sequence of graphs online. The algorithm strives to maintain the global structure of the graph and thus the user's mental map, while allowing arbitrary modifications between consecutive layouts. The algorithm works online and uses various execution culling methods in order to reduce the layout time and handle large dynamic graphs. Techniques for representing graphs on the GPU allow a speedup by a factor of up to 8 compared to the CPU implementation. An application to visualization of discussion threads in Internet sites is provided.
Sonar Explorer: A New Tool for Visualization of Fish Schools from 3D Sonar Data
(The Eurographics Association, 2007) Balabanian, Jean-Paul; Viola, Ivan; Ona, Egil; Patel, Ruben; Groeller, Eduard; K. Museth and T. Moeller and A. Ynnerman
We present a novel framework for analysis and visualization of fish schools in 3D sonar surveys. The 3D sonar technology is new and there have not been applications to visualize the data in 3D. We have created an application called Sonar Explorer that satisfies the requirements of domain scientists. Sonar Explorer provides easy and intuitive semi-automatic fish school tracking and survey map generation. The overall pipeline is described and all pipeline stages relevant for visualization are highlighted. We present techniques to deal with 3D sonar data specifics: highly anisotropic volume data aligned on a curvilinear grid. Domain scientists provide initial impressions on interaction and outlook.
Integrating Local Feature Detectors in the Interactive Visual Analysis of Flow Simulation Data
(The Eurographics Association, 2007) Buerger, Raphael; Muigg, Philipp; Ilcík, Martin; Doleisch, Helmut; Hauser, Helwig; K. Museth and T. Moeller and A. Ynnerman
We present smooth formulations of common vortex detectors that allow a seamless integration into the concept of interactive visual analysis of flow simulation data. We express the originally binary feature detectors as fuzzy-sets that can be combined using the linking and brushing concepts of interactive visual analysis. Both interaction and visualization gain from having multiple detectors concurrently available and from the ability to combine them. An application study on automotive data reveals how these vortex detectors combine and perform in praxis.
Subdivision Volume Splatting
(The Eurographics Association, 2007) McDonnell, Kevin T.; Neophytou, Neophytos; Mueller, Klaus; Qin, Hong; K. Museth and T. Moeller and A. Ynnerman
Volumetric Subdivision (VS) is a powerful paradigm that enables volumetric sculpting and realistic volume deformations that give rise to the concept of "virtual clay". In VS, volumes are commonly represented as a space-filling set of deformed polyhedra, which can be further decomposed into a mesh of tetrahedra for rendering. Images can then be generated via tetrahedral projection or raycasting. A current shortcoming in VS-based operations is the need for a very high level of subdivision to represent fine detail in the mesh and to obtain a high-fidelity visualization. However, we have discovered that the subdivision process itself can be closely simulated with radial basis functions (RBFs), making it possible to replace the finer subdivision levels by a coarser aggregation of RBF kernels. This reduction to a simplified assembly of RBFs subsequently enables interactive rendering of volumetric subdivision shapes within a GPU-based volume splatting framework.
Flexible And Topologically Localized Segmentation
(The Eurographics Association, 2007) Johansson, Gunnar; Museth, Ken; Carr, Hamish; K. Museth and T. Moeller and A. Ynnerman
One of the most common visualization tasks is the extraction of significant boundaries, often performed with isosurfaces or level set segmentation. Isosurface extraction is simple and can be guided by geometric and topological analysis, yet frequently does not extract the desired boundary. Level set segmentation is better at boundary extraction, but either leads to global segmentation without edges, [CV01], that scales unfavorably in 3D or requires an initial estimate of the boundary from which to locally solve segmentation with edges. We propose a hybrid system in which topological analysis is used for semi-automatic initialization of a level set segmentation, and geometric information bounded topologically is used to guide and accelerate an iterative segmentation algorithm that combines several state-of-the-art level set terms. We thus combine and improve both the flexible isosurface interface and level set segmentation without edges.
