bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enclosing Surfaces for Point Clusters Using 3D Discrete Voronoi Diagrams
Authors: Rosenthal Paul , Linsen Lars 
Published: July 2009

AbstractPoint clusters occur in both spatial and non‐spatial data. In the former context they may represent segmented particle data, in the latter context they may represent clusters in scatterplots. In order to visualize such point clusters, enclosing surfaces lead to much better comprehension than pure point renderings.We propose a flexible system for the generation of enclosing surfaces for 3D point clusters. We developed a GPU‐based 3D discrete Voronoi diagram computation that supports all surface extractions. Our system provides three different types of enclosing surfaces. By generating a discrete distance field to the point cluster and extracting an isosurface from the field, an enclosing surface with any distance to the point cluster can be generated. As a second type of enclosing surfaces, a hull of the point cluster is extracted. The generation of the hull uses a projection of the discrete Voronoi diagram of the point cluster to an isosurface to generate a polygonal surface. Generated hulls of non‐convex clusters are also non‐convex. The third type of enclosing surfaces can be created by computing a distance field to the hull and extracting an isosurface from the distance field. This method exhibits reduced bumpiness and can extract surfaces arbitrarily close to the point cluster without losing connectedness.We apply our methods to the visualization of multidimensional spatial and non‐spatial data. Multidimensional clusters are extracted and projected into a 3D visual space, where the point clusters are visualized. The respective clusters can also be visualized in object space when dealing with multidimensional particle data.
Force‐Directed Edge Bundling for Graph Visualization
Authors: Holten Danny , Van Wijk Jarke J. 
Published: July 2009

AbstractGraphs depicted as node‐link diagrams are widely used to show relationships between entities. However, node‐link diagrams comprised of a large number of nodes and edges often suffer from visual clutter. The use of edge bundling remedies this and reveals high‐level edge patterns. Previous methods require the graph to contain a hierarchy for this, or they construct a control mesh to guide the edge bundling process, which often results in bundles that show considerable variation in curvature along the overall bundle direction. We present a new edge bundling method that uses a self‐organizing approach to bundling in which edges are modeled as flexible springs that can attract each other. In contrast to previous methods, no hierarchy is used and no control mesh. The resulting bundled graphs show significant clutter reduction and clearly visible high‐level edge patterns. Curvature variation is furthermore minimized, resulting in smooth bundles that are easy to follow. Finally, we present a rendering technique that can be used to emphasize the bundling.
Visualizing the Evolution of Compound Digraphs with TimeArcTrees
Authors: Greilich Martin , Burch Michael , Diehl Stephan 
Published: July 2009

AbstractCompound digraphs are a widely used model in computer science. In many application domains these models evolve over time. Only few approaches to visualize such dynamic compound digraphs exist and mostly use animation to show the dynamics. In this paper we present a new visualization tool called TimeArcTrees that visualizes weighted, dynamic compound digraphs by drawing a sequence of node‐link diagrams in a single view. Compactness is achieved by aligning the nodes of a graph vertically. Edge crossings are reduced by drawing upward and downward edges separately as colored arcs. Horizontal alignment of the instances of the same node in different graphs facilitates comparison of the graphs in the sequence. Many interaction techniques allow to explore the given graphs. Smooth animation supports the user to better track the transitions between views and to preserve his or her mental map. We illustrate the usefulness of the tool by looking at the particular problem of how shortest paths evolve over time. To this end, we applied the system to an evolving graph representing the German Autobahn and its traffic jams.
SDViz: A Context‐Preserving Interactive Visualization System for Technical Diagrams
Authors: Woo Insoo , Kim Sung Ye , Maciejewski Ross , Ebert David S. , Ropp Timothy D. , Thomas Krystal 
Published: July 2009

AbstractWhen performing daily maintenance and repair tasks, technicians require access to a variety of technical diagrams. As technicians trace components and diagrams from page‐to‐page, within and across manuals, the contextual information of the components they are analyzing can easily be lost. To overcome these issues, we have developed a Schematic Diagram Visualization System (SDViz) designed for maintaining and highlighting contextual information in technical documents, such as schematic and wiring diagrams. Our system incorporates various features to aid in the navigation and diagnosis of faults, as well as maintaining contextual information when tracing components/connections through multiple diagrams. System features include highlighting relationships between components and connectors, diagram annotation tools, the animation of flow through the system, a novel contextual blending method, and a variety of traditional focus+context visualization techniques. We have evaluated the usefulness of our system through a qualitative user study in which subjects utilized our system in diagnosing faults during a standard aircraft maintenance exercise.
A Visualization Based Approach for Digital Signature Authentication
Authors: Xu Songhua , Yang Wenxia , Lau Francis C.M. 
Published: July 2009

