VisSym04: Joint Eurographics - IEEE TCVG Symposium on Visualization

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Illustrating Surfaces in Volume

Yuan, Xiaoru
Chen, Baoquan

A Cluster-Space Visual Interface for Arbitrary Dimensional Classification of Volume Data

Tzeng, Fan-Yin
Ma, Kwan-Liu

Interactively Visualizing Procedurally Encoded Scalar Fields

Jang, Yun
Weiler, Manfred
Hopf, Matthias
Huang, Jingshu
Ebert, David S.
Gaither, Kelly P.
Ertl, Thomas

High-Quality Lighting and Efficient Pre-Integration for Volume Rendering

Lum, Eric B.
Wilson, Brett
Ma, Kwan-Liu

Shape-Embedded-Histograms for Visual Data Mining

Amir, Amihood
Kashi, Reuven
Keim, Daniel A.
Netanyahu, Nathan S.
Wawryniuk, Markus

Graph Drawing by Subspace Optimization

Koren, Yehuda

TimeHistograms for Large, Time-Dependent Data

Kosara, Robert
Bendix, Fabian
Hauser, Helwig

Visual Triangulation of Network-Based Phylogenetic Trees

Brandes, U.
Dwyer, T.
Schreiber, F.

Case Study: Visual Analysis of Complex, Time-Dependent Simulation Results of a Diesel Exhaust System

Doleisch, Helmut
Mayer, Michael
Gasser, Martin
Wanker, Roland
Hauser, Helwig

Texture-Based Flow Visualization on Isosurfaces from Computational Fluid Dynamics

Laramee, Robert S.
Schneider, Jürgen
Hauser, Helwig

Accuracy Evaluation of Different Centerline Approximations of Blood Vessels

Cruz, A. La

Visualising Organisms with Hydraulic Body Parts: A Case Study in Integrating Simulation and Visualisation Models

Breiner, T.
Dörner, R.
Seiler, C.
Gudo, M.

Case Study: Visualization of annotated DNA sequences

Peeters, Tim
Fiers, Mark
Wetering, Huub van de
Nap, Jan-Peter
Wijk, Jarke J. van

Visualization For Public-Resource Climate Modeling

Stainforth, D.A.
Frame, D.
Walton, J.P.R.B.

Visual Component Analysis

Müller, Wolfgang
Alexa, Marc

Interactive TreemapsWith Detail on Demand to Support Information Search in Documents

Schlechtweg, Stefan
Schulze-Wollgast, Petra
Schumann, Heidrun

Superquadric Tensor Glyphs

Kindlmann, Gordon

Interaction Spaces in Data and Information Visualization

Ward, M.
Yang, J.

Techniques for Visualizing Multi-Valued Flow Data

Urnessy, Timothy
Interrante, Victoria
Longmire, Ellen
Marusic, Ivan
Ganapathisubramani, Bharathram

Surface Techniques for Vortex Visualization

Garth, Christoph
Tricoche, Xavier
Salzbrunn, Tobias
Bobach, Tom
Scheuermann, Gerik

Boundary Switch Connectors for Topological Visualization of Complex 3D Vector Fields

Weinkauf, T.
Theisel, H.
Hege, H.-C.
Seidel, H.-P.

Ray Casting Curved-Quadratic Elements

Wiley, D. F.
Childs, H. R.
Hamann, B.
Joy, K. I.

Auralization I: Vortex Sound Synthesis

Shin, Youngin
Bajaj, Chandrajit

DTI Visualization with Streamsurfaces and Evenly-Spaced Volume Seeding

Vilanova, A.
Berenschot, G.
Pul, C. van

Generalized Distance Transforms and Skeletons in Graphics Hardware

Strzodka, R.
Telea, A.

A Botanically Inspired High-Dimensional Visualization with Multivariate Glyphs

Chlan, E. B.
Rheingans, Penny

Interactive High Quality Trimmed NURBS Visualization Using Appearance Preserving Tessellation

Guthe, M.
Balázs, Á.
Klein, R.

Browsing and Visualizing Digital Bibliographic Data

Klink, Stefan
Ley, Michael
Rabbidge, Emma
Reuther, Patrick
Walter, Bernd
Weber, Alexander

Visualization of Cardio-CT Data on Standard PC Hardware

Bauer, Michael

Volume Visualization and Visual Queries for Large High-Dimensional Datasets

Reina, G.
Ertl, T.

Medical Applications of Multi-Field Volume Rendering and VR Techniques

Kniss, Joe
Schulze, Jürgen P.
Wössner, Uwe
Winkler, Peter
Lang, Ulrich
Hansen, Charles

Software Landscapes: Visualizing the Structure of Large Software Systems

Balzer, Michael
Noack, Andreas
Deussen, Oliver
Lewerentz, Claus

Efficient Isosurface Tracking Using Precomputed Correspondence Table

Ji, Guangfeng
Shen, Han-Wei

Meshless Isosurface Generation from Multiblock Data

Co, Christopher S.
Porumbescu, Serban D.
Joy, Kenneth I.

