EuroVis06: Joint Eurographics - IEEE VGTC Symposium on Visualization

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

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