EuroVis06: Joint Eurographics - IEEE VGTC Symposium on Visualization

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GPU-Accelerated Volume Splatting With Elliptical RBFs

Neophytou, Neophytos
Mueller, Klaus
McDonnell, Kevin T.
Hong, Wei
Guan, Xin
Qin, Hong
Kaufman, Arie

Hardware-accelerated Extraction and Rendering of Point Set Surfaces

Tejada, E.
Gois, J. P.
Nonato, L. G.
Castelo, A.
Ertl, T.

GPU-Based Hyperstreamlines for Diffusion Tensor Imaging

Reina, G.
Bidmon, K.
Enders, F.
Hastreiter, P.
Ertl, T.

GPUFLIC: Interactive and Accurate Dense Visualization of Unsteady Flows

Li, Guo-Shi
Tricoche, Xavier
Hansen, Charles

Combining Extended Table Lens and Treemap Techniques for Visualizing Tabular Data

Telea, Alexandru

Natural Visualizations

Haroz, Steve
Ma, Kwan-Liu

Evaluating the Effectiveness of Tree Visualization Systems for Knowledge Discovery

Wang, Yue
Teoh, Soon Tee
Ma, Kwan-Liu

PhylloTrees: Phyllotactic Patterns for Tree Layout

Neumann, Petra
Carpendale, Sheelagh
Agarawala, Anand

Efficient Surface Reconstruction from Noisy Data using Regularized Membrane Potentials

Jalba, A. C.
Roerdink, J. B. T. M.

Robust Surface Detection for Variance Comparison and Dimensional Measurement

Heinzl, C.
Klingesberger, R.
Kastner, J.
Gröller, E.

Direct Isosurface Extraction from Scattered Volume Data

Rosenthal, Paul
Linsen, Lars

Knowledge-Based Out-of-Core Algorithms for Data Management in Visualization

Chisnall, David
Chen, Min
Hansen, Charles

Terrain Rendering using Spherical Clipmaps

Clasen, Malte
Hege, Hans-Christian

Volume Composition Using Eye Tracking Data

Lu, Aidong
Maciejewski, Ross
Ebert, David S.

Path Line Oriented Topology for Periodic 2D Time-Dependent Vector Fields

Shi, K.
Theisel, H.
Weinkauf, T.
Hauser, H.
Hege, H.-C.
Seidel, H.-P.

Texture Advection on Stream Surfaces: A Novel Hybrid Visualization Applied to CFD Simulation Results

Laramee, Robert S.
Garth, Christoph
Schneider, Jürgen
Hauser, Helwig

Enhancing Slice-based Visualizations of Medical Volume Data

Tietjen, Christian
Meyer, Björn
Schlechtweg, Stefan
Preim, Bernhard
Hertel, Ilka
Strauß, Gero

Segmentation of Flow Fields using Pattern Matching

Ebling, J.
Scheuermann, G.

Integrated Visualization of Morphologic and Perfusion Data for the Analysis of Coronary Artery Disease

Oeltze, S.
Kuß, A.
Grothues, F.
Hennemuth, A.
Preim, B.

Structure-accentuating Dense Flow Visualization

Park, Sung W.
Yu, Hongfeng
Hotz, Ingrid
Kreylos, Oliver
Linsen, Lars
Hamann, Bernd

Simultaneous Classification of Time-Varying Volume Data Based on the Time Histogram

Akiba, Hiroshi
Fout, Nathaniel
Ma, Kwan-Liu

Affiliation Dynamics with an Application to Movie-Actor Biographies

Brandes, Ulrik
Hoefer, Martin
Pich, Christian

CVSgrab: Mining the History of Large Software Projects

Voinea, S. L.
Telea, A.

A Spectral Visualization System for Analyzing Financial Time Series Data

Keim, Daniel A.
Nietzschmann, Tilo
Schelwies, Norman
Schneidewind, Jörn
Schreck, Tobias
Ziegler, Hartmut

D2VR: High-Quality Volume Rendering of Projection-based Volumetric Data

Rautek, Peter
Csébfalvi, Balázs
Grimm, Sören
Bruckner, Stefan
Gröller, Eduard

PointCloudXplore: Visual Analysis of 3D Gene Expression Data Using Physical Views and Parallel Coordinates

Rübel, O.
Weber, G.H.
Sudar, D.
Malik, J.
Knowles, D.W.
Hamann, B.
Keränen, S.V.E.
Fowlkes, C.C.
Hendriks, C.L. Luengo
Simirenko, L.
Shah, N.Y.
Eisen, M.B.
Biggin, M.D.
Hagen, H.

The alpha -histogram: Using Spatial Coherence to Enhance Histograms and Transfer Function Design

Lundström, Claes
Ynnerman, Anders
Ljung, Patric
Persson, Anders
Knutsson, Hans

Integrating Dynamic Deformations into Interactive Volume Visualization

Brunet, Tom
Nowak, K. Evan
Gleicher, Michael

Lossless Geometry Compression for Steady-State and Time-Varying Irregular Grids

Chen, Dan
Chiang, Yi-Jen
Memon, Nasir
Wu, Xiaolin

A Granular Three Dimensional Multiresolution Transform

Entezari, Alireza
Meng, Tai
Bergner, Steven
Möller, Torsten

Automating Transfer Function Design for Volume Rendering Using Hierarchical Clustering of Material Boundaries

ereda, Petr
Vilanova, Anna
Gerritsen, Frans A.

Fast Ray Traversal of Tetrahedral and Hexahedral Meshes for Direct Volume Rendering

Marmitt, Gerd
Slusallek, Philipp

Multiresolution Interblock Interpolation in Direct Volume Rendering

Ljung, Patric
Lundström, Claes
Ynnerman, Anders

Improving the Quality of Multi-resolution Volume Rendering

Younesy, H.
Möller, T.
Carr, H.

