VisSym00: Joint Eurographics - IEEE TCVG Symposium on Visualization

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AlVis - An Aluminium-Foam Visualization and Investigation Tool
(The Eurographics Association, 2000) König, Andreas H.; Doleisch, Helmut; Kottar, Andreas; Kriszt, Brigitte; Gröller, Eduard; W. de Leeuw and R. van Liere
In recent years there has been an increased interest in metal foams in the field of material science. The stress absorbing potential is one of the most interesting properties for the application of aluminium foam (e.g. car manufacturing). Material scientists need to investigate the structure of metal foams in order to optimize their deformation behavior. An interactive tool for the investigation is presented in this work. Real-time surface rendering, automatic parameter determination, and display of local and global foam properties enable the user to understand the complex structure of the metal foam.
Appearance-Based Virtual-View Generation for Fly Through in a Real Dynamic Scene
(The Eurographics Association, 2000) Baba, Shigeyuki; Saito, Hideo; Vedula, Sundar; Cheung, Kong Man; Kanade, Takeo; W. de Leeuw and R. van Liere
We present appearance-based virtual view generation which allows viewers to fly through a real dynamic scene. The scene is captured by synchronized multiple cameras. Arbitrary views are generated by interpolating two original camera-view images near the given viewpoint. The quality of the generated synthetic view is determined by the precision, consistency and density of correspondences between the two images. All or most of previous work that uses interpolation extracts the correspondences from these two images. However, not only is it difficult to do so reliably (the task requires a good stereo algorithm), but also the two images alone sometimes do not have enough information, due to problems such as occlusion. Instead, we take advantage of the fact that we have many views, from which we can extract much more reliable and comprehensive 3D geometry of the scene as a 3D model. The dense and precise correspondences between the two images, to be used for interpolation, are derived from this constructed 3D model. Our method of 3D modeling from multiple images uses the Multiple Baseline Stereo method and Shape from Silhouette method.
A Case Study of Isosurface Extraction Algorithm Performance
(The Eurographics Association, 2000) Sutton, Philip M.; Hansen, Charles D.; Shen, Han-Wei; Schikore, Dan; W. de Leeuw and R. van Liere
Isosurface extraction is an important and useful visualization method. Over the past ten years, the field has seen numerous isosurface techniques published, leaving the user in a quandary about which one should be used. Some papers have published complexity analysis of the techniques, yet empirical evidence comparing different methods is lacking. This case study presents a comparative study of several representative isosurface extraction algorithms. It reports and analyzes empirical measurements of execution times and memory behavior for each algorithm. The results show that asymptotically optimal techniques may not be the best choice when implemented on modern computer architectures.
Case Study: Resource Steering in a Visualization System
(The Eurographics Association, 2000) Chi, Ed H.; Riedl, John T.; W. de Leeuw and R. van Liere
Visual computational steering environments extend traditional visualization environments by enabling the user to interactively steer the computations applied to the data. In this paper, we develop a new type of computational steering. Resource steering extends current visual steering techniques by providing machine resource estimation and control to the user. With resource steering, the user controls the execution of the computation on a parallel or distributed computer based on experimentally or theoretically derived estimates of the parallel performance of the computation. We demonstrate this extended steering model by applying it to an information visualization system that analyzes genetic sequence similarity reports. We show how our extended steering model enhances the user s ability to control visualization computations.
Contextual Visualization of Actor Status in Social Networks
(The Eurographics Association, 2000) Brandes, Ulrik; Wagner, Dorothea; W. de Leeuw and R. van Liere
We propose a novel information visualization approach for an analytical method applied in the social sciences. In social network analysis, social structures are formally represented as graphs, and structural properties of these graphs are assumed to be useful in the explanation of social phenomena. A particularly important such property is the relative status of actors in a given network. Since operationalizations of status are aggregate indices of vertices, researchers are not only interested in status, but also in the context leading to these values, i.e. the underlying social network. We therefore visualize the network in a layered fashion, mapping status scores to vertical coordinates. The resulting problem of determining horizontal positions of vertices such that the overall layout is readable, is algorithmically difficult, yet well-studied in the literature on graph drawing. We outline a customized approach that routinely produces satisfactory pictures at interactive speed.
DAG Drawing from an Information Visualization Perspective
(The Eurographics Association, 2000) Melancon, G.; Herman, I.; W. de Leeuw and R. van Liere
When dealing with a graph, any visualization strategy must rely on a layout procedure at least to initiate the process. Because the visualization process evolves within an interactive environment the choice of this layout procedure is critical and will often be based on efficiency. This paper compares two popular layout strategies, one based on the extraction of a spanning tree, the other based on edge crossing minimization of directed acyclic graphs. The comparison is made based on a large number of experimental evidence gathered through random graph generation. The main conclusion of these experiments is that, contrary to the popular belief, usage of edge crossing minimization algorithms may be extremely useful and advantageous, even under the heavy requirements of information visualization.
