VisSym02: Joint Eurographics - IEEE TCVG Symposium on Visualization
Permanent URI for this collection
Parallel and Out-of-core View-dependent Isocontour Visualization Using Random Data Distribution
[meta data] [files:
Zhang, Xiaoyu
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Bajaj, Chandrajit
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Ramachandran, Vijaya
STATISTICAL COMPUTATION OF SALIENT ISO-VALUES
[meta data] [files:
Tenginakai, Shivaraj
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Machiraju, Raghu
Adding a scalar value to texture-based vector field representations by local contrast analysis
[meta data] [files:
Sanna, A.
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Zunino, C.
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Montrucchio, B.
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Montuschi, P.
Interactive Visualization and Steering of CFD Simulations
[meta data] [files:
Kreylos, O.
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Tesdall, A. M.
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Hamanny, B.
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Hunter, J. K.
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Joy, K. I.
AUFLIC: An Accelerated Algorithm For Unsteady Flow Line Integral Convolution
[meta data] [files:
Liu, ZhanPing
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II, Robert James Moorhead
Octreemizer: A Hierarchical Approach for Interactive Roaming Through Very Large Volumes
[meta data] [files:
Plate, John
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Tirtasana, Michael
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Carmona, Rhadamés
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Fröhlich, Bernd
Comparison of Morphological Pyramids for Multiresolution MIP Volume Rendering
[meta data] [files:
Roerdink, Jos B.T.M.
Shear-Warp Deluxe: The Shear-Warp Algorithm Revisited
[meta data] [files:
Sweeney, Jon
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Mueller, Klaus
Cell-Based First-Hit Ray Casting
[meta data] [files:
Neubauer, A.
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Mroz, L.
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Hauser, H.
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Wegenkittl, R.
Interactive Previewing for Transfer Function Specification in Volume Rendering
[meta data] [files:
Botha, Charl P.
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Post, Frits H.
A Generic Solution for Hardware-Accelerated Remote Visualization
[meta data] [files:
Stegmaier, Simon
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Magallón, Marcelo
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Ertl, Thomas
Feature-Preserving Volume Filtering
[meta data] [files:
Neumann, László
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Csébfalvi, Balázs
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Viola, Ivan
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Mlejnek, Matej
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Gröller, Eduard
View-Dependent Multiresolution Splatting of Non-Uniform Data
[meta data] [files:
Jang, Justin
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Ribarsky, William
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Shaw, Christopher D.
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Faust, Nickolas
Direct Volume Rendering of Photographic Volumes Using Multi-Dimensional Color-Based Transfer Functions
[meta data] [files:
Morris, Christopher J.
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Ebert, David
Best Quadratic Spline Approximation for Hierarchical Visualization
[meta data] [files:
Wiley, D. F.
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Childs, H. R.
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Hamann, B.
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Joy, K. I.
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Max, N. L.
A Continuous Skeletonization Method Based on Level Sets
[meta data] [files:
Rumpf, Martin
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Telea, Alexandru
Secondary Task Display Attributes - Optimizing Visualizations for Cognitive Task Suitability and Interference Avoidance
[meta data] [files:
Chewar, C. M.
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McCrickard, D. Scott
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Ndiwalana, Ali
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North, Chris
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Pryor, Jon
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Tessendorf, David
Visualization of Bibliographic Networks with a Reshaped Landscape Metaphor
[meta data] [files:
Brandes, U.
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Willhalm, T.
Visualizing and Investigating Multidimensional Functions
[meta data] [files:
Santos, S. R. dos
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Brodlie, K. W.
Viewpoint Entropy: A New Tool for Obtaining Good Views of Molecules
[meta data] [files:
Vázquez, Pere-Pau
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Feixas, Miquel
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Sbert, Mateu
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Llobet, Antoni
Volume Rendering Multivariate Data to Visualize Meteorological Simulations: A Case Study
[meta data] [files:
Kniss, Joe
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Hansen, Charles
Useful Properties of Semantic Depth of Field for Better F+C Visualization
[meta data] [files:
Kosara, Robert
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Miksch, Silvia
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Hauser, Helwig
Visualization of Large Web Access Data Sets
[meta data] [files:
Hao, Ming C.