Occlusion Culling for Sub-Surface Models in Geo-Scientific Applications

Plate, John
Grundhoefer, Anselm
Schmidt, Benjamin
Froehlich, und Bernd

Visualization of Anatomic Tree Structures with Convolution Surfaces

Oeltze, S.
Preim, B.

Adaptive Volume Construction from Ultrasound Images of a Human Heart

Reis, Gerd
Bertram, Martin
Lengen, Rolf H. van
Hagen, Hans

Efficient Display of Background Objects for Virtual Endoscopy using Flexible First-Hit Ray Casting

Neubauer, A.
Forster, M.
Wegenkittl, R.
Mroz, L.
Bühler, K.

Efficient Isosurface Tracking Using Precomputed Correspondence Table

Ji, Guangfeng
Shen, Han-Wei


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Now showing 1 - 39 of 39
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    Illustrating Surfaces in Volume
    (The Eurographics Association, 2004) Yuan, Xiaoru; Chen, Baoquan; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    This paper presents a novel framework for illustrating surfaces in a volume. Surfaces are illustrated by drawing only feature lines, such as silhouettes, valleys, ridges, and surface hatching strokes, and are embedded in volume renderings. This framework promises effective illustration of both surfaces and volumes without occluding or cluttering each other. A two-step approach has been taken: the first step depicts surfaces; the second step performs volume rendering, at the same time embedding surfaces from the first step. We introduce Procedurally Perturbed Image Processing (PIP), a new method for enhancing both feature detection and depiction of surfaces. We also present implementation strategies, especially those leveraging modern graphics hardware, for delivering an interactive rendering system. Our implementation results have shown that this mixed form of rendering improves volume visualization and is efficient.
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    A Cluster-Space Visual Interface for Arbitrary Dimensional Classification of Volume Data
    (The Eurographics Association, 2004) Tzeng, Fan-Yin; Ma, Kwan-Liu; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    In volume visualization, users typically specify transfer functions to classify the data and assign visual attributes to each material class. Higher-dimensional classification makes it easier to differentiate material classes since more data properties are considered. One of the difficulties in using higher-dimensional classification is the absence of appropriate user interfaces. We introduce an intuitive user interface that allows the user to work in the cluster space, which shows the material classes with a set of material widgets, rather than work in the transfer function space. This interface not only provides the user the capability to specify arbitrary-dimensional transfer functions, but also allows the user to operate directly on the classification and visualization results.
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    Interactively Visualizing Procedurally Encoded Scalar Fields
    (The Eurographics Association, 2004) Jang, Yun; Weiler, Manfred; Hopf, Matthias; Huang, Jingshu; Ebert, David S.; Gaither, Kelly P.; Ertl, Thomas; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    While interactive visualization of rectilinear gridded volume data sets can now be accomplished using texture mapping hardware on commodity PCs, interactive rendering and exploration of large scattered or unstructured data sets is still a challenging problem. We have developed a new approach that allows the interactive rendering and navigation of procedurally-encoded 3D scalar fields by reconstructing these fields on PC class graphics processing units. Since the radial basis functions (RBFs) we use for encoding can provide a compact representation of volumetric scalar fields, the large grid/mesh traditionally needed for rendering is no longer required and ceases to be a data transfer and computational bottleneck during rendering. Our new approach will interactively render RBF encoded data obtained from arbitrary volume data sets, including both structured volume models and unstructured scattered volume models. This procedural reconstruction of large data sets is flexible, extensible, and can take advantage of the Moore's Law cubed increase in performance of graphics hardware.
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    High-Quality Lighting and Efficient Pre-Integration for Volume Rendering
    (The Eurographics Association, 2004) Lum, Eric B.; Wilson, Brett; Ma, Kwan-Liu; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Pre-integrated volume rendering is an effective technique for generating high-quality visualizations. The precomputed lookup tables used by this method are slow to compute and can not include truly pre-integrated lighting due to space constraints. The lighting for pre-integrated rendering is therefore subject to the same sampling artifacts as in standard volume rendering. We propose methods to speed up lookup table generation and minimize lighting artifacts. The incremental subrange integration method we describe allows interactive lookup table generation in O(n<sup>2</sup>) time without the need for approximation or hardware assistance. The interpolated preintegrated lighting algorithm eliminates discontinuities by linearly interpolating illumination along the view direction. Both methods are applicable to any pre-integrated rendering method, including cell projection, ray casting, and hardware-accelerated algorithms.
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    Shape-Embedded-Histograms for Visual Data Mining
    (The Eurographics Association, 2004) Amir, Amihood; Kashi, Reuven; Keim, Daniel A.; Netanyahu, Nathan S.; Wawryniuk, Markus; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Scatterplots are widely used in exploratory data analysis and class visualization. The advantages of scatterplots are that they are easy to understand and allow the user to draw conclusions about the attributes which span the projection screen. Unfortunately, scatterplots have the overplotting problem which is especially critical when high-dimensional data are mapped to low-dimensional visualizations. Overplotting makes it hard to detect the structure in the data, such as dependencies or areas of high density. In this paper we show that by extending the concept of Pixel Validity (1) the problem of overplotting or occlusion can be avoided and (2) the user has the possibility to see information about an additional third variable. In our extension of the Pixel Validity concept, we summarize the data which are projected onto a given region by generating a histogram over the required attribute. This is then embedded in the visualization by a pixel-based technique.