An Interactive Visualization System for Quantifying Coral Structures

Kruszynski, K. J.
Liere, R. van
Kaandorp, J. A.

Data Reconstruction and Visualization Techniques for Forensic Pathology

Ehlert, Alexander
Salah, Zein
Bartz, Dirk

Perspective Isosurface and Direct Volume Rendering for Virtual Endoscopy Applications

Scharsach, Henning
Hadwiger, Markus
Neubauer, André
Wolfsberger, Stefan
Bühler, Katja

A Case Study: Visualizing Material Point Method Data

Bigler, James
Guilkey, James
Gribble, Christiaan
Hansen, Charles
Parker, Steven G.

Visualizing the Phonon Map

Deines, E.
Michel, F.
Bertram, M.
Hagen, H.
Nielson, G. M.

Enhanced Visualizations of Thermographic Data in Process Industry

Seipel, S.
Forsberg, A.- K.
Wesslén, D.

Application-Oriented Extensions of Profile Flags

Mlejnek, Matej
Ermes, Pierre
Vilanova, Anna
Rijt, Rob van der
Bosch, Harrie van den
Gerritsen, Frans
Gröller, M. Eduard

3D Soft Segmentation and Visualization of Medical Data Based on Nonlinear Diffusion and Distance Functions

Petersch, B.
Serrano-Serrano, O.
Hönigmann, D.

Real-Time Super Resolution Contextual Close-up of Clinical Volumetric Data

Taerum, T.
Sousa, M. C.
Samavati, F.
Chan, S.
Mitchell, J. R.


