VisSym04: Joint Eurographics - IEEE TCVG Symposium on Visualization

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https://diglib.eg.org/handle/10.2312/401

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