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Garg, Pankaj
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Dayal, Umeshwar
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Machiraju, Vijay
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Cotting, Daniel
Speech and Gesture Multimodal Control of a Whole Earth 3D Visualization Environment
[meta data] [files:
Krum, David M.
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Omoteso, Olugbenga
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Ribarsky, William
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Starner, Thad
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Hodges, Larry F.
An Evaluation of Information Visualization in Attention-Limited Environments
[meta data] [files:
Somervell, Jacob
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McCrickard, D. Scott
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North, Chris
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Shukla, Maulik
A Novel Approach To Vortex Core Region Detection
[meta data] [files:
Jiang, Ming
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Machiraju, Raghu
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Thompson, David
Locating Closed Streamlines in 3D Vector Fields
[meta data] [files:
Wischgoll, Thomas
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Scheuermann, Gerik
An Open Toolkit for Prototyping Reverse Engineering Visualizations
[meta data] [files:
Telea, Alexandru
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Maccari, Alessandro
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Riva, Claudio
An Augmented Fast Marching Method for Computing Skeletons and Centerlines
[meta data] [files:
Telea, Alexandru
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Wijk, Jarke J. van
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Recent Submissions
Item Parallel and Out-of-core View-dependent Isocontour Visualization Using Random Data Distribution(The Eurographics Association, 2002) Zhang, Xiaoyu; Bajaj, Chandrajit; Ramachandran, Vijaya; D. Ebert and P. Brunet and I. NavazoIn this paper we describe a parallel and out-of-core view-dependent isocontour visualization algorithm that efficiently extracts and renders the visible portions of an isosurface from large datasets. The algorithm first creates an occlusion map using ray-casting and nearest neighbors. With the occlusion map constructed, the visible portion of the isosurface is extracted and rendered. All steps are in a single pass with minimal communication overhead. The overall workload is well balanced among parallel processors using random data distribution. Volumetric datasets are statically partitioned onto the local disks of each processor and loaded only when necessary. This out-of-core feature allows it to handle scalably large datasets. We additionally demonstrate significant speedup of the view-dependent isocontour visualization on a commodity off-the-shelf PC cluster.Item STATISTICAL COMPUTATION OF SALIENT ISO-VALUES(The Eurographics Association, 2002) Tenginakai, Shivaraj; Machiraju, Raghu; D. Ebert and P. Brunet and I. NavazoDetection of the salient iso-values in a volume dataset is often the first step towards its exploration. An error-and-trail approach is often used; new semi-automatic techniques either make assumptions about their data [4] or present multiple criteria for analysis. Determining if a dataset satisfies an algorithm s assumptions, or the criteria to be used in an analysis are both non-trivial tasks. The use of a dataset s statistical signatures, local higher order moments (LHOMs), to characterize its salient iso-values was presented in [10]. In this paper we propose a computational algorithm that uses LHOMs for expedient estimation of salient iso-values. As LHOMs are model independent statistical signatures our algorithm does not impose any assumptions on the data. Further, the algorithm has a single criterion for characterization of the salient iso-values, and the search for this criterion is easily automated. Examples from medical and computational domains are used to demonstrate the effectiveness of the proposed algorithm.Item Adding a scalar value to texture-based vector field representations by local contrast analysis(The Eurographics Association, 2002) Sanna, A.; Zunino, C.; Montrucchio, B.; Montuschi, P.; D. Ebert and P. Brunet and I. NavazoSeveral algorithms can effectively represent vector fields by texture-based representations, visualizing at most all information on the field: direction, orientation, and local magnitude. An open problem still remains the mapping on textures of adjunctive information such as temperature, pressure, and so on, without using colors. This article addresses this issue by proposing a technique to add a scalar value denoting streamlines by means of different levels of contrast. Both streamline starting