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Recent Submissions

Now showing 1 - 43 of 43
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    GPU-Accelerated Volume Splatting With Elliptical RBFs
    (The Eurographics Association, 2006) Neophytou, Neophytos; Mueller, Klaus; McDonnell, Kevin T.; Hong, Wei; Guan, Xin; Qin, Hong; Kaufman, Arie; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Radial Basis Functions (RBFs) have become a popular rendering primitive, both in surface and in volume rendering. This paper focuses on volume visualization, giving rise to 3D kernels. RBFs are especially convenient for the representation of scattered and irregularly distributed point samples, where the RBF kernel is used as a blending function for the space in between samples. Common representations employ radially symmetric RBFs, and various techniques have been introduced to render these, also with efficient implementations on programmable graphics hardware (GPUs). In this paper, we extend the existing work to more generalized, ellipsoidal RBF kernels, for the rendering of scattered volume data. We devise a post-shaded kernel-centric rendering approach, specifically designed to run efficiently on GPUs, and we demonstrate our renderer using datasets from subdivision volumes and computational science.
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    Hardware-accelerated Extraction and Rendering of Point Set Surfaces
    (The Eurographics Association, 2006) Tejada, E.; Gois, J. P.; Nonato, L. G.; Castelo, A.; Ertl, T.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Point-based models are gaining lately considerable attention as an alternative to traditional surface meshes. In this context, Point Set Surfaces (PSS) were proposed as a modeling and rendering method with important topological and approximation properties. However, ray-tracing PSS is computationally expensive. Therefore, we propose an interactive ray-tracing algorithm for PSS implemented completely on commodity graphics hardware. We also exploit the advantages of PSS to propose a novel technique for extracting surfaces directly from volumetric data. This technique is based on the well known predictor-corrector principle from the numerical methods for solving ordinary differential equations. Our technique provides good approximations to surfaces defined by a certain property in the volume, such as iso-surfaces or surfaces located at regions of high gradient magnitude. Also, local details of the surfaces could be manipulated by changing the local polynomial approximation and the smoothing parameters used. Furthermore, the surfaces generated are smooth and low frequency noise is naturally handled.
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    GPU-Based Hyperstreamlines for Diffusion Tensor Imaging
    (The Eurographics Association, 2006) Reina, G.; Bidmon, K.; Enders, F.; Hastreiter, P.; Ertl, T.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    We propose a new approach for the visualization of hyperstreamlines, which offers potential for better scalability than the conventional polygon-based approach. Our method circumvents the bandwidth bottleneck between the CPU and GPU by transmitting a small set of parameters for each tube segment and generates the surface directly on the GPU using the classical sphere tracing approach. This reduces the load on the CPU that would otherwise need to provide a suitable level-of-detail representation of the scene, while offering even higher quality in the resulting surfaces since every fragment is traced individually. We demonstrate the effectiveness of this approach by comparing it to the performance and output of conventional visualization tools in the application area of diffusion tensor imaging of human brain MR scans. The method presented here can also be utilized to generate other types of surfaces on the GPU that are too complex to handle with direct ray casting and can therefore be adapted for other applications.
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    GPUFLIC: Interactive and Accurate Dense Visualization of Unsteady Flows
    (The Eurographics Association, 2006) Li, Guo-Shi; Tricoche, Xavier; Hansen, Charles; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    The paper presents an efficient and accurate implementation of Unsteady Flow LIC (UFLIC) on the Graphics Processing Unit (GPU). We obtain the same, high quality texture representation of unsteady two-dimensional flows as the original, time-consuming method but leverage the features of today s commodity hardware to achieve interactive frame rates. Despite a remarkable number of recent contributions in the field of texture-based visualization of time-dependent vector fields, the present paper is the first to provide a faithful implementation of that prominent technique fully supported by the graphics pipeline.
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    Combining Extended Table Lens and Treemap Techniques for Visualizing Tabular Data
    (The Eurographics Association, 2006) Telea, Alexandru; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    We present a framework for visualizing large tabular data that combines two views: the table view and the treemap view. The table view extends the known table lens as follows: We cluster related elements to reduce subsampling artifacts and achieve table size independent rendering time; we use multiple-column sorting to create scenariospecific data hierarchies on the fly; and we use shaded cushions to show data structure and variation. Hierarchies built in the table view are shown in a customizable treemap view. One can choose both layout and rendering by a few clicks, effectively creating visual scenarios on-the-fly. We illustrate our framework on real-life stock data.
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    Natural Visualizations
    (The Eurographics Association, 2006) Haroz, Steve; Ma, Kwan-Liu; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    This paper demonstrates the prevalence of a shared characteristic between visualizations and images of nature. We have analyzed visualization competitions and user studies of visualizations and found that the more preferred, better performing visualizations exhibit more natural characteristics. Due to our brain being wired to perceive natural images [SO01], testing a visualization for properties similar to those of natural images can help show how well our brain is capable of absorbing the data. In turn, a metric that finds a visualization s similarity to a natural image may help determine the effectiveness of that visualization. We have found that the results of comparing the sizes and distribution of the objects in a visualization with those of natural standards strongly correlate to one s preference of that visualization.
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    Evaluating the Effectiveness of Tree Visualization Systems for Knowledge Discovery
    (The Eurographics Association, 2006) Wang, Yue; Teoh, Soon Tee; Ma, Kwan-Liu; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    User studies, evaluations, and comparisons of tree visualization systems have so far focused on questions that can readily be answered by simple, automated queries without needing visualization. Studies are lacking on the actual use of tree visualization in discovering intrinsic, hidden, non-trivial and potentially valuable knowledge. We have thus formulated a set of tree exploration tasks not previously considered and have performed user studies and analysis to determine how visualization helps users to perform these tasks. In our study, we evaluated three systems: RINGS (a node-link representation), Treemap (a containment representation), and Windows Explorer. Our findings suggest a few ways that tree visualization helps users to perceive different aspects of hierarchical structured information. We then explain how these visual representations are able to trigger human perception to make these discoveries.
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    PhylloTrees: Phyllotactic Patterns for Tree Layout