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    Graph Drawing by Subspace Optimization
    (The Eurographics Association, 2004) Koren, Yehuda; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    We show a novel approach for accelerating the computation of graph drawing algorithms. The method is based on the notion that we can find a subspace with a relatively low dimensionality that captures the "nice" layouts of the graph. This way each axis of the drawing is a linear combination of a few basis vectors, instead of being an arbitrary vector in Rn (n is the number of nodes). We describe ways of constructing these basis vectors and also algorithms for optimizing the graph drawing in the resulting subspace.
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    TimeHistograms for Large, Time-Dependent Data
    (The Eurographics Association, 2004) Kosara, Robert; Bendix, Fabian; Hauser, Helwig; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Histograms are a very useful tool for data analysis, because they show the distribution of values over a data dimension. Many data sets in engineering (like computational fluid dynamics, CFD), however, are time-dependent. While standard histograms can certainly show such data sets, they do not account for the special role time plays in physical processes and our perception of the world. We present TimeHistograms, which are an extension to standard histograms that take time into account. In several 2D and 3D views, the data is presented in different ways that allow the user to understand different aspects of the temporal development of a dimension. A number of interaction techniques are also provided to make best use of the display, and to allow the user to brush in the histograms.
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    Visual Triangulation of Network-Based Phylogenetic Trees
    (The Eurographics Association, 2004) Brandes, U.; Dwyer, T.; Schreiber, F.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Phylogenetic trees are built by examining differences in the biological traits of a set of species. An example of such a trait is a biological network such as a metabolic pathway, common to all species but with subtle differences in each. Phylogenetic trees of metabolic pathways represent multiple aspects of similarity and hypothetical evolution in a single, yet complex structure that is difficult to understand and interpret. We present a visualization method that facilitates analysis of such structures by presenting multiple coordinated perspectives simultaneously. Each of these perspectives constitutes a useful visualization in its own right, but it is only together that they unfold their full explorative power.
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    Case Study: Visual Analysis of Complex, Time-Dependent Simulation Results of a Diesel Exhaust System
    (The Eurographics Association, 2004) Doleisch, Helmut; Mayer, Michael; Gasser, Martin; Wanker, Roland; Hauser, Helwig; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    In previous work we have presented visualization techniques that provide engineers with a high degree of interactivity and flexibility for analyzing large, time-dependent, and high-dimensional data sets resulting from CFD (computational fluid dynamics) simulations. In this case study we apply our techniques in the fields of the automotive engineering industry and demonstrate how users benefit from using them during their routine analysis, as well as for exploring new phenomena. For coping with some of the special requirements in this application, we adapted and extended parts of the system. A comparison of two related cases of a diesel exhaust system is presented, and some important questions about these cases are addressed.
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    Texture-Based Flow Visualization on Isosurfaces from Computational Fluid Dynamics
    (The Eurographics Association, 2004) Laramee, Robert S.; Schneider, Jürgen; Hauser, Helwig; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Isosurfacing, by itself, is a common visualization technique for investigating 3D vector fields. Applying texturebased flow visualization techniques to isosurfaces provides engineers with even more insight into the characteristics of 3D vector fields. We apply a method for producing dense, texture-based representations of flow on isosurfaces. It combines two well know scientific visualization techniques, namely iso-surfacing and texture-based flow visualization, into a useful hybrid approach. The method is fast and can generate dense representations of flow on isosurfaces with high spatio-temporal correlation at 60 frames per second. The method is applied in the context of CFD simulation data, namely, the investigation of a common swirl flow pattern and the visualization of blood flow.
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    Accuracy Evaluation of Different Centerline Approximations of Blood Vessels
    (The Eurographics Association, 2004) Cruz, A. La; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Accurate determination of the vessel axis is a prerequisite for automated visualization and quantification of artery diseases. This paper presents an evaluation of different methods for approximating the centerline of the vessel in a phantom simulating the peripheral arteries. Six algorithms were used to determine the centerline of a synthetic peripheral arterial vessel. They are based on: ray casting using thresholds and maximum gradient-like stop criterion, pixel motion estimation between successive images called block matching, center of gravity and shape based segmentation. The Randomized Hough Transform and ellipse fitting have been used as shape based segmentation techniques. Since in the synthetic data set the centerline is known, an estimation of the error can be calculated in order to determine the accuracy achieved by a given method.
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    Visualising Organisms with Hydraulic Body Parts: A Case Study in Integrating Simulation and Visualisation Models
