VisSym04: Joint Eurographics - IEEE TCVG Symposium on Visualization

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

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