    (The Eurographics Association, 2006) Neumann, Petra; Carpendale, Sheelagh; Agarawala, Anand; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Motivations for drawing hierarchical structures are probably as diverse as datasets to visualize. This ubiquity of tree structures has lead to a manifold of tree layout algorithms and tree visualization systems. While many tree layouts exist, increasingly massive data sets, expanding computational power, and still relatively limited display space make tree layout algorithms a topic of ongoing interest. We explore the use of nature s phyllotactic patterns to inform the layout of hierarchical data. These naturally occurring patterns provide a non-overlapping, optimal packing when the total number of nodes is not known a priori. We present PhylloTrees, a family of expandable tree layouts based on these patterns.
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    Efficient Surface Reconstruction from Noisy Data using Regularized Membrane Potentials
    (The Eurographics Association, 2006) Jalba, A. C.; Roerdink, J. B. T. M.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    We present a novel, physically-motivated method for surface reconstruction that can recover smooth surfaces from noisy and sparse data sets, without using orientation information. A new volumetric technique based on regularized-membrane potentials for aggregating the input sample points is introduced, which manages improved noise tolerability and outlier removal, without sacrificing much with respect to detail (feature) recovery. In this method, sample points are first aggregated on a volumetric grid. A labeling algorithm that relies on intrinsic properties of the smooth scalar field emerging after aggregation is used to classify grid points as exterior or interior to the surface. We also introduce a mesh-smoothing paradigm based on a mass-spring system, enhanced with a bending-energy minimizing term to ensure that the final triangulated surface is smoother than piecewise linear. The method compares favorably with respect to previous approaches in terms of speed and flexibility.
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    Robust Surface Detection for Variance Comparison and Dimensional Measurement
    (The Eurographics Association, 2006) Heinzl, C.; Klingesberger, R.; Kastner, J.; Gröller, E.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    This paper describes a robust method for creating surface models from volume datasets with distorted density values due to artefacts and noise. Application scenario for the presented work is variance comparison and dimensional measurement of homogeneous industrial components in industrial high resolution 3D computed tomography (3D-CT). We propose a pipeline which uses common 3D image processing filters for pre-processing and segmentation of 3D-CT datasets in order to create the surface model. In particular, a pre-filtering step reduces noise and artefacts without blurring edges in the dataset. A watershed filter is applied on the gradient information of the smoothed data to create a binary dataset. Finally the surface model is constructed, using constrained elastic-surface nets to generate a smooth but feature preserving mesh of a binary volume. The major contribution of this paper is the development of the specific processing pipeline for homogeneous industrial components to handle large resolution data of industrial CT scanners. The pipeline is crucial for the following visual inspection of deviations.
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    Direct Isosurface Extraction from Scattered Volume Data
    (The Eurographics Association, 2006) Rosenthal, Paul; Linsen, Lars; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Isosurface extraction is a standard visualization method for scalar volume data and has been subject to research for decades. Nevertheless, to our knowledge, no isosurface extraction method exists that directly extracts surfaces from scattered volume data without 3D mesh generation or reconstruction over a structured grid. We propose a method based on spatial domain partitioning using a kd-tree and an indexing scheme for efficient neighbor search. Our approach consists of a geometry extraction and a rendering step. The geometry extraction step computes points on the isosurface by linearly interpolating between neighboring pairs of samples. The neighbor information is retrieved by partitioning the 3D domain into cells using a kd-tree. The cells are merely described by their index and bitwise index operations allow for a fast determination of potential neighbors. We use an angle criterion to select appropriate neighbors from the small set of candidates. The output of the geometry step is a point cloud representation of the isosurface. The final rendering step uses point-based rendering techniques to visualize the point cloud. Our direct isosurface extraction algorithm for scattered volume data produces results of quality close to the results from standard isosurface extraction algorithms for gridded volume data (like marching cubes). In comparison to 3D mesh generation algorithms (like Delaunay tetrahedrization), our algorithm is about one order of magnitude faster for the examples used in this paper.
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    Knowledge-Based Out-of-Core Algorithms for Data Management in Visualization
    (The Eurographics Association, 2006) Chisnall, David; Chen, Min; Hansen, Charles; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Data management is the very first issue in handling very large datasets. Many existing out-of-core algorithms used in visualization are closely coupled with application-specific logic. This paper presents two knowledgebased out-of-core prefetching algorithms that do not use hard-coded rendering-related logic. They acquire the knowledge of the access history and patterns dynamically, and adapt their prefetching strategies accordingly. We have compared the algorithms with a demand-based algorithm, as well as a more domain-specific out-of-core algorithm. We carried out our evaluation in conjunction with an example application where rendering multiple point sets in a volume scene graph put a great strain on the rendering algorithm in terms of memory management. Our results have shown that the knowledge-based approach offers a better cache-hit to disk-access trade-off. This work demonstrates that it is possible to build an out-of-core prefetching algorithm without depending on rendering-related application-specific logic. The knowledge based approach has the advantage of being generic, efficient, flexible and self-adaptive.
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    Terrain Rendering using Spherical Clipmaps
    (The Eurographics Association, 2006) Clasen, Malte; Hege, Hans-Christian; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    We describe a terrain rendering algorithm for spherical terrains based on clipmaps. It leverages the high geometry throughput of current GPU to render large static triangle sets. The vertices are displaced by a height map texture. Our main contribution is mapping of texture coordinates to calculate the height map sample position based on the static vertex offset and the variable view position.
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    Volume Composition Using Eye Tracking Data
    (The Eurographics Association, 2006) Lu, Aidong; Maciejewski, Ross; Ebert, David S.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    This paper presents a method to automate rendering parameter selection, simplifying tedious user interaction and improving the usability of visualization systems. Our approach acquires regions-of-interest for a dataset with an eye tracker and simple user interaction. Based on this importance information, we then automatically compute reasonable rendering parameters using a set of heuristic rules adapted from visualization experience and psychophysics experiments. While the parameter selections for a specific visualization task are subjective, our approach provides good starting results that can be refined by the user. Our system improves the interactivity of a visualization system by significantly reducing the necessary parameter selection and providing good initial rendering parameters for newly acquired datasets of similar types.
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    Path Line Oriented Topology for Periodic 2D Time-Dependent Vector Fields