Design of Visualizations for Urban Modeling
(The Eurographics Association, 2000) Pinnel, L. Denise; Dockrey, Matthew; Brush, A.J. Bernheim; Borning, Alan; W. de Leeuw and R. van Liere
Urban planning experts often use computer models to help evaluate alternative land use policies, particularly as they interact with transportation and environmental decisions. The greatly increased data volume provided by new land use models makes their effective use difficult without suitable visualization tools. We present UrbanView, a visualization system for urban modeling, and describe a user study to determine appropriate visualizations for the urban modeling domain.
Direct Volume Rendering from Photographic Data
(The Eurographics Association, 2000) Ebert, David; McClanahan, Tim; Rheingans, Penny; Yoo, Terry; W. de Leeuw and R. van Liere
Direct volume rendering from photographic volume data has the potential to create realistic images of internal volume structure, as well as the structure of boundaries within the volume. While possession of the photographic volume simplifies color calculations in voxel illumination, it complicates opacity calculation. This paper describes a framework for addressing illumination challenges in photographic volume data and presents initial results.
Drawing Relational Schemas
(The Eurographics Association, 2000) Battista, Giuseppe Di; Didimo, Walter; Patrignani, Maurizio; Pizzonia, Maurizio; W. de Leeuw and R. van Liere
A wide number of practical applications would benefit from automatically generated graphical representations of relational schemas, in which tables are represented by boxes, and table attributes correspond to distinct stripes inside each table. Links, connecting two attributes of two different tables, represent relational constraits or join paths, and may attach arbitrarily to the left or to the right side of the stripes representing the attributes. To our knowledge no drawing technique is available to automatically produce diagrams in such strongly constrained drawing convention. In this paper we provide a polynomial time algorithm solving this problem and test its efficiency and effectiveness against a large test suite.
Dynamic Overview Techniques for Image Retrieval
(The Eurographics Association, 2000) Pu, Pearl; Pecenovic, Zoran; W. de Leeuw and R. van Liere
One difficulty often overlooked in information retrieval systems is that search criteria themselves are often poorly defined. People describe their information needs in many different ways and frequently change their goals depending on the current results of their search. We have investigated the hypothesis that overviews of the space of available solutions are a good way to remedy this situation. Our overview techniques allow users to get a feel for the meaning of categories through randomly chosen examples, find similar images using content search, and to inspect the global distribution of images according to certain criteria. Users thus organize the retrieval task into an iterative browsing process that makes them specify their queries more accurately. As a result they are more satisfied with what the system retrieves.
Fast Visualization of Special Relativistic Effects on Geometry and Illumination
(The Eurographics Association, 2000) Weiskopf, Daniel; W. de Leeuw and R. van Liere
This paper describes a novel rendering technique for the special relativistic visualization of the geometry and illumination of fast moving objects. The physical basis consists of the relativistic aberration of light, the Doppler effect, and the searchlight effect. They account for changes of apparent geometry, color, and brightness of the objects. The rendering technique makes use of modern computer graphics hardware, in particular texture mapping and advanced per-pixel operations, and allows the visualization of these important special relativistic effects at interactive frame rates.
A Framework for Interactive Hardware Accelerated Remote 3D-Visualization
(The Eurographics Association, 2000) Engel, Klaus; Sommer, Ove; Ertl, Thomas; W. de Leeuw and R. van Liere
In this paper we present a framework that provides remote control to Open Inventor or Cosmo3D based visualization applications. A visualization server distributes a visualization session to Java based clients by transmitting compressed images from the server frame buffer. Visualization parameters and GUI events from the clients are applied to the server application by sending CORBA (Common Object Request Broker Architecture) requests. The framework provides transparent access to remote visualization capabilities and allows sharing of expensive resources. Additionally the framework opens new possibilities for collaborative work and distance education. We present a teleradiology system and an automotive development application which make use of the proposed techniques.
Hardware Accelerated Wavelet Transformations
(The Eurographics Association, 2000) Hopf, Matthias; Ertl, Thomas; W. de Leeuw and R. van Liere
Wavelets and related multiscale representations are important means for edge detection and processing as well as for segmentation and registration. Due to the computational complexity of these approaches no interactive visualization of the extraction process is possible nowadays. By using the hardware of modern graphics workstations for accelerating wavelet decomposition and reconstruction we realize a first important step for removing lags in the visualization cycle.
Hierarchical Data Representations Based on Planar Voronoi Diagrams
(The Eurographics Association, 2000) Schussman, Shirley; Bertram, Martin; Hamann, Bernd; Joy, Kenneth I.; W. de Leeuw and R. van Liere
Multiresolution representation of high-dimensional scattered data is a fundamental problem in scientific visualization. This paper introduces a data hierarchy of Voronoi diagrams as a versatile solution. Given an arbitrary set of points in the plane, our goal is the construction of an approximation hierarchy using the Voronoi diagram as the essential building block. We have implemented two Voronoi diagram-based algorithms to demonstrate their usefulness for hierarchical scattered data approximation. The first algorithm uses a constant function to approximate the data within each Voronoi cell, and the second algorithm uses the Sibson interpolant [14].
