VisSym04: Joint Eurographics - IEEE TCVG Symposium on Visualization

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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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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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