    (The Eurographics Association, 2006) Shi, K.; Theisel, H.; Weinkauf, T.; Hauser, H.; Hege, H.-C.; Seidel, H.-P.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    This paper presents an approach to extracting a path line oriented topological segmentation for periodic 2D timedependent vector fields. Topological methods aiming in capturing the asymptotic behavior of path lines rarely exist because path lines are usually only defined over a fixed time-interval, making statements about their asymptotic behavior impossible. For the data class of periodic vector fields, this restriction does not apply any more. Our approach detects critical path lines as well as basins from which the path lines converge to the critical ones. We demonstrate our approach on a number of test data sets.
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    Texture Advection on Stream Surfaces: A Novel Hybrid Visualization Applied to CFD Simulation Results
    (The Eurographics Association, 2006) Laramee, Robert S.; Garth, Christoph; Schneider, Jürgen; Hauser, Helwig; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Stream surfaces are a classic flow visualization technique used to portray the characteristics of vector fields, and texture advection research has made rapid advances in recent years. We present a novel hybrid visualization of texture advection on stream surfaces. This approach conveys properties of the vector field that stream surfaces alone cannot. We apply the visualization technique to various patterns of flow from CFD data important to automotive engine simulation including two patterns of in-cylinder flow (swirl and tumble motion) as well as flow through a cooling jacket. In addition, we explore multiple vector fields defined at the stream surface such as velocity, vorticity, and pressure gradient. The results of our investigation highlight both the strengths and limitations of the hybrid stream surface-texture advection visualization technique and offer new insight to engineers exploring and analyzing their simulations.
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    Enhancing Slice-based Visualizations of Medical Volume Data
    (The Eurographics Association, 2006) Tietjen, Christian; Meyer, Björn; Schlechtweg, Stefan; Preim, Bernhard; Hertel, Ilka; Strauß, Gero; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Slice-based visualizations of CT and MRI data are frequently used for diagnosis, intervention planning and intraoperative navigation since they allow a precise analysis and localization. We present new techniques to enhance the visualization of cross sectional medical image data. Our work is focussed on intervention planning and intraoperative navigation. We address the following problems of slice-based visualization in these areas: the lack of a graphical overview on the positions of anatomic structures, the localization of a target structure and the display of safety zones around pathologic structures. To improve the overview, we introduce LIFTCHARTs, attached as vertical bars to a slice-based visualization. For localizing target structures, we introduce halos. These techniques restrict the occlusion of the original data to a minimum and avoid any modification of the original data. To demonstrate the usability of these visualization techniques, we show two application scenarios in which the techniques come into operation.
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    Segmentation of Flow Fields using Pattern Matching
    (The Eurographics Association, 2006) Ebling, J.; Scheuermann, G.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Due to the amount of data nowadays, automatic detection, classification and visualization of features is necessary for a thorough inspection of flow data sets. Pattern matching using vector valued templates has already been applied successfully for the detection of features. In this paper, the approach is extended to automatically compute feature based segmentations of flow data sets. Different problems of the segmentation like the influence of thresholds, overlapping features, and classification errors are discussed. Visualizations of the segmentation display important structures of the flow and highlight the interesting features. The segmentation algorithm presented in this paper is applicable to 2D and 3D vector fields as well as to time-dependent data.
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    Integrated Visualization of Morphologic and Perfusion Data for the Analysis of Coronary Artery Disease
    (The Eurographics Association, 2006) Oeltze, S.; Kuß, A.; Grothues, F.; Hennemuth, A.; Preim, B.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    We present static and dynamic techniques to visualize perfusion data and to relate perfusion data to morphologic image data. In particular, we describe the integrated analysis of MRI myocardial perfusion data with CT coronary angiographies depicting the morphology. We refined the Bull s-Eye Plot, a wide-spread and accepted analysis tool in cardiac diagnosis, to show aggregated information of perfusion data at rest and under stress. The correlation between regions of the myocard with reduced perfusion and 3d renditions of the coronary vessels can be explored within a synchronized visualization of both. With our research, we attempt to improve the diagnosis of early stage coronary artery disease.
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    Structure-accentuating Dense Flow Visualization
    (The Eurographics Association, 2006) Park, Sung W.; Yu, Hongfeng; Hotz, Ingrid; Kreylos, Oliver; Linsen, Lars; Hamann, Bernd; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Vector field visualization approaches can broadly be categorized into approaches that directly visualize local or integrated flow and approaches that analyze the topological structure and visualize extracted features. Our goal was to come up with a method that falls into the first category, yet reveals structural information. We have developed a dense flow visualization method that shows the overall flow behavior while accentuating structural information without performing a topological analysis. Our method is based on a geometry-based flow integration step and a texture-based visual exploration step. The flow integration step generates a density field, which is written into a texture. The density field is generated by tracing particles under the influence of the underlying vector field. When using a quasi-random seeding strategy for initialization, the resulting density is high in attracting regions and low in repelling regions. Density is measured by the number of particles per region accumulated over time. We generate one density field using forward and one using backward propagation. The density fields are explored using texture-based rendering techniques. We generate the two output images separately and blend the results, which allows us to distinguish between inflow and outflow regions. We obtained dense flow visualizations that display the overall flow behavior, emphasize critical and separating regions, and indicate flow direction in the neighborhood of these regions. We have test our method for isolated first-order singularities and real data sets.
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    Simultaneous Classification of Time-Varying Volume Data Based on the Time Histogram
    (The Eurographics Association, 2006) Akiba, Hiroshi; Fout, Nathaniel; Ma, Kwan-Liu; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    An important challenge in the application of direct volume rendering to time-varying data is the specification of transfer functions for all time steps. Very little research has been devoted to this problem, however. To address this issue we propose an approach which allows simultaneous classification of the entire time series. We explore options for transfer function specification that are based, either directly or indirectly, on the time histogram. Furthermore, we consider how to effectively provide feedback for interactive classification by exploring options for simultaneous rendering of the time series, again based on the time histogram. Finally, we apply this approach to several large time-varying data sets where we show that the important features at all times are captured with about the same effort it takes to classify one time step using conventional classification.
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    Affiliation Dynamics with an Application to Movie-Actor Biographies
    (The Eurographics Association, 2006) Brandes, Ulrik; Hoefer, Martin; Pich, Christian; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    We propose a visualization approach for dynamic affiliation networks in which events are characterized by a set of descriptors. It uses a radial ripple metaphor to display the passing of time and conveys relations among the different constituents through appropriate layout. Our method is particularly suitable when assuming an egocentric perspective, and we illustrate it on movie-actor biographies.
