VisSym01: Joint Eurographics - IEEE TCVG Symposium on Visualization

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https://diglib.eg.org/handle/10.2312/404

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Interacting with Stock Market Data in a Virtual Environment
(The Eurographics Association, 2001) Nesbitt, Keith; David S. Ebert and Jean M. Favre and Ronald Peikert
Virtual Environment technology enables new styles of user interfaces that provide multi-sensory interactions. For example, interfaces can be designed which immerse the user in a 3D space and provide multi-sensory feedback. Many information spaces are multivariate, large and abstract in nature. It has been a goal of Virtual Environments to widen the human to computer bandwidth and so assist in the interpretation of these spaces by providing models that allow the user to interact 'naturally'. One goal for this interaction may be to uncover useful patterns within the data. This paper describes a Virtual Environment system called the "Workbench" and explains three models of stock market data that have been developed for this environment. The aim of this work is to provide models that allow analysts to explore for new trading patterns in the stock market data. Some early results of this work are discussed.
Voxel Column Culling: Occlusion Culling for Large Terrain Models
(The Eurographics Association, 2001) Zaugg, Brian; Egbert, Parris K.; David S. Ebert and Jean M. Favre and Ronald Peikert
We present Voxel Column Culling, an occlusion culling algorithm for real-time rendering of large terrain models. This technique can greatly reduce the number of polygons that must be rendered every frame, allowing a larger piece of terrain to be rendered at an interactive frame-rate. This is accomplished by using a form of 3D cell-based occlusion culling. A visibility table for the terrain model is precomputed and stored on disk. This table is then used to quickly bypass portions of the model that are not visible due to self-occlusion of the terrain model. This technique improves performance of real-time terrain simulations by reducing the number of polygons to be rendered.
Progressive View-Dependent Isosurface Propagation
(The Eurographics Association, 2001) Liu, Zhiyan; Finkelstein, Adam; Li, Kai; David S. Ebert and Jean M. Favre and Ronald Peikert
This paper proposes a new isosurface extraction algorithm that extracts portions of the isosurface in a view-dependent manner by ray casting and propagation. The algorithm casts rays through a volume to find visible active cells as seeds and then propagates their polygonal isosurface into the neighboring cells. Small pieces of the isosurface are generated by distance-limited propagation and joined together to form the final surface. We demonstrate that this progressive algorithm generates an approximate result quickly and refines it to the final correct image over time. In addition, the algorithm scales with the resolution of the display and supports adaptive-resolution visualization.
Space-Efficient Boundary Representation of Volumetric Objects
(The Eurographics Association, 2001) Mroz, Lukas; Hauser, Helwig; David S. Ebert and Jean M. Favre and Ronald Peikert
In this paper we present a compression technique for efficiently representing boundary objects from volumetric data-sets. Exploiting spatial coherency within object contours, we are able to reduce the size of the volumetric boundary down to the size of just a few images. Allowing for direct volume rendering of the down-scaled data in addition to compression ratios up to 250:1, interactive volume visualization becomes possible, even over the Internet and on low-end hardware.
Volume Rendering Data with Uncertainty Information
(The Eurographics Association, 2001) Djurcilov, Suzana; Kim, Kwansik; Lermusiaux, Pierre F. J.; Pang, Alex; David S. Ebert and Jean M. Favre and Ronald Peikert
This paper explores two general methods for incorporating volumetric uncertainty information in direct volume rendering. The goal is to produce volume rendered images that depict regions of high (or low) uncertainty in the data. The first method involves incorporating the uncertainty information directly into the volume rendering equation. The second method involves post-processing information of volume rendered images to composite uncertainty information. We present some initial findings on what mappings provide qualitatively satisfactory results and what mappings do not. Results are considered satisfactory if the user can identify regions of high or low uncertainty in the rendered image. We also discuss the advantages and disadvantages of both approaches.