tones and the range of tones depend on the scalar value to be mapped; in this way, areas visualized by different contrast levels are represented. Two examples show the effectiveness of the proposed technique.Item Interactive Visualization and Steering of CFD Simulations(The Eurographics Association, 2002) Kreylos, O.; Tesdall, A. M.; Hamanny, B.; Hunter, J. K.; Joy, K. I.; D. Ebert and P. Brunet and I. NavazoWe describe a system that supports real-time interactive visualization of computational fluid dynamics (CFD) simulations. The system allows a user to place and manipulate visualization primitives, such as isolines and streamlines, during an ongoing simulation process. A user can interactively select and designate regions of the computational mesh for refinement as the simulation progresses, perform remeshing, and see the effects of the refinement on the simulation in real time. The system is being used for the study of two open problems in compressible fluid dynamics. We can interactively explore solutions as they are computed, identify flow field regions containing features of interest, and refine the grid in those regions in order to obtain a better result locally. The ability to visualize "live" data, and to make changes to the computational setup in real time, has helped us to understand the underlying fundamental CFD simulation issues of these problems in shorter times than would otherwise have been possible.Item AUFLIC: An Accelerated Algorithm For Unsteady Flow Line Integral Convolution(The Eurographics Association, 2002) Liu, ZhanPing; II, Robert James Moorhead; D. Ebert and P. Brunet and I. NavazoUFLIC (Unsteady Flow Line Integral Convolution) is an effective texture synthesis technique to visualize unsteady flow with enhanced temporal coherence, but it is time-consuming to generate. This paper presents an accelerated algorithm, called AUFLIC (Accelerated UFLIC), to speed up the UFLIC generation. Our algorithm saves, re-uses, and updates pathlines in the value scattering processes. A flexible seeding strategy is introduced so that a seed particle may be directly extracted from the previous scattering processes to make best use of the saved pathline so as to reduce computationally expensive pathline integration calculations. A dynamic activation-deactivation scheme is employed to maintain the fewest necessary pathlines. Avoiding excessive pathlines achieves acceleration and nearly-constant memory consumption. With very low memory cost, AUFLIC cuts UFLIC generation time nearly in half without any image quality degradation.Item Octreemizer: A Hierarchical Approach for Interactive Roaming Through Very Large Volumes(The Eurographics Association, 2002) Plate, John; Tirtasana, Michael; Carmona, Rhadamés; Fröhlich, Bernd; D. Ebert and P. Brunet and I. NavazoWe have developed a hierarchical paging scheme for handling very large volumetric data sets at interactive frame rates. Our system trades texture resolution for speed and uses effective prediction strategies. We have tested our approach for datasets with up to 16GB in size and show that it works well with less than 500MB of main memory cache for 64MB of 3D-texture memory. Our approach makes it feasible to deal with these volumes on desktop machines.Item Comparison of Morphological Pyramids for Multiresolution MIP Volume Rendering(The Eurographics Association, 2002) Roerdink, Jos B.T.M.; D. Ebert and P. Brunet and I. NavazoWe recently proposed a multiresolution representation for maximum intensity projection (MIP) volume rendering based on morphological adjunction pyramids which allow progressive refinement and have the property of perfect reconstruction. In this algorithm the pyramidal analysis and synthesis operators are composed of morphological erosion and dilation, combined with dyadic downsampling for analysis and dyadic upsampling for synthesis. Here we introduce an alternative pyramid scheme in which a morphological opening instead of an erosion is used for pyramidal analysis. As a result, the approximation accuracy when rendering from higher levels of the pyramid is improved.Item Shear-Warp Deluxe: The Shear-Warp Algorithm Revisited(The Eurographics Association, 2002) Sweeney, Jon; Mueller, Klaus; D. Ebert and P. Brunet and I. NavazoDespite continued advances in volume rendering technology, the Shear-Warp algorithm, although conceived as early as 1994, still remains the world s fastest purely software-based volume rendering algorithm. The impressive speed of near double-digit framerates for moderately sized datasets, however, does come at the price of reduced image quality and memory consumption. In this paper, we present the implementation and impact of certain measures that seek to address these shortcomings. Specifically, we investigate the effects of: (i) post-interpolated classification and shading, (ii) matched volume sampling on zoom, (iii) the