EuroVisShort2013

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https://diglib.eg.org/handle/10.2312/989

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3D Strokes on Visible Structures in Direct Volume Rendering
(The Eurographics Association, 2013) Wiebel, Alexander; Preis, Philipp; Vos, Frans M.; Hege, Hans-Christian; Mario Hlawitschka and Tino Weinkauf
In this paper we describe VisiTrace, a novel technique to draw 3D lines in direct volume rendered images. It allows to draw strokes in the 2D space of the screen to produce 3D lines that run on top or in the center of structures visible in the rendering. It is able to ignore structures that shortly occlude the structure that has been visible at the start of the stroke. For this purpose a shortest path algorithm finding the optimal curve in a specially designed graph is employed. We demonstrate the usefulness of the technique by applying it to image data from medicine and engineering, and show how it can be used to mark structures in the example data, and to automatically obtain good views toward these structures enabling faster navigation in the rendering.
Automatic Geometric Calibration of Projector-based Light Field Displays
(The Eurographics Association, 2013) Agus, Marco; Gobbetti, Enrico; Jaspe, Alberto; Pintore, Giovanni; Pintus, Ruggero; Mario Hlawitschka and Tino Weinkauf
We present a novel calibration method for continuous multiview (light field) projection-based displays using a single uncalibrated camera and four fiducial markers. Calibration starts from a simple parametric description of the display layout. First, individual projectors are calibrated through parametric optimization of an idealized pin- hole model. Then, the overall display and projector parameterization is globally optimized. Finally, independently for each projector, remaining errors are corrected through a rational 2D warping function. The final parame- ters are available to rendering engines to quickly compute forward and backward projections. The technique is demonstrated in the calibration of a large-scale horizontal-parallax-only 35MPixels light field display.
B:3D - Visualize Land-use Plans Interactively
(The Eurographics Association, 2013) Langbein, Max; Scheler, Inga; Ebert, Achim; Hagen, Hans; Mario Hlawitschka and Tino Weinkauf
In Europe, urban land-use plans only give a very abstract representation of possible building forms. Combined with a written statement describing all constraints, the so-called building code, architects have to start planning. This can create many problems by violating the building codes. To overcome these problems we developed a system visualizing building code violations in real-time and giving a spatial impression of the planned area by an additional output on 3D printers and 3D displays.
Extraction of Robust Voids and Pockets in Proteins
(The Eurographics Association, 2013) Sridharamurthy, Raghavendra; Doraiswamy, Harish; Patel, Siddharth; Varadarajan, Raghavan; Natarajan, Vijay; Mario Hlawitschka and Tino Weinkauf
Voids and pockets in a protein refer to empty spaces that are enclosed by the protein molecule. Existing methods to compute, measure, and visualize the voids and pockets in a protein molecule are sensitive to inaccuracies in the empirically determined atomic radii. This paper presents a topological framework that enables robust computation and visualization of these structures. Given a fixed set of atoms, voids and pockets are represented as subsets of the weighted Delaunay triangulation of atom centers. A novel notion of (e;p)-stable voids helps identify voids that are stable even after perturbing the atom radii by a small value. An efficient method is described to compute these stable voids for a given input pair of values (e;p).
HumMod Browser: An Exploratory Visualization Tool for Model Validation of Whole-Body Physiology Simulation
(The Eurographics Association, 2013) Chen, Jian; Wu, Keqin; Pruett, William A.; Hester, Robert L.; Mario Hlawitschka and Tino Weinkauf
We present HumMod Browser, a multi-scale exploratory visualization tool that lets physiologists validate human physiology simulation results. Showing correlations, exploring causality relationships, analyzing important attributes, and comparing numerous set of ensemble runs are common tasks in model validation. The lack of interactive exploration often hinders efforts to employ classical graph-visualization approaches in these tasks. Our HumMod Browser contributes to the interaction design and provides powerful multi-scale coordinated uncluttered interactive exploration based on tag-cloud visualization and a metaphorical interface. Two case studies containing more than 6000 physiology attributes suggest the usefulness of HumMod Browser in physiological simulation validation tasks.
Illustrative Rendering of Vortex Cores
(The Eurographics Association, 2013) Shafii, Sohail; Obermaier, Harald; Kolá?, Václav; Hlawitschka, Mario; Garth, Christoph; Hamann, Bernd; Joy, Kenneth I.; Mario Hlawitschka and Tino Weinkauf
Vortices are features crucial for understanding transitional and turbulent flow fields, and have often been visualized using isosurfaces, hulls, and line-like structures. However, they have not been represented in a nonphotorealistic manner that intuitively reflects their local characteristics.We introduce a novel visualization method that represents these features as illustrative vortex cores, and show how this illustrative method clearly depicts vortex properties such as direction, rotational strength, spatial extension, and underlying flow behavior simultaneously, in a fashion superior to standard visualization approaches. Our non-photorealistic visualizations leverage the axis and rotational properties of a vortex detector to depict the direction and the rotational strength of vortices, respectively. Furthermore, we extract flow behavior in the vicinity of the vortex cores to provide context for the vortices that we extract. We demonstrate the efficacy of our illustrative vortex extraction framework in two commonly used data sets by showing how they characterize the properties of the examined flow fields.