AbstractWe propose a visualization based approach for digital signature authentication. Using our method, the speed and pressure aspects of a digital signature process can be clearly and intuitively conveyed to the user for digital signature authentication. Our design takes into account both the expressiveness and aesthetics of the derived visual patterns. With the visual aid provided by our method, digital signatures can be authenticated with better accuracy than using existing methods—even novices can examine the authenticity of a digital signature in most situations using our method. To validate the effectiveness of our method, we conducted a comprehensive user study which confirms positively the advantages of our approach. Our method can be employed as a new security enhancement measure for a range of business and legal applications in reality which involve digital signature authorization and authentication.
Extended Excentric Labeling
Authors: Bertini Enrico , Rigamonti Maurizio , Lalanne Denis 
Published: July 2009

AbstractThe paper presents an extension to the Excentric Labeling, a labeling technique to dynamically show labels around a movable lens. Each labels refers to one object within the lens and is connected to it through a line. The original implementation has several known limitations and potential improvements that we address in this work, like: high density areas, uneven density distributions, and summary statistics. We describe the implemented extensions and present a think‐aloud user study. The study shows that users can naturally understand and easily operate the majority of the implemented function but label scrolling, which requires additional research. From the study we also gained unanticipated requirements and interesting directions for further research.
Visual Analysis of Brain Activity from fMRI Data
Authors: Janoos Firdaus , Nouanesengsy Boonthanome , Machiraju Raghu , Shen Han Wei , Sammet Steffen , Knopp Michael , Mórocz István Á. 
Published: July 2009

AbstractClassically, analysis of the time‐varying data acquired during fMRI experiments is done using static activation maps obtained by testing voxels for the presence of significant activity using statistical methods. The models used in these analysis methods have a number of parameters, which profoundly impact the detection of active brain areas. Also, it is hard to study the temporal dependencies and cascading effects of brain activation from these static maps. In this paper, we propose a methodology to visually analyze the time dimension of brain function with a minimum amount of processing, allowing neurologists to verify the correctness of the analysis results, and develop a better understanding of temporal characteristics of the functional behaviour. The system allows studying time‐series data through specific volumes‐of‐interest in the brain‐cortex, the selection of which is guided by a hierarchical clustering algorithm performed in the wavelet domain. We also demonstrate the utility of this tool by presenting results on a real data‐set.
Map Displays for the Analysis of Scalar Data on Cerebral Aneurysm Surfaces
Authors: Neugebauer Mathias , Gasteiger Rocco , Beuing Oliver , Diehl Volker , Skalej Martin , Preim Bernhard 
Published: July 2009

AbstractCerebral aneurysms result from a congenital or evolved weakness of stabilizing parts of the vessel wall and potentially lead to rupture and a life‐threatening bleeding. Current medical research concentrates on the integration of blood flow simulation results for risk assessment of cerebral aneurysms. Scalar flow characteristics close to the aneurysm surface, such as wall shear stress, form an important part of the simulation results. Aneurysms exhibit variable surface shapes with only few landmarks. Therefore, the exploration and mental correlation of different surface regions is a difficult task. In this paper, we present an approach for the intuitive and interactive overview visualization of near wall flow data that is mapped onto the surface of a 3D model of a cerebral aneurysm. We combine a multi‐perspective 2D projection map with a standard 3D visualization and present techniques to facilitate the correlation between a 3D model and a related 2D map. An informal evaluation with 4 experienced radiologists has shown that the map‐based overview actually improves the surface exploration. Furthermore, different color schemes were discussed and, as a result, an appropriate color scheme for the visual analysis of the wall shear stress is presented.
Context‐aware Volume Modeling of Skeletal Muscles
Authors: Yan Zhicheng , Chen Wei , Lu Aidong , Ebert David S. 
Published: July 2009

AbstractThis paper presents an interactive volume modeling method that constructs skeletal muscles from an existing volumetric dataset. Our approach provides users with an intuitive modeling interface and produces compelling results that conform to the characteristic anatomy in the input volume. The algorithmic core of our method is an intuitive anatomy classification approach, suited to accommodate spatial constraints on the muscle volume. The presented work is useful in illustrative visualization, volumetric information fusion and volume illustration that involve muscle modeling, where the spatial context should be faithfully preserved.
Smooth Stream Surfaces of Fourth Order Precision
Authors: Schneider Dominic , Wiebel Alexander , Scheuermann Gerik 
Published: July 2009

