Eurovis: Eurographics Conference on Visualization

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https://diglib.eg.org/handle/10.2312/392

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2D Vector Field Visualization Using Furlike Texture
(Springer and The Eurographics Association, 1999) Khouas, Leila; Odet, Christophe; Friboulet, Denis; Gröller, E., Löffelmann, H., Ribarsky, W.
This paper presents a new technique for 2D vector field visualization. Our approach is based on the use of a furlike texture. For this purpose, we have first developed a texture model that allows two dimensional synthesis of 3D furlike texture. The technique is based on a non stationary two dimensional Autoregressive synthesis (2D AR). The texture generator allows local control of orientation and length of the synthesized texture (the orientation and length of filaments). This texture model is then used to represent 2D vector fields. We can use orientation, length, density and color attributes of our furlike texture to visualize local orientation and magnitude of a 2D vector field. The visual representations produced are satisfying since complete information about local orientation is easily perceived. We will show that the technique can also produce LIC-like texture. In addition, due to the AR formulation, the obtained technique is computationally efficient.
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.
4D MRI Flow Coupled to Physics-Based Fluid Simulation for Blood-Flow Visualization
(The Eurographics Association and John Wiley and Sons Ltd., 2014) Hoon, Niels de; Pelt, Roy van; Jalba, Andrei; Vilanova, Anna; H. Carr, P. Rheingans, and H. Schumann
Modern MRI measurements deliver volumetric and time-varying blood-flow data of unprecedented quality. Visual analysis of these data potentially leads to a better diagnosis and risk assessment of various cardiovascular diseases. Recent advances have improved the speed and quality of the imaging data considerably. Nevertheless, the data remains compromised by noise and a lack of spatiotemporal resolution. Besides imaging data, also numerical simulations are employed. These are based on mathematical models of specific features of physical reality. However, these models require realistic parameters and boundary conditions based on measurements. We propose to use data assimilation to bring measured data and physically-based simulation together, and to harness the mutual benefits. The accuracy and noise robustness of the coupled approach is validated using an analytic flow field. Furthermore, we present a comparative visualization that conveys the differences between using conventional interpolation and our coupled approach.
Abstractive Representation and Exploration of Hierarchically Clustered Diffusion Tensor Fiber Tracts
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Chen, Wei; Zhang, Song; Correia, Stephen; Ebert, David S.; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Diffusion tensor imaging (DTI) has been used to generate fibrous structures in both brain white matter and muscles. Fiber clustering groups the DTI fibers into spatially and anatomically related tracts. As an increasing number of fiber clustering methods have been recently developed, it is important to display, compare, and explore the clustering results efficiently and effectively. In this paper, we present an anatomical visualization technique that reduces the geometric complexity of the fiber tracts and emphasizes the high-level structures. Beginning with a volumetric diffusion tensor image, we first construct a hierarchical clustering representation of the fiber bundles. These bundles are then reformulated into a 3D multi-valued volume data. We then build a set of geometric hulls and principal fibers to approximate the shape and orientation of each fiber bundle. By simultaneously visualizing the geometric hulls, individual fibers, and other data sets such as fractional anisotropy, the overall shape of the fiber tracts are highlighted, while preserving the fibrous details. A rater with expert knowledge of white matter structure has evaluated the resulting interactive illustration and confirmed the improvement over straightforward DTI fiber tract visualization.
Accelerated Force Computation for Physics-Based Information Visualization
(The Eurographics Association, 2003) Hao, Ming C.; Dayal, Umeshwar; Cotting, Daniel; Holenstein, Thomas; Gross, Markus; G.-P. Bonneau and S. Hahmann and C. D. Hansen
Visualization of similarity is an emerging technique for analyzing relation-based data sets. A common way of computing the respective layouts in an information space is to employ a physics-based mass-spring system. Force computation, however, is costly and of order N2. In this paper, we propose a new acceleration method to adopt a well-known optimized force-computation algorithm which drastically reduces the computation time to the order of N log N. The basic idea is to derive a two-pass, "prediction and correction" procedure including a customized potential function. We have applied this method to two different applications: web access and sales analysis. Both demonstrate the efficiency and versatility of the presented method.
Accelerated Visualization of Dynamic Molecular Surfaces
(The Eurographics Association and Blackwell Publishing Ltd., 2010) Lindow, Norbert; Baum, Daniel; Prohaska, Steffen; Hege, Hans-Christian; G. Melancon, T. Munzner, and D. Weiskopf
Molecular surfaces play an important role in studying the interactions between molecules. Visualizing the dynamic behavior of molecules is particularly interesting to gain insights into a molecular system. Only recently it has become possible to interactively visualize dynamic molecular surfaces using ray casting techniques. In this paper, we show how to further accelerate the construction and the rendering of the solvent excluded surface (SES) and the molecular skin surface (MSS). We propose several improvements to reduce the update times for displaying these molecular surfaces. First, we adopt a parallel approximate Voronoi diagram algorithm to compute the MSS. This accelerates the MSS computation by more than one order of magnitude on a single core. Second, we demonstrate that the contour-buildup algorithm is ideally suited for computing the SES due to its inherently parallel structure. For both parallel algorithms, we observe good scalability up to 8 cores and, thus, obtain interactive frame rates for molecular dynamics trajectories of up to twenty thousand atoms for the SES and up to a few thousand atoms for the MSS. Third, we reduce the rendering time for the SES using tight-fitting bounding quadrangles as rasterization primitives. These primitives also accelerate the rendering of the MSS. With these improvements, the interactive visualization of the MSS of dynamic trajectories of a few thousand atoms becomes for the first time possible. Nevertheless, the SES remains a few times faster than the MSS.
