EuroVis06: Joint Eurographics - IEEE VGTC Symposium on Visualization

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https://diglib.eg.org/handle/10.2312/399

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