Extraction of Crack-free Isosurfaces from Adaptive Mesh Refinement Data
(The Eurographics Association, 2001) Weber, Gunther H.; Kreylos, Oliver; Ligocki, Terry J.; Shalf, John M.; Hagen, Hans; Hamann, Bernd; Joy, Kenneth I.; David S. Ebert and Jean M. Favre and Ronald Peikert
Adaptive mesh refinement (AMR) is a numerical simulation technique used in computational fluid dynamics (CFD). It permits the efficient simulation of phenomena characterized by substantially varying scales in complexity of local behavior of certain variables. By using a set of nested grids at different resolutions, AMR combines the simplicity of structured rectilinear grids with the possibility to adapt to local changes in complexity and spatial resolution. Hierarchical representations of scientific data pose challenges when isosurfaces are extracted. Cracks can arise at the boundaries between regions represented at different resolutions. We present a method for the extraction of isosurfaces from AMR data that avoids cracks at the boundaries between levels of different resolution.
Visualization of Generalized Voronoi Diagrams
(The Eurographics Association, 2001) Telea, Alexandru; Wijk, Jarke J. van; David S. Ebert and Jean M. Favre and Ronald Peikert
Voronoi diagrams are an important data structure in computer science. However well studied mathematically, understanding such diagrams for different metrics, orders, and site shapes is a complex task. We propose a new method to visualize k-order diagrams and give an efficient adaptive implementation for this method. The algorithm is easy to customize for different metrics and site shapes. Its real-time performance makes it suitable for interactive planning and analysis of complex Voronoi configurations in 2D.We illustrate the method for different combinations of metrics and site shapes.
Salient Representation of Volume Data
(The Eurographics Association, 2001) Hladuvka, Jiri; König, Andreas; Gröller, Eduard; David S. Ebert and Jean M. Favre and Ronald Peikert
We introduce a novel method for identification of objects of interest in volume data. Our approach conveys the information contained in two essentially different concepts, the object s boundaries and the narrow solid structures, in an easy and uniform way. The second order derivative operators in directions reaching minimal response are employed for this task. To show the superior performance of our method, we provide a comparison with its main competitor surface extraction from areas of maximal gradient magnitude. We show that our approach provides the possibility to represent volume data by a subset of a nominal size.
Visualization of directed associations in e-commerce transaction data
(The Eurographics Association, 2001) Hao, Ming C.; Dayal, Umeshwar; Hsu, Meichun; Sprenger, Thomas; Gross, Markus H.; David S. Ebert and Jean M. Favre and Ronald Peikert
Many real-world e-commerce applications require the mining of large volumes of transaction data to extract marketing and sales information. This paper describes the Directed Association Visualization (DAV) system that visually associates product affinities and relationships for large volumes of e-commerce transaction data. DAV maps transaction data items and their relationships to vertices, edges, and positions on a visual spherical surface. DAV encompasses several innovative techniques (1) items are positioned according to their associations to show the strength of their relationships; (2) edges with arrows are used to represent the implication directions; (3) a mass-spring engine is integrated into a visual data mining platform to provide a self-organized graph. We have applied this system successfully to market basket analysis and e-customer profiling Internet applications.
A Hardware-Assisted Visibility-Ordering Algorithm With Applications To Volume Rendering
(The Eurographics Association, 2001) Krishnan, Shankar; Silva, Cláudio T.; Wei, Bin; David S. Ebert and Jean M. Favre and Ronald Peikert
We propose a hardware-assisted visibility ordering algorithm. From a given viewpoint, a (back-to-front) visibility ordering of a set of objects is a partial order on the objects such that if object A obstructs object B, then B precedes A in the ordering. Such orderings are useful because they are the building blocks of other rendering algorithms such as direct volume rendering of unstructured grids. The traditional way to compute the visibility order is to build a set of visibility relations (e.g., B < p A), and then run a topological sort on the set of relations to actually get the partial ordering. Our technique instead works by assigning a layer number to each primitive, which directly determines the visibility ordering. Objects that have the same layer number are independent, and have no obstruction between each other. We use a simple technique which exploits a combination of the z- and stencil buffers to compute the layer number of each primitive. One application of our technique is to obtain a fast unstructured volume rendering algorithm. In this paper, we present our technique and its implementation in OpenGL. We also discuss its performance and some optimizations on some recent graphics hardware architectures.