interpolation of intermediate slices to reduce inter-slice aliasing, and (iv) the re-use of encoded RLE runs for more than one major viewing direction to preserve memory. We also study a new variation of the shear-warp algorithm that operates on body-centered cubic grids. We find that the reduction of the number of voxels that this grid affords translates into direct savings in rendering times, with minimal degradation in image quality.Item Cell-Based First-Hit Ray Casting(The Eurographics Association, 2002) Neubauer, A.; Mroz, L.; Hauser, H.; Wegenkittl, R.; D. Ebert and P. Brunet and I. NavazoCell-based first-hit ray casting is a new technique for fast perspective volume visualization. This technique, based on the well known ray casting algorithm, performs iso-surfacing and supports interactive threshold adjustment. It is accelerated by the reduction of average ray path lengths to only a few steps per pixel. The volume is divided into cubic sub volumes. Each sub volume that is intersected by an iso-surface is projected to the image plane. A local ray casting step within the sub volume is performed for each pixel covered by the projection. Cell-based first-hit ray casting is perfectly suited whenever fast perspective iso-surfacing is required. This paper describes the basic algorithm, presents possible optimizations and evaluates the performance of the algorithm for one specific application, the post-implantation assessment of endovascular stent placement. It will be shown that the algorithm, though executed on a single processor machine without any hardware acceleration, performs well for view points inside as well as outside the stented blood vessel and significantly outperforms an optimized, yet more conventional ray casting technique.Item Interactive Previewing for Transfer Function Specification in Volume Rendering(The Eurographics Association, 2002) Botha, Charl P.; Post, Frits H.; D. Ebert and P. Brunet and I. NavazoThis paper presents a new technique for supplying meaningful visual feedback during direct volume rendering transfer function specification. The technique uses meta-data calculated during a pre-processing step to generate interactively an approximate volume rendering that is voxel-registered with a single user-selected slice. Because of the registration, this preview can easily be alpha-blended with a grey-scale image of the data that is being volume rendered. In this way, the user gets real-time visual feedback on her transfer function specification with regards to both the expected composited optical properties and the "fidelity" (how closely the rendering matches the original data) of the resulting rendering.Item A Generic Solution for Hardware-Accelerated Remote Visualization(The Eurographics Association, 2002) Stegmaier, Simon; Magallón, Marcelo; Ertl, Thomas; D. Ebert and P. Brunet and I. NavazoThis paper presents a generic solution for hardware-accelerated remote visualization that works transparently for all OpenGL-based applications and OpenGL-based scene graphs. Universality is achieved by taking advantage of dynamic linking, efficient data transfer by means of VNC. The proposed solution does not require any modifications of existing applications and allows for remote visualization with different hardware architectures involved in the visualization process. The library s performance is evaluated using standard OpenGL example programs and by volume rendering substantial data sets.Item Feature-Preserving Volume Filtering(The Eurographics Association, 2002) Neumann, László; Csébfalvi, Balázs; Viola, Ivan; Mlejnek, Matej; Gröller, Eduard; D. Ebert and P. Brunet and I. NavazoIn this paper a feature-preserving volume filtering method is presented. The basic idea is to minimize a threecomponent global error function penalizing the density and gradient errors and the curvature of the unknown filtered function. The optimization problem leads to a large linear equation system defined by a sparse coefficient matrix. We will show that such an equation system can be efficiently solved in frequency domain using fast Fourier transformation (FFT). For the sake of clarity, first we illustrate our method on a 2D example which is a dedithering problem. Afterwards the 3D extension is discussed in detail since we propose our method mainly for volume filtering. We will show that the 3D version can be efficiently used for elimination of the typical staircase artifacts of direct volume rendering without losing fine details. Unlike local filtering techniques, our novel approach ensures a global smoothing effect. Previous global 3D methods are restricted to binary volumes or segmented iso-surfaces and they are based on area minimization of one single reconstructed surface. In contrast, our method is a general volume-filtering technique, implicitly smoothing all the iso-surfaces at the same time. Although