    (The Eurographics Association, 2004) Breiner, T.; Dörner, R.; Seiler, C.; Gudo, M.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    The physical structure of organisms can be modelled as a set of coupled hydraulic entities. The hydropneumatic biosimulation is a methodology that is able to simulate the behavior (like movements) of such organisms on the physical level in a biological correct way. Hydropneumatic simulation heavily relies on visualisation: the simulation model is visually constructed and the simulation results are presented visually to the user. This case study presents an approach, how a visualisation of the results of a hydropneumatic biosimulation can be obtained by integrating the biological simulation model with a Computer Graphics geometry model.
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    Case Study: Visualization of annotated DNA sequences
    (The Eurographics Association, 2004) Peeters, Tim; Fiers, Mark; Wetering, Huub van de; Nap, Jan-Peter; Wijk, Jarke J. van; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    DNA sequences and their annotations form ever expanding data sets. Proper explorations of such data sets require new tools for visualization and analysis. In this case study, we have defined the requirements for a visualization tool for annotated DNA sequences.We have implemented these requirements in a new and flexible tool for browsing and comparing annotated DNA sequences interactively and in real-time. The use of standard information visualization techniques, such as linked windows, perspective walls, and smooth interaction, enables genome researchers to obtain better insight in large DNA data sets in an effective, efficient, and attractive way.
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    Visualization For Public-Resource Climate Modeling
    (The Eurographics Association, 2004) Stainforth, D.A.; Frame, D.; Walton, J.P.R.B.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Climateprediction.net aims to harness the spare CPU cycles of a million individual users PCs to run a massive ensemble of climate simulations using an up-to-date, full-scale 3D atmosphere-ocean climate model. Although it has many similarities with other public-resource computing projects, it is distinguished by the complexity of its computational task, its system demands and the level of participant interaction, data volume and analysis procedures. For simulations running on individual PCs, there is a requirement for visualizations that are compelling and readily grasped, since most users will be interested in the output from the model, but will have a limited level of scientific experience. This paper describes the design and implementation of these visualizations.
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    Visual Component Analysis
    (The Eurographics Association, 2004) Müller, Wolfgang; Alexa, Marc; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    We propose to integrate information visualization techniques with factor analysis. Specifically, a principal direction derived from a principal component analysis (PCA) of the data is displayed together with the data in a scatterplot matrix. The direction can be adjusted to coincide with visual trends in the data. Projecting the data onto the orthogonal subspace allows determining the next direction. The set of directions identified in this way forms an orthogonal space, which represents most of the variation in the data. We call this process visual component analysis (VCA). Furthermore, it is quite simple to integrate VCA with clustering. The user fits poly-lines to the displayed data, and the poly-lines implicitly define clusters. Per-cluster projection leads to the definition of per-cluster components.
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    Interactive TreemapsWith Detail on Demand to Support Information Search in Documents
    (The Eurographics Association, 2004) Schlechtweg, Stefan; Schulze-Wollgast, Petra; Schumann, Heidrun; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    This paper addresses the issue of how information visualization techniques can be used to assist full-text search in electronic documents. Our approach supports multiple term queries with interactive treemaps. We use a treemap to visualize the basic structure of the document and exploit color coding to show the distribution of query terms on various levels of the hierarchy. Furthermore, we include filtering techniques to concentrate on those parts of the structure that actually contain the requested information, and, finally provide interactive tools to give access to detailed information whenever the user wishes.
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    Superquadric Tensor Glyphs
    (The Eurographics Association, 2004) Kindlmann, Gordon; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Tensor field visualization is a challenging task due in part to the multi-variate nature of individual tensor samples. Glyphs convey tensor variables by mapping the tensor eigenvectors and eigenvalues to the orientation and shape of a geometric primitive, such as a cuboid or ellipsoid. Though widespread, cuboids and ellipsoids have problems of asymmetry and visual ambiguity. Cuboids can display misleading orientation for tensors with underlying rotational symmetry. Ellipsoids differing in shape can be confused, from certain viewpoints, because of similarities in profile and shading. This paper addresses the problems of asymmetry and ambiguity with a new tunable continuum of glyphs based on superquadric surfaces. Superquadric tensor glyphs enjoy the necessary symmetry properties of ellipsoids, while also imitating cuboids and cylinders to better convey shape and orientation, where appropriate. The new glyphs are demonstrated on fields of diffusion tensors from the human brain.
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    Interaction Spaces in Data and Information Visualization
    (The Eurographics Association, 2004) Ward, M.; Yang, J.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    User interaction plays an integral part in the effective visualization of data and information. Typical interaction operations include navigation, selection, and distortion. A problem that can occur when these operations are speci£ed using direct manipulation is determining which object or space is the focus of the interaction. In some operations the user wants to indicate a region of an image, while in others the focus might be the data being projected or the surface upon which the projection is occurring. In this paper we attempt to identify a complete list of spaces within which interactive operations can occur in data and information visualization. These interaction spaces help disambiguate the focus of interactive operations, and their study can potentially reveal new and powerful methods for supporting the visual exploration process. We de£ne the distinctions between the spaces and provide examples of interactions within each space.