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    CVSgrab: Mining the History of Large Software Projects
    (The Eurographics Association, 2006) Voinea, S. L.; Telea, A.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Many software projects use Software Configuration Management systems to support their development process. Such systems accumulate in time large amounts of information useful for process accounting and auditing. We study how software developers can get insight in this information in order to understand the project context and the product artifacts. To this end, we propose several new techniques for visual mining of project evolution. Central to our approach is a file-based evolution visualization, where each project is shown as a set of horizontal stripes depicting files along the time axis. We propose several mechanisms for interactively building layouts in this display, and for correlating the evolution with the results of various software metrics. We demonstrate the usefulness of our approach on real- life data sets.
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    A Spectral Visualization System for Analyzing Financial Time Series Data
    (The Eurographics Association, 2006) Keim, Daniel A.; Nietzschmann, Tilo; Schelwies, Norman; Schneidewind, Jörn; Schreck, Tobias; Ziegler, Hartmut; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Visual data analysis of time related data sets has attracted much research interest recently, and a number of sophisticated visualization methods have been proposed in the past. In financial analysis, however, the most important and most common visualization techniques for time series data is the traditional line- or bar chart. Although these are intuitive and make it easy to spot the effect of key events on a asset s price, and its return over a given period of time, price charts do not allow the easy perception of relative movements in terms of growth rates, which is the key feature of any price-related time series. This paper presents a novel Growth Matrix visualization technique for analyzing assets. It extends the ability of existing chart techniques by not only visualizing asset return rates over fixed time frames, but over the full spectrum of all subintervals present in a given time frame, in a single view. At the same time, the technique allows a comparison of subinterval return rates among groups of even a few hundreds of assets. This provides a powerful way for analyzing financial data, since it allows the identification of strong and weak periods of assets as compared to global market characteristics, and thus allows a more encompassing visual classification into "good" and "poor" performers than existing chart techniques. We illustrate the technique by real-world examples showing the abilities of the new approach, and its high relevance for financial analysis tasks.
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    D2VR: High-Quality Volume Rendering of Projection-based Volumetric Data
    (The Eurographics Association, 2006) Rautek, Peter; Csébfalvi, Balázs; Grimm, Sören; Bruckner, Stefan; Gröller, Eduard; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Volume rendering techniques are conventionally classified as either direct or indirect methods. Indirect methods require to transform the initial volumetric model into an intermediate geometrical model in order to efficiently visualize it. In contrast, direct volume rendering (DVR) methods can directly process the volumetric data. Modern CT scanners usually provide data as a set of samples on a rectilinear grid, which is computed from the measured projections by discrete tomographic reconstruction. Therefore the rectilinear grid can already be considered as an intermediate volume representation. In this paper we introduce direct direct volume rendering (D2VR). D2VR does not require a rectilinear grid, since it is based on an immediate processing of the measured projections. Arbitrary samples for ray casting are reconstructed from the projections by using the Filtered Back-Projection algorithm. Our method removes a lossy resampling step from the classical volume rendering pipeline. It provides much higher accuracy than traditional grid-based resampling techniques do. Furthermore we also present a novel high-quality gradient estimation scheme, which is also based on the Filtered Back-Projection algorithm.
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    PointCloudXplore: Visual Analysis of 3D Gene Expression Data Using Physical Views and Parallel Coordinates
    (The Eurographics Association, 2006) Rübel, O.; Weber, G.H.; Keränen, S.V.E.; Fowlkes, C.C.; Hendriks, C.L. Luengo; Simirenko, L.; Shah, N.Y.; Eisen, M.B.; Biggin, M.D.; Hagen, H.; Sudar, D.; Malik, J.; Knowles, D.W.; Hamann, B.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    To allow a more rigorous understanding of animal gene regulatory networks, the Berkeley Drosophila Transcription Network Project (BDTNP) has developed a suite of methods that support quantitative, computational analysis of three-dimensional (3D) gene expression patterns with cellular resolution in early Drosophila embryos. Here we report the first components of a visualization tool, PointCloudXplore, that allows the relationships between different gene s expression to be analyzed using the BDTNP s datasets. PointCloudXplore uses the established visualization techniques of multiple views, brushing, and linking to support the analysis of high-dimensional datasets that describe many genes expression. Each of the views in PointCloud- Xplore shows a different gene expression data property. Brushing is used to select and emphasize data associated with defined subsets of embryo cells within a view. Linking is used to show in additional views the expression data for a group of cells that have first been highlighted as a brush in a single view, allowing further data subset properties to be determined. In PointCloudXplore, physical views of the data are linked to parallel coordinates. Physical views show the spatial relationships between different genes expression patterns within the embryo. Parallel coordinates, on the other hand, show only some features of each gene s expression, but allow simultaneous analysis of data for many more genes than would be possible in a physical view. We have developed several extensions to standard parallel coordinates to facilitate brushing the visualization of 3D gene expression data.
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    The alpha -histogram: Using Spatial Coherence to Enhance Histograms and Transfer Function Design
    (The Eurographics Association, 2006) Lundström, Claes; Ynnerman, Anders; Ljung, Patric; Persson, Anders; Knutsson, Hans; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    The high complexity of Transfer Function (TF) design is a major obstacle to widespread routine use of Direct Volume Rendering, particularly in the case of medical imaging. Both manual and automatic TF design schemes would benefit greatly from a fast and simple method for detection of tissue value ranges. To this end, we introduce the a-histogram, an enhancement that amplifies ranges corresponding to spatially coherent materials. The properties of the a-histogram have been explored for synthetic data sets and then successfully used to detect vessels in 20 Magnetic Resonance angiographies, proving the potential of this approach as a fast and simple technique for histogram enhancement in general and for TF construction in particular.
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    Integrating Dynamic Deformations into Interactive Volume Visualization