Hybrid Model for Vascular Tree Structures
(The Eurographics Association, 2000) Puig, Anna; Tost, Dani; Navazo, Isabel; W. de Leeuw and R. van Liere
This paper proposes a new representation scheme of the cerebral blood vessels. This model provides information on the semantics of the vascular structure: the topological relationships between vessels and the labeling of vascular accidents such as aneurysms and stenoses. In addition, the model keeps information of the inner surface geometry as well as of the vascular map volume properties, i.e. the tissue density, the blood flow velocity and the vessel wall elasticity. The model can be constructed automatically in a pre-process from a set of segmented MRA images. Its memory requirements are optimized on the basis of the sparseness of the vascular structure. It allows fast queries and efficient traversals and navigations. The visualizations of the vessel surface can be performed at different levels of detail. The direct rendering of the volume is fast because the model provides a natural way to skip over empty data. The paper analyzes the memory requirements of the model along with the costs of the most important operations on it.
Improving Angular Resolution in Visualizations of Geographic Networks
(The Eurographics Association, 2000) Brandes, Ulrik; Shubina, Galina; Tamassia, Roberto; W. de Leeuw and R. van Liere
In visualizations of large-scale transportation and communications networks, node coordinates are usually fixed to preserve the underlying geography, while links are represented as geodesics for simplicity. This often leads to severe readability problems due to poor angular resolution, i.e. small angles formed by lines converging in a node. We present a new method using automatically routed cubic curves that both preserves node coordinates and eliminates the resolution problem. The approach is applied to representations in the plane and on the sphere, showing European train connections and Internet traffic, respectively.
Integrated Multiresolution Geometry and Texture Models for Terrain Visualization
(The Eurographics Association, 2000) Baumann, Konstantin; Döllner, Jürgen; Hinrichs, Klaus; W. de Leeuw and R. van Liere
In this paper, an approach for integrating multiresolution representations of terrain geometry and terrain texture data is presented. A terrain is modeled by a regular grid, which can be partially refined by local TINs in order to represent morphologically complex terrain parts. The multiresolution models for terrain texture data and geometry data are closely related: The rendering algorithm selects geometry and texture patches based on screen-space error criteria. Multiple texture hierarchies, which may represent different thematic information layers, can be bound to one terrain model. Multiple textures lead to a drastic improvement of visual quality: Topographic textures can be used to provide pixel-precise shading, alpha textures can be used to restrict or to highlight thematic textures. Multiple textures facilitate the development of visual interaction tools such as magic lenses, and texture animations. Multitexturing permits an efficient implementation of these concepts.
Multiresolution Techniques for Interactive Texture-based Rendering of Arbitrarily Oriented Cutting Planes
(The Eurographics Association, 2000) LaMar, Eric; Duchaineau, Mark A.; Hamann, Bernd; Joy, Kenneth I.; W. de Leeuw and R. van Liere
We present a multiresolution technique for interactive texture based rendering of arbitrarily oriented cutting planes for very large data sets. Thismethod uses an adaptive scheme that renders the data along a cutting plane at different resolutions: higher resolution near the point-of-interest and lower resolution away from the point-of-interest. The algorithm is based on the segmentation of texture space into an octree, where the leaves of the tree define the original data and the internal nodes define lower-resolution versions. Rendering is done adaptively by selecting high-resolution cells close to a center of attention and low-resolution cells away from it. We limit the artifacts introduced by this method by blending between different levels of resolution to produce a smooth image. This technique can be used to produce viewpoint-dependent renderings.
Progressive Volume Models for Rectilinear Data using Tetrahedral Coons Volumes
(The Eurographics Association, 2000) Holliday, David J.; Nielson, Gregory M.; W. de Leeuw and R. van Liere
We present a new technique for modeling rectilinear volume data. The algorithm produces a trivariate model, F(x; y; z), which is piecewise defined over tetrahedra that fits the volume data to within a user specified tolerance. The technique is adaptive leading to an efficient model that is more complex where the data demands it. The novelty of the present technique is that a valid tetrahedrization is not required. Tetrahedral cells are subdivided as required by the error condition only. This type of cellular decomposition leads to a continuous model by the use of a tetrahedral Coons volume which has the ability to interpolate to arbitrary boundary data.
Skeleton Graph Generation for Feature Shape Description
(The Eurographics Association, 2000) Reinders, Freek; Jacobson, Melvin E.D.; Post, Frits H.; W. de Leeuw and R. van Liere
An essential step in feature extraction is the calculation of attribute sets describing the characteristics of a feature. Often, attribute sets include the position, size, and orientation of the feature. These attributes are very important, but they do not provide a good approximation of the shape of a feature. For better shape description, a more sophisticated method is needed. This paper describes a method that extracts a binary skeleton of a feature, and transforms it into a graphical representation: the skeleton-graph. This graph represents the original skeleton with controlled precision, and contains the essential topology and geometry of the skeleton. In addition, distance information is used to generate a simplified reconstruction of the original 3D feature shape, which can also be used as an iconic object for visualization.

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