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    Techniques for Visualizing Multi-Valued Flow Data
    (The Eurographics Association, 2004) Urnessy, Timothy; Interrante, Victoria; Longmire, Ellen; Marusic, Ivan; Ganapathisubramani, Bharathram; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    In this paper we discuss several techniques to display multiple scalar distributions within an image depicting a 2D flow field. We first address how internal contrast and mean luminance can effectively be used to represent a scalar distribution in addition to an underlying flow field. Secondly, we expand upon a current technique to more effectively use luminance ramps over dense streamlines to represent direction of flow. Lastly, we present a new method, based on embossing, to encode the out-of-plane component of a 3D vector field defined over a 2D domain. Throughout this paper, we limit our focus to the visualization of steady flows.
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    Surface Techniques for Vortex Visualization
    (The Eurographics Association, 2004) Garth, Christoph; Tricoche, Xavier; Salzbrunn, Tobias; Bobach, Tom; Scheuermann, Gerik; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    This paper presents powerful surface based techniques for the analysis of complex flow fields resulting from CFD simulations. Emphasis is put on the examination of vortical structures. An improved method for stream surface computation that delivers accurate results in regions of intricate flow is presented, along with a novel method to determine boundary surfaces of vortex cores. A number of surface techniques are presented that aid in understanding the flow behavior displayed by these surfaces. Furthermore, a scheme for phenomenological extraction of vortex core lines using stream surfaces is discussed and its accuracy is compared to one of the most established standard techniques.
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    Boundary Switch Connectors for Topological Visualization of Complex 3D Vector Fields
    (The Eurographics Association, 2004) Weinkauf, T.; Theisel, H.; Hege, H.-C.; Seidel, H.-P.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    One of the reasons that topological methods have a limited popularity for the visualization of complex 3D flow fields is the fact that their topological structures contain a number of separating stream surfaces. Since these stream surfaces tend to hide each other as well as other topological features, for complex 3D topologies the visualizations become cluttered and hardly interpretable. One solution of this problem is the recently introduced concept of saddle connectors which treats separation surfaces emanating from critical points. In this paper we extend this concept to separation surfaces starting from boundary switch curves. This way we obtain a number of particular stream lines called boundary switch connectors. They connect either two boundary switch curves or a boundary switch curve with a saddle. We discuss properties and computational issues of boundary switch connectors and apply them to topologically complex flow data.
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    Ray Casting Curved-Quadratic Elements
    (The Eurographics Association, 2004) Wiley, D. F.; Childs, H. R.; Hamann, B.; Joy, K. I.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    We present a method for ray casting curved-quadratic elements in 3D. The advantages of this approach is that a curved element can be directly visualized. Conventionally, higher-order elements are tessellated with several linear elements so that standard visualization techniques can be applied to the linear elements. Our method primarily focuses on how to find an approximation to the intersection between a ray and a curved-quadratic element. Once this approximation is found, conventional accumulation and color mapping techniques can be applied to the approximation to produce a volumetric visualization of the element. A cutting plane implementation is also shown that leverages the ray casting technique.
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    Auralization I: Vortex Sound Synthesis
    (The Eurographics Association, 2004) Shin, Youngin; Bajaj, Chandrajit; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Auralization is the process of extracting and displaying meaningful information in the form of sound from data. Through not only visualization but also auralization, users may have better understandings of the data, especially when it is visually complicated. In this work, a field auralization technique is introduced, which objective is at the sound synthesis from field information represented as 3D time-varying volume data. Our technique takes a hybrid approach between parameter mapping and direct simulation. During preprocessing, acoustic strengths are computed at each vertex at each time step of volume data. During interaction, users navigate within the volume space and audio frames are computed by integrating the radiations from the sources. A number of problems inherent in this problem and our solutions are discussed.
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    DTI Visualization with Streamsurfaces and Evenly-Spaced Volume Seeding
    (The Eurographics Association, 2004) Vilanova, A.; Berenschot, G.; Pul, C. van; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Experimental evidence has shown that water diffusion is anisotropic in organized tissues such as white matter or muscles. Diffusion Tensor Imaging is a non-invasive MR technique that measures water diffusion. DTI is used to visualize linear structures such as fibers. In this paper, we present a visualization tool for DTI data. A new algorithm to visualize linear structures in areas of crossing or converging fibers is presented. Usually the user defines an area from where the fibers are generated. In this way, the user can miss part of the information, if the area is not correctly defined. We present a method to visualize the structures in the whole volume with an evenly-spaced distance between them. Some results obtained by our partners using the DTI tool will be presented.
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    Generalized Distance Transforms and Skeletons in Graphics Hardware