Accelerating Volume Raycasting using Proxy Spheres
(The Eurographics Association and Blackwell Publishing Ltd., 2009) Liu, Baoquan; Clapworthy, Gordon J.; Dong, Feng; H.-C. Hege, I. Hotz, and T. Munzner
In 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.
Accuracy Evaluation of Different Centerline Approximations of Blood Vessels
(The Eurographics Association, 2004) Cruz, A. La; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
Accurate determination of the vessel axis is a prerequisite for automated visualization and quantification of artery diseases. This paper presents an evaluation of different methods for approximating the centerline of the vessel in a phantom simulating the peripheral arteries. Six algorithms were used to determine the centerline of a synthetic peripheral arterial vessel. They are based on: ray casting using thresholds and maximum gradient-like stop criterion, pixel motion estimation between successive images called block matching, center of gravity and shape based segmentation. The Randomized Hough Transform and ellipse fitting have been used as shape based segmentation techniques. Since in the synthetic data set the centerline is known, an estimation of the error can be calculated in order to determine the accuracy achieved by a given method.
Acquisition and Display of Real-Time Atmospheric Data on Terrain
(The Eurographics Association, 2001) Jiang, Tian-yue; Ribarsky, William; Wasilewski, Tony; Faust, Nickolas; Hannigan, Brendan; Parry, Mitchell; David S. Ebert and Jean M. Favre and Ronald Peikert
This paper investigates the integrated acquisition, organization, and display of data from disparate sources, including the display of data acquired in real-time. In this case real-time acquisition and display refers to the capture and visualization of data as they are being produced. The particular application investigated is 3D dynamic atmospheric data on terrain, but key elements presented here are applicable more generally to other types of real-time data. 3D Doppler radar data are acquired and visualized with global, high resolution terrain. This is the first time such data have been displayed together in a real-time environment and provides the potential for new vistas in forecasting and analysis. Associated data such as buildings and maps are displayed along with the weather data and the terrain. A global hierarchical structure makes these disparate data available for integrated visualization in real-time. Requirements for effective 3D visualization for decision-making are identified, and it is shown that the applications presented meet most of these requirements.
Adaptive Recommendations for Enhanced Non-linear Exploration of Annotated 3D Objects
(The Eurographics Association and John Wiley & Sons Ltd., 2015) Rodriguez, Marcos Balsa; Agus, Marco; Marton, Fabio; Gobbetti, Enrico; H. Carr, K.-L. Ma, and G. Santucci
We introduce a novel approach for letting casual viewers explore detailed 3D models integrated with structured spatially associated descriptive information organized in a graph. Each node associates a subset of the 3D surface seen from a particular viewpoint to the related descriptive annotation, together with its author-defined importance. Graph edges describe, instead, the strength of the dependency relation between information nodes, allowing content authors to describe the preferred order of presentation of information. At run-time, users navigate inside the 3D scene using a camera controller, while adaptively receiving unobtrusive guidance towards interesting viewpoints and history- and location-dependent suggestions on important information, which is adaptively presented using 2D overlays displayed over the 3D scene. The capabilities of our approach are demonstrated in a real-world cultural heritage application involving the public presentation of sculptural complex on a large projection-based display. A user study has been performed in order to validate our approach.
Adaptive Smooth Scattered-data Approximation for Large-scale Terrain Visualization
(The Eurographics Association, 2003) Bertram, Martin; Tricoche, Xavier; Hagen, Hans; G.-P. Bonneau and S. Hahmann and C. D. Hansen
We present a fast method that adaptively approximates large-scale functional scattered data sets with hierarchical B-splines. The scheme is memory efficient, easy to implement and produces smooth surfaces. It combines adaptive clustering based on quadtrees with piecewise polynomial least squares approximations. The resulting surface components are locally approximated by a smooth B-spline surface obtained by knot removal. Residuals are computed with respect to this surface approximation, determining the clusters that need to be recursively refined, in order to satisfy a prescribed error bound. We provide numerical results for two terrain data sets, demonstrating that our algorithm works efficiently and accurate for large data sets with highly non-uniform sampling densities.
Adaptive Volume Construction from Ultrasound Images of a Human Heart
(The Eurographics Association, 2004) Reis, Gerd; Bertram, Martin; Lengen, Rolf H. van; Hagen, Hans; Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe
We present a volume modelling approach based on sequences of two-dimensional ultrasound images. Though generally applicable to arbitrary freehand ultrasound, our method is designed for the reconstruction of timevarying volumes from ultrasound images of a human heart. Since the reliability of the reconstructed data depends very much on the spatial density of ultrasound images, we apply a hierarchical modelling approach. The volume produced for each time step is represented as adaptive mesh refinement (AMR) data such that regions of low reliability in the reconstructed volume can be recognized by their coarse resolution.