the strength of the presented algorithm is demonstrated on a specific 2D and a specific 3D application, it is considered as a general mathematical tool for processing images and volumes.Item View-Dependent Multiresolution Splatting of Non-Uniform Data(The Eurographics Association, 2002) Jang, Justin; Ribarsky, William; Shaw, Christopher D.; Faust, Nickolas; D. Ebert and P. Brunet and I. NavazoThis paper develops an approach for the splat-based visualization of large scale, non-uniform data. A hierarchical structure is generated that permits detailed treatment at the leaf nodes of the non-uniform distribution. A set of levels of detail (LODs) are generated based on the levels of the hierarchy. These yield two metrics, one in terms of the spatial extent of the bounding box containing the splat and one in terms of the variation of the scalar field over this box. The former yields a view-dependent choice of LODs while the latter yields a view-independent LOD based on the field variation. To show the utility of this general approach it is applied to a set of application data for a whole earth environment and some test data. Performance results are given.Item Direct Volume Rendering of Photographic Volumes Using Multi-Dimensional Color-Based Transfer Functions(The Eurographics Association, 2002) Morris, Christopher J.; Ebert, David; D. Ebert and P. Brunet and I. NavazoTraditionally, volume rendering of medical data has been comprised of transfer functions that map a scalar value, usually a MRI or CT intensity, to an opacity. Corresponding color maps are either selected regardless of the actual physical color of the volume (i.e. greyscale) or predetermined as in photographic volumes. Rarely has the voxel color been used as a means to define the associated opacity value. By using transfer functions that map multichannel color values(RGB or CIE L¤u¤v¤) to opacity, we can generate compelling and informative renderings that provide consistent boundary extraction throughout the volume. We present renderings of the Visible Human photographic volume using multi-dimensional color-based transfer functions. These functions were constructed by using gradient boundary enhancement techniques in conjunction with volume illustration techniques and incorporating the first and second directional derivatives along the gradient direction. We empirically compare the effectiveness of using the color-based transfer functions and discuss their applications and potential for future development.Item Best Quadratic Spline Approximation for Hierarchical Visualization(The Eurographics Association, 2002) Wiley, D. F.; Childs, H. R.; Hamann, B.; Joy, K. I.; Max, N. L.; D. Ebert and P. Brunet and I. NavazoWe present a method for hierarchical data approximation using quadratic simplicial elements for domain decomposition and field approximation. Higher-order simplicial elements can approximate data better than linear elements. Thus, fewer quadratic elements are required to achieve similar approximation quality. We use quadratic basis functions and compute best quadratic simplicial spline approximations that are C0-continuous everywhere. We adaptively refine a simplicial approximation by identifying and bisecting simplicial elements with largest errors. It is possible to store multiple approximation levels of increasing quality. We have tested the suitability and efficiency of our hierarchical data approximation scheme by applying it to several data sets.Item A Continuous Skeletonization Method Based on Level Sets(The Eurographics Association, 2002) Rumpf, Martin; Telea, Alexandru; D. Ebert and P. Brunet and I. NavazoA robust and efficient method in 2D and 3D for the calculation of skeletons for arbitrary objects is presented. The method is based on the calculation of the distance function with respect to the object boundary. This is combined, in a post processing step, with a new indicator to identify the skeleton, which coincides with the singularity set of the distance map. The indicator is defined as a suitable function of certain local momenta of this distance map and allows a robust and accurate computation of the distance from the skeleton set. This distance is then extended, again via the level set method, onto the whole space. Several applications in 2D and 3D are presented.Item Bag-of-Particles as a Deformable Model(The Eurographics Association, 2002) Stahl, D.; Ezquerra, N.; Turk, G.; D. Ebert and P. Brunet and I. NavazoWe present an interactive, physically-based, elastically deformable model using a particle system to model surfaces with interior volumes that can be haptically felt. Oriented particles used in existing surface-only models, and unoriented particles used in volume-only simulations are combined to form a bag-of-particles. Multiple species of surface and volume particles, coupled with prede£ned interspecies parameters, determine