    (The Eurographics Association, 2004) Strzodka, R.; Telea, A.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    We present a framework for computing generalized distance transforms and skeletons of two-dimensional objects using graphics hardware. Our method is based on the concept of footprint splatting. Combining different splats produces weighted distance transforms for different metrics, as well as the corresponding skeletons and Voronoi diagrams. We present a hierarchical acceleration scheme and a subdivision scheme that allows visualizing the computed skeletons with subpixel accuracy in real time. Our splatting approach allows one to easily change all the metric parameters, treat any 2D boundaries, and easily produce both DTs and skeletons. We illustrate the method by several examples.
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    A Botanically Inspired High-Dimensional Visualization with Multivariate Glyphs
    (The Eurographics Association, 2004) Chlan, E. B.; Rheingans, Penny; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    It is difficult for the average viewer to assimilate and comprehend huge amounts of high-dimensional data. It is important to present data in a way that allows the user a high level understanding of the overall organization and structure without losing the ability to study low level detail as needed. Although hierarchically clustered data is already organized, many current means of presenting such data give the user little more than an overview of the organization. It would be useful to see more information about the data even at a high level and to examine specific clusters as needed. We want to understand the relationships of the clusters in terms of the underlying data, and to understand the extent and variability of the data without requiring examination of each data item. To meet these goals, we present an aesthetically appealing visualization based on botanical trees which preserves the natural order of hierarchically organized data. Hierarchical data is rendered as a simple branched tree. The tree gives an overview of the relationships among various clusters and is supplemented with two glyphs which allow the user to focus in on specific clusters of the data at different levels of detail. At a medium level of focus, a cluster glyph based on a radial, space filling approach shows the subtree rooted at a specified cluster. At a low level of detail, the branch glyph allows the viewer to see not only aggregate information about the cluster but the extent and variability of the component clusters.
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    Interactive High Quality Trimmed NURBS Visualization Using Appearance Preserving Tessellation
    (The Eurographics Association, 2004) Guthe, M.; Balázs, Á.; Klein, R.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Trimmed NURBS models are the standard representation used in CAD/CAM systems and accurate visualization of large trimmed NURBS models at interactive frame rates is of great interest for industry. To visualize the quality of a surface several techniques like isophotes, reflection lines, etc. are used. Most existing approaches transform the NURBS surfaces into a fine polygonal representation and build static levels of detail from this representation. This polygonal approximation together with its normals are adjusted in a semi-automatic procedure to achieve the desired visual fidelity during visualization. Since this approach allows only for a fixed maximum accuracy and does not support deformable models, another more recent approach is to keep the NURBS representation and generate view-dependent LODs on the fly up to the currently required preciseness. However, so far this approach took only into account the geometric error of an approximation and thus neglected the various illumination artifacts introduced by the chosen (possibly view-dependent) triangulation. Although this problem can be solved by using normal maps, the resolution of the normal maps again limits the accuracy. Furthermore, the normal map generation requires a preprocessing step which prevents the support of deformable NURBS models. In this paper we present a novel automatic tessellation algorithm that considers the illumination artifacts and is well suited both for the generation of static and dynamic LOD schemes with guaranteed visual fidelity. Our new method is also capable of high quality visualization of further attributes like curvature, temperature, etc. on surfaces with little or no modification.
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    Browsing and Visualizing Digital Bibliographic Data
    (The Eurographics Association, 2004) Klink, Stefan; Ley, Michael; Rabbidge, Emma; Reuther, Patrick; Walter, Bernd; Weber, Alexander; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Access to publications is provided by conventional libraries, digital libraries operated by learned societies or commercial publishers, and a huge number of web sites maintained by the scientists themselves or their institutions. But comprehensive meta-indices in combination with a helpful graphical user interface for this increasing number of information sources are missing for most areas of science. Our DBLP (Digital Bibliography & Library Project) Computer Science Bibliography is a major service used by thousands of computer scientists. It provides fundamental support for scientists searching for publications or other scientists in similar communities. For better assistance we developed a new browser prototype which has a user-friendly interface and plays a central role in the search and browsing of the data. The DBL-Browser provides smart search functions and several textual and graphical visualization models. This paper gives an overview of some important research issues within the field of bibliographical information retrieval and visualization. After introducing the whole framework, the DBL-Browser itself and various visualization models are described.
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    Visualization of Cardio-CT Data on Standard PC Hardware