Information Retrieval Perspective to Interactive Data Visualization
(The Eurographics Association, 2013) Peltonen, Jaakko; Sandholm, Max; Kaski, Samuel; Mario Hlawitschka and Tino Weinkauf
Dimensionality reduction for data visualization has recently been formulated as an information retrieval task with a well-defined objective function. The formulation was based on preserving similarity relationships defined by a metric in the input space, and explicitly revealed the need for a tradeoff between avoiding false neighbors and missing neighbors on the low-dimensional display. In the harder case when the metric is not known, the similarity relationships need to come from the user. We formulate interactive visualization as information retrieval under uncertainty about the true similarities, which depend on the user's tacit knowledge and interests in the data. During the interaction the user points out misses and false positives on the display; based on the feedback the metric is gradually learned and the display converges to visualizing similarity relationships that correspond to the tacit knowledge of the user.
Local Data Models for Probabilistic Transfer Function Design
(The Eurographics Association, 2013) Obermaier, Harald; Joy, Kenneth I.; Mario Hlawitschka and Tino Weinkauf
A central component of expressive volume rendering is the identification of tissue or material types and their respective boundaries. To perform appropriate data classification, transfer functions can be defined in highdimensional histograms, removing restrictions of purely 1D scalar value classification. The presented work aims at alleviating the problems of interactive multi-dimensional transfer function design by coupling high-dimensional, probabilistic, data-centric segmentation with interaction in the natural 3D space of the volume. We fit variable Gaussian Mixture Models to user specified subsets of the data set, yielding a probabilistic data model of the identified material type and its sources. The resulting classification allows for efficient transfer function design and multi-material volume rendering as demonstrated in several benchmark data sets.
MLMD: Multi-Layered Visualization for Multi-Dimensional Data
(The Eurographics Association, 2013) Yu, Bowen; Liu, Richen; Yuan, Xiaoru; Mario Hlawitschka and Tino Weinkauf
In this paper, we propose and implement a multi-layered visualization technique in 3D space called Multi-Layered Visualization for Multi-Dimensional Data (MLMD) with its corresponding interaction techniques, for visualizing multi-dimensional data. Layers of point based plots are stacked and connected in a virtual visualization cube for comparison between different dimension settings. Viewed from the side, the plot layers intrinsically form parallel coordinates plots. MLMD integrates point based plots and parallel coordinates compactly so as to present more information at a time to help data investigation. Pertinent user interactions for MLMD method to enable convenient manipulation are designed. By using MLMD and its matching interaction techniques, proper dimension settings and in-depth data perception can be achieved.
Neighbor Embedding by Soft Kendall Correlation
(The Eurographics Association, 2013) Strickert, Marc; Hüllermeier, Eyke; Mario Hlawitschka and Tino Weinkauf
Correlation-based embedding of complex data relationships in a Euclidean space is studied. The proposed soft formulation of Kendall correlation allows for gradient-based optimization of scatter point neighborhood relationships for reconstructing original data neighbors. The approach is able to handle asymmetric data relations provided in the form of a general scoring matrix. Scale and shift invariance properties of correlation help circumventing typical embedding distortion artefacts in dimension reduction and data embedding scenarios.
A Novel Radial Visualization Approach for Undirected Hypergraphs
(The Eurographics Association, 2013) Kerren, Andreas; Jusufi, Ilir; Mario Hlawitschka and Tino Weinkauf
Hypergraphs are a more generalized concept of graphs where an edge typically connects multiple vertices. They are applicable to many different domains such as the representation of complex biochemical pathways or classification problems with non-empty intersections between different groups, for instance, in social network analysis. There is a need to visualize those relational data structures in such a way that a better understanding of the relationships between vertices as well as their interactive exploration is supported. This paper describes a new radial visualization technique to layout undirected hypergraphs without clutter and to provide methods of interaction and data analysis.
PointAO - Improved Ambient Occlusion for Point-based Visualization
(The Eurographics Association, 2013) Eichelbaum, Sebastian; Scheuermann, Gerik; Hlawitschka, Mario; Mario Hlawitschka and Tino Weinkauf
The visualization of large amounts of particles, glyphs, and other point-based data plays an important role in many fields of science, among them flow mechanics, molecular dynamics, and medical imaging. The proper perception of spatial structures and spatial relations in the data is crucial to the understanding. To accommodate this aspect, we utilize and improve an existing ambient occlusion approach, originally tailored towards line rendering and extend the approach to be applicable to point-based visualizations.
A Survey of Visualization Construction User Interfaces
(The Eurographics Association, 2013) Grammel, Lars; Bennett, Chris; Tory, Melanie; Storey, Margaret-Anne; Mario Hlawitschka and Tino Weinkauf
We have systematically surveyed the publications on visualization construction user interfaces that have been published in 12 major Visualization and HCI venues. We found six different visualization construction approaches (visual builder, visualization spreadsheet, textual programming, visual dataflow programming, template editor, and shelf configuration). The approaches differ in their flexibility, whether they support presentation or exploration tasks, and the spatial, temporal, and conceptual distance between the user interface (UI) and the visualization. Our results provide guidance to designers of visualization construction UIs.