    (The Eurographics Association, 2006) Brunet, Tom; Nowak, K. Evan; Gleicher, Michael; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Non-linear geometric deformation (or warping) is a useful tool for working with volumes. Unfortunately, the computational expense of performing the resampling needed to implement volume deformation has precluded its use in interactive applications. In this paper, we show how non-linear deformations can be integrated into interactive volume visualization allowing for dynamic deformations to be used along with interactive viewing, exploration, and manipulation tools. We describe how hardware assisted volume rendering can be adapted to resample volume deformations, leveraging programmable shaders to compute deformations and the local coordinate transformations required for shading effects. We describe how volume interaction techniques, such as ray picking and plane slicing, can be used in concert with our deformation methods. Our methods extend to simultaneous display of multiple volumes enabling comparisons. We demonstrate dynamic volume deformation at interactive rates on commodity hardware for interactive deformation control, animated deformations, and volume widgets.
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    Lossless Geometry Compression for Steady-State and Time-Varying Irregular Grids
    (The Eurographics Association, 2006) Chen, Dan; Chiang, Yi-Jen; Memon, Nasir; Wu, Xiaolin; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    In this paper we investigate the problem of lossless geometry compression of irregular-grid volume data represented as a tetrahedral mesh. We propose a novel lossless compression technique that effectively predicts, models, and encodes geometry data for both steady-state (i.e., with only a single time step) and time-varying datasets. Our geometry coder is truly lossless and also does not need any connectivity information. Moreover, it can be easily integrated with a class of the best existing connectivity compression techniques for tetrahedral meshes with a small amount of overhead information. We present experimental results which show that our technique achieves superior compression ratios, with reasonable encoding times and fast (linear) decoding times.
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    A Granular Three Dimensional Multiresolution Transform
    (The Eurographics Association, 2006) Entezari, Alireza; Meng, Tai; Bergner, Steven; Möller, Torsten; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    We propose a three dimensional multi-resolution scheme to represent volumetric data in resolutions which are powers of two, resolving the rigidity of the commonly used separable Cartesian multi-resolution schemes in 3D that only allow for change of resolution by a power of eight. Through in-depth comparisons with the counterpart resampling solutions on the Cartesian lattice, we demonstrate the superiority of our subsampling scheme. We derive and document the Fourier domain analysis of this representation. Using such an analysis one can obtain ideal and discrete multidimensional filters for this multi-resolution scheme.
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    Automating Transfer Function Design for Volume Rendering Using Hierarchical Clustering of Material Boundaries
    (The Eurographics Association, 2006) ereda, Petr; Vilanova, Anna; Gerritsen, Frans A.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Transfer function design plays a crucial role in direct volume rendering. Furthermore, it has a major influence on the efficiency of the visualization process. We have developed a framework that facilitates the semi-automatic design of transfer functions. Similarly to other approaches we generate clusters in the transfer function domain. We created a real-time interaction with a hierarchy of clusters. This interaction effectively substitutes cumbersome settings of clustering thresholds. Our framework is also able to easily combine different clustering criteria. We have developed two similarity measures for clustering of material boundaries. One is based on the similarity of the boundaries in the transfer function domain and the other on their spatial relation. We use the LH space as the transfer function domain. This space facilitates the clustering of material boundaries. We demonstrate our approach on several examples.
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    Fast Ray Traversal of Tetrahedral and Hexahedral Meshes for Direct Volume Rendering
    (The Eurographics Association, 2006) Marmitt, Gerd; Slusallek, Philipp; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    The importance of high-performance rendering of unstructured or curvilinear data sets has increased significantly, mainly due to its use in scientific simulations such as computational fluid dynamics and finite element computations. However, the unstructured nature of these data sets lead to rather slow implementations for ray tracing. The approaches discussed in this paper are fast and scalable towards realtime ray tracing applications. We evaluate new algorithms for rendering tetrahedral and hexahedral meshes. In each algorithm, the first cell along a ray is found using common realtime ray tracing techniques. For traversing subsequent cells within the volume, Plücker coordinates as well as ray-bilinear patch intersection tests are used. Since the volume is rendered directly, all algorithms are applicable for isosurface rendering, maximum-intensity projection, and emissionabsorption models.
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    Multiresolution Interblock Interpolation in Direct Volume Rendering
    (The Eurographics Association, 2006) Ljung, Patric; Lundström, Claes; Ynnerman, Anders; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    We present a direct interblock interpolation technique that enables direct volume rendering of blocked, multiresolution volumes. The proposed method smoothly interpolates between blocks of arbitrary block-wise level-of-detail (LOD) without sample replication or padding. This permits extreme changes in resolution across block boundaries and removes the interblock dependency for the LOD creation process. In addition the full data reduction from the LOD selection can be maintained throughout the rendering pipeline. Our rendering pipeline employs a flat block subdivision followed by a transfer function based adaptive LOD scheme. We demonstrate the effectiveness of our method by rendering volumes of the order of gigabytes using consumer graphics cards on desktop PC systems.
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    Improving the Quality of Multi-resolution Volume Rendering
    (The Eurographics Association, 2006) Younesy, H.; Möller, T.; Carr, H.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    We propose a novel method to improve the quality of multi-resolution visualizations. We reduce aliasing artifacts by approximating the data distribution with a Gaussian basis function at each level of detail for more accurate rendering at coarser levels of detail. We then show an efficient implementation of our novel Gaussian based approximation scheme and show its superiority using numerical tests and compelling renderings.
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    An Interactive Visualization System for Quantifying Coral Structures
    (The Eurographics Association, 2006) Kruszynski, K. J.; Liere, R. van; Kaandorp, J. A.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Determining the shape of coral structures is an essential step for coral biologists to classify and compare corals. Currently, coral biologists analyze shape by performing manual measurements on photographs of coral colonies. In this paper we describe an interactive visualization system for measuring coral shapes in a robust and quantitative way. The input of the system is a CT scan of the coral, and the output consists of statistical distributions of various morphological properties. The approach is to first extract a skeleton from the CT scan, and then to perform measurements on the skeleton graph. Interactive visualization is necessary, since various features of the coral prevent the system from being fully automatic.
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    Data Reconstruction and Visualization Techniques for Forensic Pathology
    (The Eurographics Association, 2006) Ehlert, Alexander; Salah, Zein; Bartz, Dirk; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Forensic pathology is largely concerned with the determination of the cause and manner of deaths after accidents, or other circumstances in criminal investigations. A major task in that process is the documentation of surface injuries, which is traditionally done by drawing sketches, photography, or more recently by photogrammetry to generate a three-dimensional digital lesion cartography of the body surface. In this paper, we describe a semi-automatic processing pipeline how data from 3D photogrammetry is combined and used to generate a visual surface representation of accident victims. In that course, a number of steps are performed to provide a high-quality interactive, point-based visualization of the acquired data, which can be used in a more routine way than previous forensic surface methods.