Adaptive Volume Rendering using Fuzzy Logic Control
(The Eurographics Association, 2001) Li, Xinyue; Shen, Han-Wei; David S. Ebert and Jean M. Favre and Ronald Peikert
This paper presents an automatic error tolerance specification system to control the performance of hierarchical volume rendering. Rather than requiring the user to provide an explicit error tolerance numerically, we let the user to specify only the target rendering speed. Our system can then calculate an appropriate error tolerance adaptively to satisfy the user s performance goal. The system is realized using fuzzy logic control, which enables run-time adaptation based on iterative feedback control and knowledge acquired from past experience. We describe the process of constructing the fuzzy logic control system, and show that the system can successfully steer the performance of volume rendering.
Adaptively Adjusting Marching Cubes Output to Fit A Trilinear Reconstruction Filter
(The Eurographics Association, 1998) Allamandri, Fabio; Cignoni, Paolo; Montani, Claudio; Scopigno, Roberto; Bartz, Dirk
The paper focuses on the improvement of the quality of isosurfaces fitted on volume datasets with respect to standard MC solutions. The new solution presented improves the precision in the reconstruction process using an approach based on mesh re nement and driven by the evaluation of the trilinear reconstruction filter. The iso-surface reconstruction process is adaptive, to ensure that the complexity of the fitted mesh will not become excessive. The proposed approach has been tested on many datasets; we discuss the precision of the obtained meshs and report data on fitted meshes complexity and processing times.
Adding a scalar value to texture-based vector field representations by local contrast analysis
(The Eurographics Association, 2002) Sanna, A.; Zunino, C.; Montrucchio, B.; Montuschi, P.; D. Ebert and P. Brunet and I. Navazo
Several algorithms can effectively represent vector fields by texture-based representations, visualizing at most all information on the field: direction, orientation, and local magnitude. An open problem still remains the mapping on textures of adjunctive information such as temperature, pressure, and so on, without using colors. This article addresses this issue by proposing a technique to add a scalar value denoting streamlines by means of different levels of contrast. Both streamline starting tones and the range of tones depend on the scalar value to be mapped; in this way, areas visualized by different contrast levels are represented. Two examples show the effectiveness of the proposed technique.
Advances in Quality Control of Intraoperative Radiotherapy
(Springer and The Eurographics Association, 1999) Walter, Stefan; Straßmann, Gerd; Schmitt, Marco; Gröller, E., Löffelmann, H., Ribarsky, W.
Intraoperative radiotherapy is the kind of radiotherapy where the remains of a surgically not completely removed tumour are irradiated at the open situ of the patient. The current main drawback of this radiotherapy is the insufficient documentation of the applied radiation and the lack of a possibility for an individual treatment planning. This work presents a system that is a conmlon development of Fraunhofer IGD, Städtische Klinik Offenbach and MedCom GmbH which offers a possibility for supervision of the placement of the irradiation flabs through interactive navigation in eT data acquired from the patient, the creation of a documentation of the applied isodose as well as the possibility for an individual treatment planning.
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.
Alleviating the Modifiable Areal Unit Problem within Probe-Based Geospatial Analyses
(The Eurographics Association and Blackwell Publishing Ltd., 2010) Butkiewicz, Thomas; Meentemeyer, Ross K.; Shoemaker, Douglas A.; Chang, Remco; Wartell, Zachary; Ribarsky, William; G. Melancon, T. Munzner, and D. Weiskopf
We present a probe-based interface for the exploration of the results of a geospatial simulation of urban growth. Because our interface allows the user great freedom in how they choose to define regions-of-interest to examine and compare, the classic geospatial analytic issue known as the modifiable areal unit problem (MAUP) quickly arises. The user may delineate regions with unseen differences that can affect the fairness of the comparisons made between them. To alleviate this problem, our interface first alerts the user if it detects any potential unfairness between regions when they are selected for comparison. It then presents the dimensions with potential problematic outliers to the user for evaluation. Finally, it provides a number of semi-automated tools to assist the user in correcting their regions boundaries to minimize the inequalities they feel could significantly impact their comparisons.
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.
AlVis - An Aluminium-Foam Visualization and Investigation Tool
(The Eurographics Association, 2000) König, Andreas H.; Doleisch, Helmut; Kottar, Andreas; Kriszt, Brigitte; Gröller, Eduard; W. de Leeuw and R. van Liere
In recent years there has been an increased interest in metal foams in the field of material science. The stress absorbing potential is one of the most interesting properties for the application of aluminium foam (e.g. car manufacturing). Material scientists need to investigate the structure of metal foams in order to optimize their deformation behavior. An interactive tool for the investigation is presented in this work. Real-time surface rendering, automatic parameter determination, and display of local and global foam properties enable the user to understand the complex structure of the metal foam.

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