Automotive Soiling Simulation Based On Massive Particle Tracing
(The Eurographics Association, 2001) Roettger, Stefan; Schulz, Martin; Bartelheimer, Wolf; Ertl, Thomas; David S. Ebert and Jean M. Favre and Ronald Peikert
In the automotive industry Lattice-Boltzmann type flow solvers like PowerFlow from Exa Corporation are becoming increasingly important. In contrast to the traditional finite volume approach PowerFlow utilizes a hierachical cartesian grid for flow simulation. In this case study we show how to take advantage of these hierarchical grids in order to extend an existing Lattice-Boltzmann CFD environment with an automotive soiling simulation system. To achieve this, we chose to constantly generate a huge number of massive particles in user manipulable particle emitters. The process of tracing these particles step by step thus creates evolving particle streams, which can be displayed interactively by our visualization system. Each particle is created with stochastically varying diameter, specific mass and initial velocity, whereas already existing particles may decay because of aging, when leaving the simulation domain or when colliding with the vehicle s surface. On the one hand the display of these animated particles is a very natural and intuitive way to explore a CFD data set. On the other hand animated massive particles can be easily utilized for driving an automotive soiling simulation just by coloring the particles hit points on the vehicle s surface.
Vector and Tensor Field Topology Simplification on Irregular Grids
(The Eurographics Association, 2001) Tricoche, Xavier; Scheuermann, Gerik; Hagen, Hans; Clauss, Stefan; David S. Ebert and Jean M. Favre and Ronald Peikert
Topology-based visualization of planar turbulent flows results in visual clutter due to the presence of numerous features of very small scale. In this paper, we attack this problem with a topology simplification method for vector and tensor fields defined on irregular grids. This is the generalization of previous work dealing with structured grids. The method works for all interpolation schemes.
Comparative Visualization of Instabilities in Crash-Worthiness Simulations
(The Eurographics Association, 2001) Sommer, Ove; Ertl, Thomas; David S. Ebert and Jean M. Favre and Ronald Peikert
Since crash-worthiness simulations get more and more important as part of the car development process in order to reduce the cost of development, enhance the product quality, and minimize the time-to-market, the reliability of the simulation results plays a decisive role concerning their significance. Recently the simulation departments of several automotive companies started investigating the quantity and reason for deviations during a number of simulation runs on the same input model. In this case study we discuss different measurements for instability and present a texture-based visualization method which allows the engineers to efficiently explore the simulation results by interactively hiding finite element structures with nearly constant crash performance. Furthermore, we describe those parts of our prototype which use a CORBA layer for providing the same view on a set of simulation results and allowing the visual comparison by using the marker functionality.
DDDiver: 3D Interactive Visualization of Entity Relationships
(The Eurographics Association, 2001) Coomans, Marc; Timmermans, Harry; David S. Ebert and Jean M. Favre and Ronald Peikert
In this paper we present DDDiver, a tool for the interactive visualization and editing of Object-Oriented databases. It was developed to visualize and manipulate large loosely-structured data sets with multiple relation types. This makes the tool especially useful in application areas that involve product data models, design information systems, and semantic networks. DDDiver can visualize such relational data sets in a 3d graph. The layout mechanism used for the graph is not based on a deterministic mathematical algorithm, but on the distinction between a number of relation kinds, and on user interaction. The intuitiveness and quickness of the visualization tool was further improved by adding animated visual feedback effects.
Stream Surface Generation for Fluid Flow Solutions on Curvilinear Grids
(The Eurographics Association, 2001) Gelder, Allen Van; David S. Ebert and Jean M. Favre and Ronald Peikert
A stream surface in a steady-state three-dimensional fluid flow vector field is a surface across which there is no flow. Stream surfaces can be useful for visualization because the amount of data presented in one visualization can be confined to a manageable quantity in a physically meaningful way. This paper describes a method for generation of stream surfaces, given a threedimensional vector field defined on a curvilinear grid. The method can be characterized as semi-global; that is, it tries to find a surface that satisfies constraints over a region, expressed as integrals (actually sums, due to discreteness), rather than locally propagating the solution of a differential equation. The solution is formulated as a series of quadratic minimization problems in n variables, where n is the cross-wind resolution of the grid. An efficient solution method is developed that exploits the fact that the matrix of each quadratic form is tridiagonal and symmetric. Significant numerical issues are addressed, including degeneracies in the tridiagonal matrix and degeneracies in the grid, both of which are typical for the applications envisioned.