AbstractWe introduce a novel technique for the construction of smooth stream surfaces of 4th order precision. While common stream surface techniques use linear interpolation for generating seed points for new streamlines in the refinement phase, we use Hermite interpolation. The derivatives needed for Hermite interpolation are obtained by integration along the streamlines. This yields stream surfaces of4th order precision. Additionally, we analyse the accuracy ofthe well known Hultquist approach and our new algorithm and proof that Hultquist's method is exact for linear vector fields. We compare both methods using the well known distance based and a novel error based refinement strategy. Our resulting surface is C1‐continuous, enabling improved rendering among other benefits.
Hierarchical Vortex Regions in Swirling Flow
Authors: Petz Christoph , Kasten Jens , Prohaska Steffen , Hege Hans‐Christian 
Published: July 2009

AbstractWe propose a new criterion to characterize hierarchical two‐dimensional vortex regions induced by swirling motion. Central to the definition are closed loops that intersect the flow field at a constant angle. The union of loops belonging to the same area of swirling motion defines a vortex region. These regions are disjunct but may be nested, thus introducing a spatial hierarchy of vortex regions. We present a parameter free algorithm for the identification of these regions. Since they are not restricted to star‐ or convex‐shaped geometries, we are able to identify also intricate regions, e.g., of elongated vortices. Computing an integrated value for each loop and mapping these values to a vortex region, introduces new ways for visualizing or filtering the vortex regions. Exemplary, an application based on the Rankine vortex model is presented. We apply our method to several CFD datasets and compare our results to existing approaches.
A Directional Occlusion Shading Model for Interactive Direct Volume Rendering
Authors: Schott Mathias , Pegoraro Vincent , Hansen Charles , Boulanger Kévin , Bouatouch Kadi 
Published: July 2009

AbstractVolumetric rendering is widely used to examine 3D scalar fields from CT/MRI scanners and numerical simulation datasets. One key aspect of volumetric rendering is the ability to provide perceptual cues to aid in understanding structure contained in the data. While shading models that reproduce natural lighting conditions have been shown to better convey depth information and spatial relationships, they traditionally require considerable (pre)computation. In this paper, a shading model for interactive direct volume rendering is proposed that provides perceptual cues similar to those of ambient occlusion, for both solid and transparent surface‐like features. An image space occlusion factor is derived from the radiative transport equation based on a specialized phase function. The method does not rely on any precomputation and thus allows for interactive explorations of volumetric data sets via on‐the‐fly editing of the shading model parameters or (multi‐dimensional) transfer functions while modifications to the volume via clipping planes are incorporated into the resulting occlusion‐based shading.
Fused Multi‐Volume DVR using Binary Space Partitioning
Authors: Lindholm Stefan , Ljung Patric , Hadwiger Markus , Ynnerman Anders 
Published: July 2009

AbstractMultiple‐volume visualization is a growing field in medical imaging providing simultaneous exploration of volumes acquired from varying modalities. However, high complexity results in an increased strain on performance compared to single volume rendering as scenes may consist of volumes with arbitrary orientations and rendering is performed with varying sample densities. Expensive image order techniques such as depth peeling have previously been used to perform the necessary calculations. In this work we present a view‐independentregion based scene descriptionfor multi‐volume pipelines. Using Binary Space Partitioning we are able to create a simple interface providing all required information for advanced multi‐volume renderings while introducing a minimal overhead for scenes with few volumes. The modularity of our solution is demonstrated by the use of visual development and performance is documented with benchmarks and real‐time simulations.
Accelerating Volume Raycasting using Proxy Spheres
Authors: Liu B. , Clapworthy G. J. , Dong F. 
Published: July 2009

AbstractIn this paper, we propose an efficient solution that addresses the performance problems of current single‐pass GPU raycasting algorithms. Our paper provides more control over the rendering process by introducing tighter ray segments for raycasting, while at the same time avoiding the introduction of any new rendering artefacts. We achieve this by dynamically generating, on the GPU, a coarsely fitted proxy geometry, composed of spheres, for the active blocks. The spheres are then rasterised into two z‐buffers by a single rendering pass. The resulting two z‐buffers are used as the first‐hit and last‐hit points for the subsequent raycaster. With this approach, only the valid ray segments between the two z‐buffers need to be sampled during raycasting. This also provides more coherent parallelism on the GPU due to more consistent ray length and avoidance of the overheads and dynamic branching of performing checks on a per‐sample basis during the raycasting pass.Our technique is ideal for dynamic data exploration in which both the transfer function and view parameters need to be changed frequently at runtime. The rendering results of our algorithm are identical to the general cube‐based proxy geometry algorithm, but the performance can be up to 15.7 times faster. Furthermore, the approach can be adopted by any existing raycasting system in a straightforward way.
MultiClusterTree: Interactive Visual Exploration of Hierarchical Clusters in Multidimensional Multivariate Data
Authors: Van Long Tran , Linsen Lars 
Published: July 2009