the elastic properties of a bag. Starting with an object represented as a 3D voxel bitmap of connected components, the gradient of its distance map gives a vector £eld, or gradient map, that captures the static shape of an object and provides shape-maintaining forces. The gradient map enables the user to de£ne the geometry of the simulated objects, and provides feedback reaction forces allowing a user to feel the model. A bag-of-particles model can simulate several objects in the same scene, as well as objects composed of different materials, such as organs with multiple tissue types. We demonstrate the bag-of-particles approach using a number of different data sources, and apply it to modeling myocardium dynamics.Item Secondary Task Display Attributes - Optimizing Visualizations for Cognitive Task Suitability and Interference Avoidance(The Eurographics Association, 2002) Chewar, C. M.; McCrickard, D. Scott; Ndiwalana, Ali; North, Chris; Pryor, Jon; Tessendorf, David; D. Ebert and P. Brunet and I. NavazoWe found that established display design guidelines for focal images cannot be extended to images displayed as a secondary task in a dual-task situation. This paper describes an experiment that determines a new ordering guideline for secondary task image attributes according to human cognitive ability to extract information. The imperative for alternate guidelines is based on the difference in an image s ability to convey meaning, which decreases when moved from a focal to a secondary task situation. Secondary task attribute ordering varies with the level of degradation in the primary task. Furthermore, attribute effectiveness may be particular to types of visual operations relating to cognitive tasks.Item Visualization of Bibliographic Networks with a Reshaped Landscape Metaphor(The Eurographics Association, 2002) Brandes, U.; Willhalm, T.; D. Ebert and P. Brunet and I. NavazoWe describe a novel approach to visualize bibliographic networks that facilitates the simultaneous identification of clusters (e.g., topic areas) and prominent entities (e.g., surveys or landmark papers). While employing the landscape metaphor proposed in several earlier works, we introduce new means to determine relevant parameters of the landscape. Moreover, we are able to compute prominent entities, clustering of entities, and the landscape s surface in a surprisingly simple and uniform way. The effectiveness of our network visualizations is illustrated on data from the graph drawing literature.Item Visualizing and Investigating Multidimensional Functions(The Eurographics Association, 2002) Santos, S. R. dos; Brodlie, K. W.; D. Ebert and P. Brunet and I. NavazoThis paper addresses the problem of visualizing multidimensional scalar functions. These functions are often encountered in fields such as Engineering, Mathematics, and Physics to understand and model complex phenomena. We propose a novel method based on the dimension reduction philosophy called HyperCell. Its basic concept is to represent the function by means of dynamic orthogonal low (ID, 2D, or 3D) dimensional subspaces, called Cells. Firstly the user defines a N-dimensional region of interest, in which the data can be visualized. Then the user interactively creates cells by selecting up to three dimensions from the function domain. A cell can be visualized using a standard visualization algorithm such as isosurfacing or volume rendering. The analysis of the function is done by investigating several cells, which can be sampled simultaneously at different regions of interest in N-Space. The HyperCell method allows several useful operations to help the exploratory process such as navigation and rotation in N-Space, and brushing.Item Viewpoint Entropy: A New Tool for Obtaining Good Views of Molecules(The Eurographics Association, 2002) Vázquez, Pere-Pau; Feixas, Miquel; Sbert, Mateu; Llobet, Antoni; D. Ebert and P. Brunet and I. NavazoThe computation of good viewpoints is important in several fields: computer graphics, removal of degeneracies in computational geometry, robotics, graph drawing, etc. However, in areas such as computer graphics there is no consensus on what a good viewpoint means and, consequently, each author uses his or her own definition according to the requirements of the application. In this paper we present a formal measure strongly based on Information Theory, viewpoint entropy, that can be applied to certain problems of Computer Graphics such as automatic exploration of objects or scenes and Scene Understanding. We also define a new measure, the orthogonal frustum entropy, in order to fulfill the requirements needed to visualize molecules. We design an algorithm that makes use of graphics hardware to accelerate computation, and whose complexity depends mainly on the number of views we want to analyze. Computation of good views of molecules is useful