Total Euler Characteristic as a Noise Measure to aid Transfer Function Design
(The Eurographics Association, 2013) Wiemker, Rafael; Mario Hlawitschka and Tino Weinkauf
For image-based, semi- or fully automated design of transfer functions for direct volume rendering, it is beneficial to have an estimation of the noise level in the rendered image. A topology-motivated noise measure is suggested based on the Euler Characteristic, i.e., on the number of islands and holes in the rendering. The effectiveness of this concept lies in the observation that the Euler Characteristic of the real objects of interest in a rendered scene is usually very low, typically orders of magnitude lower than the Euler Characteristic caused by noise. Interestingly, the Euler Characteristic, which is defined for binary images, can be computed simultaneously for all possible super level sets of an integer-valued gray-scale image in a single raster scan. An efficient algorithm for 2D and 3D is presented with computation cost as low as total variation. The Total Euler Characteristic of the super level sets is proposed as a noise level estimation, i.e., the L1-norm of the evolution curve of the Euler Characteristics for all possible isovalues. The superiority of the Total Euler Characteristic to other common noise estimation methods such as total variation and total second derivatives is demonstrated on renderings of the Marschner-Lobb phantom.
Toward Wall Function Consistent Interpolation of Flow Fields
(The Eurographics Association, 2013) Üffinger, Markus; Sadlo, Filip; Munz, Claus-Dieter; Ertl, Thomas; Mario Hlawitschka and Tino Weinkauf
In this paper we provide a first step toward simulation-consistent visualization techniques. We focus on wall functions modeling near-wall flow in computational fluid dynamics (CFD) using the law of the wall. By integrating these functions, which are effective only in cells adjacent to solid boundaries, with traditional interpolation schemes used in the interior of the domain, we obtain results that account for the simulation model. We demonstrate the advantages of our scheme using flow visualization techniques on two three-dimensional CFD examples.
Trajectory Density Projection for Vector Field Visualization
(The Eurographics Association, 2013) Kuhn, Alexander; Lindow, Norbert; Günther, Tobias; Wiebel, Alexander; Theisel, Holger; Hege, Hans-Christian; Mario Hlawitschka and Tino Weinkauf
Trajectory visualization is an important tool to capture intrinsic characteristics of vector fields. However, often this class of geometric visualization suffers from visual clutter due to the number of curves that occlude each other and may cover relevant features. Attempts trying to avoid this effect often require complex pre/post-processing for seeding, clustering, or filtering of relevant lines. In this work we present a simple, yet effective technique for rendering large amounts of trajectories, which highlights features of their projected density. The technique exploits capabilities of modern graphics hardware and avoids explicit feature extraction. We propose efficient schemes for its computation, provide suggestions for sensible parameter setups, and discuss important implementation aspects. In addition, we demonstrate the effectiveness of our approach in several application scenarios.
Visits: A Spatiotemporal Visualization of Location Histories
(The Eurographics Association, 2013) Thudt, Alice; Baur, Dominikus; Carpendale, Sheelagh; Mario Hlawitschka and Tino Weinkauf
Location histories are rapidly becoming easily collectable and offer new opportunities for personal reminiscing. However, while location history data contains both temporal and location information, maps provide the location content while downplaying temporal aspects and timelines focus on the temporal sequence, minimizing the spatial aspects. In contrast, autobiographical memories incorporate both time and location. To address this gap, we present Visits, a visualization system that puts time and location on equal footing. Our hybrid visualization technique, map-timelines, shows location histories as a sequence of visited places represented as map segments on a timeline. This shows the chronological order and the duration of stays, reveals repeated visits of the same place and preserves the fine-grained location information of the underlying data. We demonstrate a possible use of Visits for both main types of location histories, long-term lifelogging data and short-term travel logs.
Visualizing Contour Distributions in 2D Ensemble Data
(The Eurographics Association, 2013) Pfaffelmoser, Tobias; Westermann, Rüdiger; Mario Hlawitschka and Tino Weinkauf
Overlaid plots of iso-contours in individual members of a scalar ensemble field are a popular concept to visualize the data uncertainty. However, such plots do not allow inferring on the spatial cumulative probability distribution of the iso-contours, and they cannot reveal distribution characteristics like spread and topology for very large amounts of contours. In this paper, we propose a new visualization technique for iso-contours in ensemble data sets to overcome these limitations. Our technique makes no assumption about a stochastic uncertainty model, rendering it suitable for arbitrary ensemble distributions. It computes a statistical summary of the ensemble over the spatial domain, including probability density values for arbitrary domain points. From this information, the uncertainty and topology of iso-contours can be determined, as well as the variations in gradient magnitude around these contours. Since the visualization is carried out on the GPU, our approach allows analyzing even very large ensemble data sets at interactive rates.

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