Animation of Orthogonal Texture-Based Vector Field Visualization
(The Eurographics Association, 2007) Bachthaler, Sven; Weiskopf, Daniel; K. Museth and T. Moeller and A. Ynnerman
This paper introduces orthogonal vector field visualization on 2D manifolds: a representation by lines that are perpendicular to the input vector field. Line patterns are generated by line integral convolution (LIC). This visualization is combined with animation based on motion along the vector field. This decoupling of the line direction from the direction of animation allows us to choose the spatial frequencies along the direction of motion independently from the length scales along the LIC line patterns. Vision research indicates that local motion detectors are tuned to certain spatial frequencies of textures, and the above decoupling enables us to generate spatial frequencies optimized for motion perception. In addition, a filtering process is described to achieve a consistent and temporally coherent animation of the orthogonal vector field visualization. We present respective visualization algorithms for 2D planar vector fields and tangential vector fields on curved surfaces, and demonstrate that those algorithms lend themselves to efficient and interactive GPU implementations.
Visualization of Uncertainty in Lattices to Support Decision-Making
(The Eurographics Association, 2007) Collins, Christopher; Carpendale, Sheelagh; Penn, Gerald; K. Museth and T. Moeller and A. Ynnerman
Lattice graphs are used as underlying data structures in many statistical processing systems, including natural language processing. Lattices compactly represent multiple possible outputs and are usually hidden from users. We present a novel visualization intended to reveal the uncertainty and variability inherent in statistically-derived lattice structures. Applications such as machine translation and automated speech recognition typically present users with a best-guess about the appropriate output, with apparent complete confidence. Through case studies we show how our visualization uses a hybrid layout along with varying transparency, colour, and size to reveal the lattice structure, expose the inherent uncertainty in statistical processing, and help users make better-informed decisions about statistically-derived outputs.
Multiresolution MIP Rendering of Large Volumetric Data Accelerated on Graphics Hardware
(The Eurographics Association, 2007) Laan, Wladimir J. van der; Jalba, Andrei C.; Roerdink, Jos B. T. M.; K. Museth and T. Moeller and A. Ynnerman
This paper is concerned with a multiresolution representation for maximum intensity projection (MIP) volume rendering based on morphological pyramids which allows progressive refinement. We consider two algorithms for progressive rendering from the morphological pyramid: one which projects detail coefficients level by level, and a second one, called streaming MIP, which resorts the detail coefficients of all levels simultaneously with respect to decreasing magnitude of a suitable error measure. The latter method outperforms the level-by-level method, both with respect to image quality with a fixed amount of detail data, and in terms of flexibility of controlling approximation error or computation time. We improve the streaming MIP algorithm, present a GPU implementation for both methods, and perform a comparison with existing CPU and GPU implementations.
Interactive Visualization of Multi-Field Medical Data Using Linked Physical and Feature-Space Views
(The Eurographics Association, 2007) Blaas, Jorik; Botha, Charl P.; Post, Frits H.; K. Museth and T. Moeller and A. Ynnerman
Multi-field datasets contain multiple parameters defined over the same spatio-temporal domain. In medicine, such multi-field data is being used more often every day, and there is an urgent need for exploratory visualization approaches that are able to deal effectively with the data-analysis. In this paper, we present a highly interactive, coordinated view-based visualization approach that has been developed especially for dealing with multi-field medical data. It can show any number of views of the physical domain and also of the abstract high-dimensional feature space. The approach has been optimized for interactive use with very large datasets. It is based on intuitive interaction techniques, and integrates analysis techniques from pattern classification to guide the exploration process. We will give some details about the implementation, and we demonstrate the utility of our approach with two real medical use cases.
Path Visualization for Adjacency Matrices
(The Eurographics Association, 2007) Shen, Zeqian; Ma, Kwan-Liu; K. Museth and T. Moeller and A. Ynnerman
For displaying a dense graph, an adjacency matrix is superior than a node-link diagram because it is more compact and free of visual clutter. A node-link diagram, however, is far better for the task of path finding because a path can be easily traced by following the corresponding links, provided that the links are not heavily crossed or tangled.We augment adjacency matrices with path visualization and associated interaction techniques to facilitate path finding. Our design is visually pleasing, and also effectively displays multiple paths based on the design commonly found in metro maps. We illustrate and assess the key aspects of our design with the results obtained from two case studies and an informal user study.

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