for molecular scientists, a field which includes practitioners from Crystallography, Chemistry, and Biology.Item Volume Rendering Multivariate Data to Visualize Meteorological Simulations: A Case Study(The Eurographics Association, 2002) Kniss, Joe; Hansen, Charles; D. Ebert and P. Brunet and I. NavazoHigh resolution computational weather models are becoming increasing complex. However, the analysis of these models has not benefited from recent advancements in volume visualization. This case study applies the ideas and techniques from multi-dimensional transfer function based volume rendering to the multivariate weather simulations. The specific goal of identifying frontal zones is addressed. By combining temperature and humidity as a multivariate field, the frontal zones are more readily identified thereby assisting the meteorologists in their analysis tasks.Item Useful Properties of Semantic Depth of Field for Better F+C Visualization(The Eurographics Association, 2002) Kosara, Robert; Miksch, Silvia; Hauser, Helwig; D. Ebert and P. Brunet and I. NavazoThis paper presents the results of a thorough user study that was performed to assess some features and the general usefulness of Semantic Depth of Field (SDOF). Based on these results, concrete hints are given on how SDOF can be used for visualization. SDOF was found to be a very effective means for guiding the viewer s attention and for giving him or her a quick overview of a data set. It can also very quickly be perceived, and therefore provides an efficient visual channel. Semantic Depth of Field is a focus+context (F+C) technique that uses blur to point the user to the most relevant objects. It was inspired by the depth of field (DOF) effect in photography, which serves a very similar purpose.Item Visualization of Large Web Access Data Sets(The Eurographics Association, 2002) Hao, Ming C.; Garg, Pankaj; Dayal, Umeshwar; Machiraju, Vijay; Cotting, Daniel; D. Ebert and P. Brunet and I. NavazoMany real-world e-service applications require analyzing large volumes of transaction data to extract web access information. This paper describes Web Access Visualization (WAV) a system that visually associates the affinities and relationships of clients and URLs for large volumes of web transaction data. To date, many practical research projects have shown the usefulness of a physics-based mass-spring technique to layout data items with close relationships onto a graph. The WAV system: (1) maps transaction data items (clients, URLs) and their relationships to vertices, edges, and positions on a 3D spherical surface; (2) encapsulates a physics-based engine in a visual data analysis platform; and (3) employs various content sensitive visual techniques - linked multiple views, layered drill-down, and fade in/out - for interactive data analysis. We have applied this system to a web application to analyze web access patterns and trends. The web service quality has been greatly benefited from using the information provided by WAV.Item Speech and Gesture Multimodal Control of a Whole Earth 3D Visualization Environment(The Eurographics Association, 2002) Krum, David M.; Omoteso, Olugbenga; Ribarsky, William; Starner, Thad; Hodges, Larry F.; D. Ebert and P. Brunet and I. NavazoA growing body of research shows several advantages to multimodal interfaces including increased expressiveness, flexibility, and user freedom. This paper investigates the design of such an interface that integrates speech and hand gestures. The interface has the additional property of operating relative to the user and can be used while the user is in motion or standing at a distance from the computer display. The paper then describes an implementation of the multimodal interface for a whole Earth 3D visualization which presents navigation interface challenges due to the large magnitude of scale and extended spaces that are available. The characteristics of the multimodal interface are examined, such as speed, recognizability of gestures, ease and accuracy of use, and learnability under likely conditions of use. This implementation shows that such a multimodal interface can be effective in a real environment and sets some parameters for the design and use of such interfaces.Item Vortex Tracking in Scale-Space(The Eurographics Association, 2002) Bauer, Dirk; Peikert, Ronald; D. Ebert and P. Brunet and I. NavazoScale-space techniques have become popular in computer vision for their capability to access the multiscale information inherently contained in images. We show that the field of flow visualization can benefit from these techniques, too, yielding more coherent features and sorting out numerical artifacts as well as irrelevant large-scale features. We describe an implementation of scale-space computation using finite elements and show that performance is sufficient for computing a scale-space of