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    Perspective Isosurface and Direct Volume Rendering for Virtual Endoscopy Applications
    (The Eurographics Association, 2006) Scharsach, Henning; Hadwiger, Markus; Neubauer, André; Wolfsberger, Stefan; Bühler, Katja; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Virtual endoscopy has proven to be a very powerful tool in endoscopic surgery. However, most virtual endoscopy systems are restricted to rendering isosurfaces or require segmentation in order to visualize additional objects behind occluding tissue. This paper presents a system for real-time perspective direct volume and isosurface rendering, which allows to simultaneously visualize both the interesting tissue and everything that is behind. Large volume data can be viewed seamlessly from inside or outside the volume without any pre-computation or segmentation. Our system uses a novel ray-casting pipeline for GPUs that has been optimized for the requirements of virtual endoscopy and also allows easy incorporation of auxiliary geometry, e.g., for displaying parts of the endoscopic device, pointers, or grid lines for orientation purposes. We present three main applications of this system and the underlying ray-casting algorithm. Although our ray-casting approach is of general applicability, we have specifically applied it to virtual colonoscopy, virtual angioscopy, and virtual pituitary surgery.
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    A Case Study: Visualizing Material Point Method Data
    (The Eurographics Association, 2006) Bigler, James; Guilkey, James; Gribble, Christiaan; Hansen, Charles; Parker, Steven G.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    The Material Point Method is used for complex simulation of solid materials represented using many individual particles. Visualizing such data using existing polygonal or volumetric methods does not accurately encapsulate both the particle and macroscopic properties of the data. In this case study we present various methods used to visualize the particle data as spheres and explain and evaluate two methods of augmenting the visualization using silhouette edges and advanced illumination such as ambient occlusion.We also present informal feedback received from the application scientists who use these methods in their workflow.
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    Visualizing the Phonon Map
    (The Eurographics Association, 2006) Deines, E.; Michel, F.; Bertram, M.; Hagen, H.; Nielson, G. M.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    In this work we present several visualization approaches for analyzing acoustic behavior inside a room. Our methods are based on the results of the phonon tracing algorithm. For a simulated phonon map we examine the influence of the room surfaces on the wave fronts during their propagation from the sound source. Our visualization is based on individual phonon and surface representations as well as scattered data interpolation. Additionally, an observation of acoustic behavior at different positions inside the room using colored and deformed spheres is possible.
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    Enhanced Visualizations of Thermographic Data in Process Industry
    (The Eurographics Association, 2006) Seipel, S.; Forsberg, A.- K.; Wesslén, D.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    In this paper, we describe an improved method for visualization of thermographic data in the paper and pulp process industry. We present an application that allows process operators to freely choose how absolute temperatures and time varying changes of thermographic scans should be mapped to colors and/or 3D shapes. Of the possible combinations, we selected two different forms of 3D visualizations and an existing conventional 2D map visualization. We then evaluated these visualization forms with regard to their effectiveness in experimental field studies. The field tests were carried out to measure the operators performance in early detection of insulation damages on lime kilns. The results we obtained from the study show that the two new forms of 3D visualization lead to a reduction of the detection times by about two-thirds and one-third, respectively, when compared to the conventional 2D map representation. Since lime kiln monitoring is based on the rather generic method of continuous thermographic imaging, we suggest that these results also hold for the control and surveillance of other processes.
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    Application-Oriented Extensions of Profile Flags
    (The Eurographics Association, 2006) Mlejnek, Matej; Ermes, Pierre; Vilanova, Anna; Rijt, Rob van der; Bosch, Harrie van den; Gerritsen, Frans; Gröller, M. Eduard; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    This paper discusses two applications of probing dense volumetric data for MR orthopedics and dynamic contrast enhanced MRI mammography. In order not to reduce the context information and to extract the essential part of the data, we apply Profile Flags. A Profile Flag is a 3D glyph for probing and annotating the volumetric data. The first application area deals with visualization of T2 profiles for interactive inspection of knee cartilage and detection of lesions. In the second application, we present the usability the Profile Flags for measuring of time-signal profiles for a set of time-dependent MR volumes. Several extensions of the basic Profile Flag concept are described in detail and discussed. These extensions include selection of a set of profiles based on spatial as well as curve differences, automatic positioning of the Profile Flags, and adaptation for probing of time-varying volumetric data. Additionally, we include the evaluation of the used methods by our medical partners.
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    3D Soft Segmentation and Visualization of Medical Data Based on Nonlinear Diffusion and Distance Functions
    (The Eurographics Association, 2006) Petersch, B.; Serrano-Serrano, O.; Hönigmann, D.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    Visualization of medical 3D data is a complex problem, since the raw data is often unsuitable for standard techniques like Direct Volume Rendering. Some kind of pre-treatment is necessary, usually segmentation of the structures of interest, which in turn is a difficult task. Most segmentation techniques yield a model without indicating any uncertainty. Visualization then can be misleading, especially if the original data is of poor contrast. We address this dilemma proposing a geometric approach based on distance on image manifolds and an alternative approach based on nonlinear diffusion. An effective algorithm solving Hamilton-Jacobi equations allows for computing a distance function for 2D and 3D manifolds at interactive rates. An efficient implementation of a semi-implicit operator splitting scheme accomplishes interactivity for the diffusion-based strategy. We establish a model which incorporates local information about its reliability and can be visualized with standard techniques. When interpreting the result of the segmentation in a diagnostic setting, this information is of utmost importance.
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    Real-Time Super Resolution Contextual Close-up of Clinical Volumetric Data
    (The Eurographics Association, 2006) Taerum, T.; Sousa, M. C.; Samavati, F.; Chan, S.; Mitchell, J. R.; Beatriz Sousa Santos and Thomas Ertl and Ken Joy
    We present an illustrative visualization system for real-time and high quality rendering of clinical volumetric medical data. Our technique is inspired by a medical illustration technique for depicting contextual close-up views of selected regions of interest where internal anatomical features are rendered in high detail. Our method integrates four important components: decimation of original volume for interactivity, B-spline subdivision for super-resolution rendering, fast gradient quantization technique for feature extraction and GPU fragment shaders for gradient dependent rendering and transfer functions. Examples with clinical CT and MRI data demonstrate the capabilities of our system.