    (The Eurographics Association, 2004) Bauer, Michael; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    In the last years, texture based volume rendering on the PC platform has proven very successful. Many methods that could formerly only be done with software renderers can now be done completely by the graphics hardware. In this paper we present first results of our ongoing work that deals with the visualization of time dependent CT data of the human heart. We compare the drawbacks and benefits of 3D and 2D texture based methods. We also show that a high quality shaded rendering can considerably improve the visual quality. Then we present our results in the area of classification methods, especially using two-dimensional classification. Finally we demonstrate that it is possible to visualize a beating heart using moderately sized time dependent Cardio-CT data.
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    Volume Visualization and Visual Queries for Large High-Dimensional Datasets
    (The Eurographics Association, 2004) Reina, G.; Ertl, T.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    We propose a flexible approach for the visualization of large, high-dimensional datasets. The raw, highdimensional data is mapped into an abstract 3D distance space using the FastMap algorithm, which helps, together with other linear preprocessing steps, to make changes to the resulting 3D representation within a few seconds. Thus exploration of such datasets is a less tedious task compared to other techniques. We use volumes with four components to enable the user to brush an attribute selection onto the volume for inspection. We exploit multiple transfer functions for displaying these attributes and also to filter one attribute with values of another. An advantage of this volume sampling approach is that the rendering performance is independent of the dataset size. The drawback of limited resolution can be overcome by providing a linked detail view for a freely selectable portion of space. Examples of the inspection and filtering possibilities using a silvicultural dataset illustrate the strengths of our approach.
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    Medical Applications of Multi-Field Volume Rendering and VR Techniques
    (The Eurographics Association, 2004) Kniss, Joe; Schulze, Jürgen P.; Wössner, Uwe; Winkler, Peter; Lang, Ulrich; Hansen, Charles; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    This paper reports on a new approach for visualizing multi-field MRI or CT datasets in an immersive environment with medical applications. Multi-field datasets combine multiple scanning modalities into a single 3D, multivalued, dataset. In our approach, they are classified and rendered using real-time hardware accelerated volume rendering, and displayed in a hybrid work environment, consisting of a dual power wall and a desktop PC. For practical reasons in this environment, the design and use of the transfer functions is subdivided into two steps, classification and exploration. The classification step is done at the desktop, taking advantage of the 2D mouse as a high accuracy input device. The exploration process takes place on the powerwall.We present our new approach, describe the underlying implementation issues, report on our experiences with different immersive environments, and suggest ways it can be used for collaborative medical diagnosis and treatment planning.
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    Software Landscapes: Visualizing the Structure of Large Software Systems
    (The Eurographics Association, 2004) Balzer, Michael; Noack, Andreas; Deussen, Oliver; Lewerentz, Claus; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Modern object-oriented programs are hierarchical systems with many thousands of interrelated subsystems. Visualization helps developers to better comprehend these large and complex systems. This paper presents a three-dimensional visualization technique that represents the static structure of object-oriented programs using landscape-like distributions of three-dimensional objects on a two-dimensional plane. The familiar landscape methaphor facilitates intuitive navigation and comprehension. The visual complexity is reduced by adjusting the transparency of object surfaces to the distance of the viewpoint. An approach called Hierarchical Net is proposed for a clear representation of the relationsships between the subsystems.
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    Efficient Isosurface Tracking Using Precomputed Correspondence Table
    (The Eurographics Association, 2004) Ji, Guangfeng; Shen, Han-Wei; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Feature tracking is a useful method for visualizing and analyzing time-varying scalar fields. It allows scientists to focus on regions of interest and track their evolution and interaction over time. To allow the user to freely explore the data set, features must be tracked in an efficient manner. In this paper, we present an efficient time-varying isosurface tracking algorithm. Unlike the previous algorithms which compute the corresponding isosurface components in the adjacent time steps by performing expensive computation at run time, our algorithm can rapidly identify corresponding isosurfaces by performing simple table lookup operations. This table, called the correspondence lookup table, can be computed at a preprocessing stage. The idea behind our approach is that the correspondence relationship can only change at critical isovalues in R3 or R4 and remains unchanged between adjacent pairs of critical isovalues. With our algorithm, isosurfaces can be tracked in an efficient manner with minimal overhead.
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    Meshless Isosurface Generation from Multiblock Data
    (The Eurographics Association, 2004) Co, Christopher S.; Porumbescu, Serban D.; Joy, Kenneth I.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    We propose a meshless method for the extraction of high-quality continuous isosurfaces from volumetric data represented by multiple grids, also called "multiblock" data sets. Multiblock data sets are commonplace in computational mechanics applications. Relatively little research has been performed on contouring multiblock data sets, particularly when the grids overlap one another. Our algorithm proceeds in two steps. In the first step, we determine a continuous interpolant using a set of locally defined radial basis functions (RBFs) in conjunction with a partition of unity method to blend smoothly between these functions. In the second step, we extract isosurface geometry by sampling points on Marching Cubes triangles and projecting these point samples onto the isosurface defined by our interpolant. A surface splatting algorithm is employed for visualizing the resulting point set representing the isosurface. Because of our method s generality, it inherently solves the "crack problem" in isosurface generation. Results using a set of synthetic data sets and a discussion of practical considerations are presented. The importance of our method is that it can be applied to arbitrary grid data regardless of mesh layout or orientation.