AbstractVisual analytics of multidimensional multivariate data is a challenging task because of the difficulty in understanding metrics in attribute spaces with more than three dimensions. Frequently, the analysis goal is not to look into individual records but to understand the distribution of the records at large and to find clusters of records with similar attribute values. A large number of (typically hierarchical) clustering algorithms have been developed to group individual records to clusters of statistical significance. However, only few visualization techniques exist for further exploring and understanding the clustering results. We propose visualization and interaction methods for analyzing individual clusters as well as cluster distribution within and across levels in the cluster hierarchy. We also provide a clustering method that operates on density rather than individual records. To not restrict our search for clusters, we compute density in the given multidimensional multivariate space. Clusters are formed by areas of high density. We present an approach that automatically computes a hierarchical tree of high density clusters. To visually represent the cluster hierarchy, we present a 2D radial layout that supports an intuitive understanding of the distribution structure of the multidimensional multivariate data set. Individual clusters can be explored interactively using parallel coordinates when being selected in the cluster tree. Furthermore, we integrate circular parallel coordinates into the radial hierarchical cluster tree layout, which allows for the analysis of the overall cluster distribution. This visual representation supports the comprehension of the relations between clusters and the original attributes. The combination of the 2D radial layout and the circular parallel coordinates is used to overcome the overplotting problem of parallel coordinates when looking into data sets with many records. We apply an automatic coloring scheme based on the 2D radial layout of the hierarchical cluster tree encoding hue, saturation, and value of the HSV color space. The colors support linking the 2D radial layout to other views such as the standard parallel coordinates or, in case data is obtained from multidimensional spatial data, the distribution in object space.
Visualisation of Sensor Data from Animal Movement
Authors: Grundy Edward , Jones Mark W. , Laramee Robert S. , Wilson Rory P. , Shepard Emily L.C. 
Published: July 2009

AbstractA new area of biological research is identifying and grouping patterns of behaviour in wild animals by analysing data obtained through the attachment of tri‐axial accelerometers. As these recording devices become smaller and less expensive their use has increased. Currently acceleration data are visualised as 2D time series plots, and analyses are based on summary statistics and the application of Fourier transforms. We develop alternate visualisations of this data so as to analyse, explore and present new patterns of animal behaviour. Our visualisations include interactive spherical scatterplots, spherical histograms, clustering methods, and feature‐based state diagrams of the data. We study the application of these visualisation methods to accelerometry data from animal movement. The reaction of biologists to these visualisations is also reported.
The Gödel Engine ‐ An interactive approach to visualization in general relativity
Authors: Grave Frank , Müller Thomas , Dachsbacher Carsten , Wunner Günter 
Published: July 2009

AbstractWe present a methodical new approach to visualize the aspects of general relativity from a self‐centered perspective. We focus on the visualization of the Gödel universe, which is an exact solution to Einstein's field equations of general relativity. This model provides astounding features such as the existence of an optical horizon and the possibility of time travel. Although we know that our universe is not of Gödel type, we can – using this solution to Einstein's equations – visualize and understand the effects resulting from the theory of relativity, which itself has been verified on the large scale in numerous experiments over the last century. We derive the analytical solution to the geodesic equations of Gödel's universe for special initial conditions. Along with programmable graphics hardware we achieve a tremendous speedup for the visualization of general relativity. This enables us to interactively explore the physical aspects and optical effects of Gödel's universe. We also demonstrate how the analytical solution enables dynamic lighting with local illumination models. Our implementation is tailored for Gödel's universe and five orders of magnitude faster than previous approaches. It can be adapted to manifolds for which an analytical expression of the propagation of light is available.
Direct Visualization of Deformation in Volumes
Authors: Busking Stef , Botha Charl P. , Post Frits H. 
Published: July 2009

AbstractDeformation is a topic of interest in many disciplines. In particular in medical research, deformations of surfaces and even entire volumetric structures are of interest. Clear visualization of such deformations can lead to important insight into growth processes and progression of disease.We present new techniques for direct focus+context visualization of deformation fields representing transformations between pairs of volumetric datasets. Typically, such fields are computed by performing a non‐rigid registration between two data volumes. Our visualization is based on direct volume rendering and uses the GPU to compute and interactively visualize features of these deformation fields in real‐time. We integrate visualization of the deformation field with visualization of the scalar volume affected by the deformations. Furthermore, we present a novel use of texturing in volume rendered visualizations to show additional properties of the vector field on surfaces in the volume.