Virtual Colon Flattening
(The Eurographics Association, 2001) Bartroli, A. Vilanova; R.Wegenkittl,; König, A.; Gröller, E.; Sorantin, E.; David S. Ebert and Jean M. Favre and Ronald Peikert
We present a new method to visualize virtual endoscopic views. We propose to flatten the organ by the direct projection of the surface onto a set of cylinders. Two sampling strategies are presented and the introduced distortions are studied. A non-photorealistic technique is presented to enhance the perception of the images. Finally, an approximate but real-time endoscopic fly-through is possible by using the data obtained by the projection technique.
Topology-Based Visualization of Time-Dependent 2D Vector Fields
(The Eurographics Association, 2001) Tricoche, Xavier; Scheuermann, Gerik; Hagen, Hans; David S. Ebert and Jean M. Favre and Ronald Peikert
Topology-based methods have been successfully applied to the visualization of instantaneous planar vector fields. In this paper, we present the topology-based visualization of time-dependent 2D flows. Our method tracks critical points over time precisely. The detection and classification of bifurcations delivers the topological structure of time dependent vector fields. This offers a general framework for the qualitative analysis and visualization of parameterdependent 2D vector fields.
Acquisition and Display of Real-Time Atmospheric Data on Terrain
(The Eurographics Association, 2001) Jiang, Tian-yue; Ribarsky, William; Wasilewski, Tony; Faust, Nickolas; Hannigan, Brendan; Parry, Mitchell; David S. Ebert and Jean M. Favre and Ronald Peikert
This paper investigates the integrated acquisition, organization, and display of data from disparate sources, including the display of data acquired in real-time. In this case real-time acquisition and display refers to the capture and visualization of data as they are being produced. The particular application investigated is 3D dynamic atmospheric data on terrain, but key elements presented here are applicable more generally to other types of real-time data. 3D Doppler radar data are acquired and visualized with global, high resolution terrain. This is the first time such data have been displayed together in a real-time environment and provides the potential for new vistas in forecasting and analysis. Associated data such as buildings and maps are displayed along with the weather data and the terrain. A global hierarchical structure makes these disparate data available for integrated visualization in real-time. Requirements for effective 3D visualization for decision-making are identified, and it is shown that the applications presented meet most of these requirements.
Interactive and Multi-modal Visualization for Neuroendoscopic Interventions
(The Eurographics Association, 2001) Bartz, Dirk; Straßer, Wolfgang; Gürvit, Özlem; Freudenstein, Dirk; Skalej, Martin; David S. Ebert and Jean M. Favre and Ronald Peikert
Based on the VIVENDI-framework for virtual endoscopy, we present a system for the interactive and multi-modal representation of important anatomical structures for neuroendoscopic interventions. A serious problem of neuroendoscopic interventions is the possibility of injuring a blood vessel while performing endoscopic surgery inside the human brain. Besides the sudden loss of optical visibility due to the red-out of the injured vessel, a potential lethal mass bleeding can be the fatal outcome of the intervention. To avoid accidental lesions, we represent the relevant information using multiple volumetric MRI-based representations of the respective organs.
Adaptive Volume Rendering using Fuzzy Logic Control
(The Eurographics Association, 2001) Li, Xinyue; Shen, Han-Wei; David S. Ebert and Jean M. Favre and Ronald Peikert
This paper presents an automatic error tolerance specification system to control the performance of hierarchical volume rendering. Rather than requiring the user to provide an explicit error tolerance numerically, we let the user to specify only the target rendering speed. Our system can then calculate an appropriate error tolerance adaptively to satisfy the user s performance goal. The system is realized using fuzzy logic control, which enables run-time adaptation based on iterative feedback control and knowledge acquired from past experience. We describe the process of constructing the fuzzy logic control system, and show that the system can successfully steer the performance of volume rendering.

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