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    Occlusion Culling for Sub-Surface Models in Geo-Scientific Applications
    (The Eurographics Association, 2004) Plate, John; Grundhoefer, Anselm; Schmidt, Benjamin; Froehlich, und Bernd; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Modern graphics cards support occlusion culling in hardware. We present a three pass algorithm, which makes efficient use of this feature. Our geo-scientific sub-surface data sets consist typically of a set of high resolution height fields, polygonal objects, and volume slices and lenses. For each height field, we compute a low and high resolution version in a pre-process and divide both into sets of corresponding tiles. For each tile and for the polygonal objects, the first rendering pass computes a z-buffer image using the low resolution tiles, the polygonal objects and the non-transparent volume objects. During the second pass, we render the same objects against the z-buffer of the first pass while submitting an occlusion query with each object. The third pass reads this occlusion information back from the graphics hardware and renders only those high resolution objects, for which the corresponding low resolution objects were not completely occluded. To avoid fill rate bottle necks, the first two passes may be rendered to a low resolution window. Our implementation shows frame rate improvements for all test cases while introducing only a small overhead and no or hardly noticeable errors. Our non-conservative approach does not require front to back sorting and it works for dynamic scenes.
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    Visualization of Anatomic Tree Structures with Convolution Surfaces
    (The Eurographics Association, 2004) Oeltze, S.; Preim, B.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    We present a method for visualizing anatomic tree structures, such as vasculature and bronchial trees based on clinical CT- or MR data. The vessel skeleton as well as the diameter information per voxel serve as input. Our method adheres to these data, while producing smooth transitions at branchings and closed, rounded ends by means of convolution surfaces. We discuss the filter design with respect to irritating bulges, unwanted blending and the correct visualization of the vessel diameter. Similar to related work our method is based on the assumption of a circular cross-section of vasculature. In contrast to other authors we employ implicit surfaces to achieve high quality visualization. The method has been applied to a large variety of anatomic trees and produces good results. The time to construct a geometric model is reduced by means of different bounding volumes and careful choice of parameters for polygonization.
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    Adaptive Volume Construction from Ultrasound Images of a Human Heart
    (The Eurographics Association, 2004) Reis, Gerd; Bertram, Martin; Lengen, Rolf H. van; Hagen, Hans; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    We present a volume modelling approach based on sequences of two-dimensional ultrasound images. Though generally applicable to arbitrary freehand ultrasound, our method is designed for the reconstruction of timevarying volumes from ultrasound images of a human heart. Since the reliability of the reconstructed data depends very much on the spatial density of ultrasound images, we apply a hierarchical modelling approach. The volume produced for each time step is represented as adaptive mesh refinement (AMR) data such that regions of low reliability in the reconstructed volume can be recognized by their coarse resolution.
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    Efficient Display of Background Objects for Virtual Endoscopy using Flexible First-Hit Ray Casting
    (The Eurographics Association, 2004) Neubauer, A.; Forster, M.; Wegenkittl, R.; Mroz, L.; Bühler, K.; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Many applications of virtual endoscopy require the display of background objects behind the semi-transparent surface of the investigated organ. This paper deals with pre-processing and visualization of background objects for virtual endoscopy. A new first-hit ray casting technique for efficient perspective iso-surfacing of arbitrarily selected objects of interest is described: Visualization is performed without the use of dedicated hardware or data structures limiting flexibility (e.g., polygonal meshes or distance fields). The speedup is gained by exploiting inter-pixel coherency and by finding a near-optimal compromise between reduction of ray-tracking distances and limitation of the administrational cost associated with this reduction. The algorithm was developed by enhancing the previously published cell-based first-hit ray casting algorithm. This paper describes the original algorithm and explains the extensions needed to achieve interactive rendering of background objects.
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    Efficient Isosurface Tracking Using Precomputed Correspondence Table
    (The Eurographics Association, 2004) Ji, Guangfeng; Shen, Han-Wei; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
    Feature tracking is a useful method for visualizing and analyzing time-varying scalar fields. It allows scientists to focus on regions of interest and track their evolution and interaction over time. To allow the user to freely explore the data set, features must be tracked in an efficient manner. In this paper, we present an efficient time-varying isosurface tracking algorithm. Unlike the previous algorithms which compute the corresponding isosurface components in the adjacent time steps by performing expensive computation at run time, our algorithm can rapidly identify corresponding isosurfaces by performing simple table lookup operations. This table, called the correspondence lookup table, can be computed at a preprocessing stage. The idea behind our approach is that the correspondence relationship can only change at critical isovalues in R3 or R4 and remains unchanged between adjacent pairs of critical isovalues. With our algorithm, isosurfaces can be tracked in an efficient manner with minimal overhead.