time-dependent CFD data. Feature tracking, if available, allows to process the information provided by scale-space not just visually but also algorithmically. We present a technique for extending a class of feature extraction schemes by an additional dimension, resulting in an efficient solution of the tracking problem.Item An Evaluation of Information Visualization in Attention-Limited Environments(The Eurographics Association, 2002) Somervell, Jacob; McCrickard, D. Scott; North, Chris; Shukla, Maulik; D. Ebert and P. Brunet and I. NavazoPeople often need to quickly access or maintain awareness of secondary information while busy with other primary tasks. Information visualizations provide rapid, effective access to information, but are generally designed to be examined by users as the primary focus of their attention. The goal of this research is to discover how to design information visualizations intended for the periphery and to understand how quickly and effectively people can interpret information visualizations while they are busily performing other tasks. We evaluated how several factors of a visualization (visual density, presence time, and secondary task type) impact people s abilities to continue with a primary task and to complete secondary tasks related to the visualization. Our results suggest that, with relaxed time pressure, reduced visual information density and a single well-defined secondary task, people can effectively interpret visualizations with minimal distraction to their primary task.Item A Novel Approach To Vortex Core Region Detection(The Eurographics Association, 2002) Jiang, Ming; Machiraju, Raghu; Thompson, David; D. Ebert and P. Brunet and I. NavazoIn this paper we present a simple and efficient vortex core region detection algorithm based on ideas derived from combinatorial topology. These ideas originated from Sperner s lemma, which by itself is of little value to detecting vortex cores. However, we take these ideas from the lemma and apply them in a point-based fashion to detecting vortex core regions. The resulting algorithms for both 2D and 3D are quite simple and very efficient compared to existing ones. We applied our algorithms to both numerically simulated and procedurally generated datasets to illustrate the efficacy of our approach.Item Locating Closed Streamlines in 3D Vector Fields(The Eurographics Association, 2002) Wischgoll, Thomas; Scheuermann, Gerik; D. Ebert and P. Brunet and I. NavazoThe analysis and visualization of flows is a central problem in visualization. Topology based methods have gained increasing interest in recent years. This article describes a method for the detection of closed streamlines in 3D flows. It is based on a special treatment of cases where a streamline reenters a cell to prevent infinite cycling during streamline calculation. The algorithm checks for possible exits of a loop of crossed faces and detects structurally stable closed streamlines. These global features are not detected by conventional topology and feature detection algorithms.Item An Open Toolkit for Prototyping Reverse Engineering Visualizations(The Eurographics Association, 2002) Telea, Alexandru; Maccari, Alessandro; Riva, Claudio; D. Ebert and P. Brunet and I. NavazoMaintenance and evolution of complex software systems (such as mobile telephones) involves activities such as reverse engineering (RE) and software visualization. Although several RE tools exist, we found their architecture hard to adapt to the domain and problem specific requirements posed by our current practice in Nokia. In this paper, we present an open architecture which allows easy prototyping of RE data exploration and visualization scenarios for a large range of domain models. We pay special attention to the visual and interactive requirements of the reverse engineering process. We compare our toolkit with other existing reverse engineering visual tools and outline the differences.Item An Augmented Fast Marching Method for Computing Skeletons and Centerlines(The Eurographics Association, 2002) Telea, Alexandru; Wijk, Jarke J. van; D. Ebert and P. Brunet and I. NavazoWe present a simple and robust method for computing skeletons for arbitrary planar objects and centerlines for 3D objects. We augment the Fast Marching Method (FMM) widely used in level set applications 11 by computing the paramterized boundary location every pixel came from during the boundary evolution. The resulting parameter field is then thresholded to produce the skeleton branches created by boundary features of a given size. The presented algorithm is straightforward to implement, has low memory costs and short execution times, and is robust with respect to the used threshold and initial shape noisiness. The produced skeletons are very similar to the ones delivered by more complex algorithms. Various 2D and 3D applications are presented.