EuroVisShort2015

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https://diglib.eg.org/handle/10.2312/12463

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Ambient Grids: Maintain Context-Awareness via Aggregated Off-Screen Visualization
(The Eurographics Association, 2015) Jäckle, Dominik; Stoffel, Florian; Kwon, Bum Chul; Sacha, Dominik; Stoffel, Andreas; Keim, Daniel A.; E. Bertini and J. Kennedy and E. Puppo
When exploring large spatial datasets, zooming and panning interactions often lead to the loss of contextual overview. Existing overview-plus-detail approaches allow users to view context while inspecting details, but they often suffer from distortion or overplotting. In this paper, we present an off-screen visualization method called Ambient Grids that strikes the balance between overview and details by preserving the contextual information as color grids within a designated space around the focal area. In addition, we describe methods to generate Ambient Grids for point data using data aggregation and projection. In a use case, we show the usefulness of our technique in exploring the VAST Challenge 2011 microblog dataset.
Analyzing the Evolution of the Internet
(The Eurographics Association, 2015) Johnson, Thienne; Acedo, Carlos; Kobourov, Stephen; Nusrat, Sabrina; E. Bertini and J. Kennedy and E. Puppo
Existing representations of the Internet do not provide information on why countries have a bigger Internet presence (e.g., Internet Service Providers) than others. In this paper we evaluate four geo-economic parameters (area, population, GDP and GDP per capita), looking for clues of why some areas or countries have developed earlier/ later, faster/slower than others. We use correlation studies to analyze which geo-economic variable leads to bigger development in the Internet infrastructure per continent, and cartograms to represent the growth of the Internet infrastructure around the world, in a sequence of 24 years. These representations make it possible to find interesting patterns and identify outliers.
Bridging the Gap of Domain and Visualization Experts with a Liaison
(The Eurographics Association, 2015) Simon, Svenja; Mittelstädt, Sebastian; Keim, Daniel A.; Sedlmair, Michael; E. Bertini and J. Kennedy and E. Puppo
We introduce the role Liaison for design study projects. With considerable expertise in visualization and the application domain, a Liaison can help to foster richer and more effective interdisciplinary communication in problem characterization, design, and evaluation processes. We characterize this role, provide a list of tasks of Liaison and visualization experts, and discuss concrete benefits and potential limitations based on our experience from multiple design studies. To illustrate our contributions we use as an example a molecular biology design study.
Card Sorting Techniques for Domain Characterization in Problem-driven Visualization Research
(The Eurographics Association, 2015) Sakai, Ryo; Aerts, Jan; E. Bertini and J. Kennedy and E. Puppo
In a problem-driven visualization research, the domain characterization is fundamental to the design process of a visualization solution to enable insight and discovery. Complex, fuzzy and exploratory analysis tasks in a specialized domain present considerable challenges to the designer, as well as the expert, to establish a shared understanding of the domain problem and analysis needs. In this paper, we provide a three-stage practical guideline for conducting card sorting exercise to address challenges in the domain characterization and a case study from the biological domain.
Clustering Moment Invariants to Identify Similarity within 2D Flow Fields
(The Eurographics Association, 2015) Bujack, Roxana; Kasten, Jens; Natarajan, Vijay; Scheuermann, Gerik; Joy, Kenneth I.; E. Bertini and J. Kennedy and E. Puppo
Moment invariants have proven to be a useful tool for the detection of patterns in scalar and vector fields. By their means, an interesting feature can be detected in a data set independent of its exact orientation, position, and scale. In this paper, we show that they can also be applied to explore an unknown dataset without prior determination of a query feature pattern it may possibly contain. The clustering of the high dimensional moment space reveals the major structures in the underlying flow field and gives an excellent overview for subsequent more profound exploration.
ColorCAT: Guided Design of Colormaps for Combined Analysis Tasks
(The Eurographics Association, 2015) Mittelstädt, Sebastian; Jäckle, Dominik; Stoffel, Florian; Keim, Daniel A.; E. Bertini and J. Kennedy and E. Puppo
Colormap design is challenging because the encoding must match the requirements of data and analysis tasks as well as the perception of the target user. A number of well-known tools exist to support the design of colormaps. ColorBrewer [HB03], for example, is a great resource to select colors for qualitative, sequential, and diverging data. PRAVDAColor [BRT95] and Tominski et al. [TFS08], for example, provide valuable guidelines for single analysis tasks such as localization, identification, and comparison. However, for solving real world problems in most practical applications, single elementary analysis tasks are not sufficient but need to be combined. In this paper, we propose a methodology and tool to design colormaps for combined analysis tasks. We define color mapping requirements and develop a set of design guidelines. The visualization expert is integrated in the design process to incorporate his/her design requirements, which may depend on the application, culture, and aesthetics. Our ColorCAT tool guides novice and expert designers through the creation of colormaps and allows the exploration of the design space of color mapping for combined analysis tasks.
Dynamic Scheduling for Progressive Large-Scale Visualization
(The Eurographics Association, 2015) Flatken, Markus; Berres, Anne; Merkel, Jonas; Hotz, Ingrid; Gerndt, Andreas; Hagen, Hans; E. Bertini and J. Kennedy and E. Puppo
The ever-increasing compute capacity of high-performance systems enables scientists to simulate physical phenomena with a high spatial and temporal accuracy. Thus, the simulation output can yield dataset sizes of many terabytes. An efficient analysis and visualization process becomes very difficult especially for explorative scenarios where users continuously change input parameters. Using a distributed rendering pipeline may relieve the visualization frontend considerably but is often not sufficient. Therefore, we additionally propose a progressive data streaming and rendering approach. The main contribution of our method is the importance-guided order of data processing for block structured datasets. This requires a dynamic scheduling of data chunks on the parallel post-processing system which has been implemented by using an R-Tree. In this paper, we demonstrate the efficiency of our implementation for view-dependent feature extraction with varying viewpoints.
Exploratory Performance Analysis and Tuning of Parallel Interactive Volume Visualization on Large Displays
(The Eurographics Association, 2015) Panagiotidis, Alexandros; Frey, Steffen; Ertl, Thomas; E. Bertini and J. Kennedy and E. Puppo
We present an exploratory approach to performance analysis and tuning of interactive parallel volume visualization for large displays. While traditional approaches target non-interactive applications and focus on separate specialized views for post-mortem performance analysis, we show metrics from the GPU and volume ray casting together with the volume visualization and allow users to interact with both of them simultaneously. With this, users can explore the data set together with the corresponding metrics to investigate both the visual and the performance impact of different parameter settings jointly, like camera position, sampling density, or acceleration technique. In particular, this supports parameter tuning by providing the user not only with timings and quality measures, but also internal metrics from the GPU and the ray caster that help to understand the connection between parameter settings and their induced outcome. We demonstrate the usage and utility of our approach for performance analysis and tuning at the example of distributed volume ray casting for a high-resolution powerwall with the goal to achieve interactive frame rates with the best possible image quality.
Exploratory Text Analysis using Lexical Episode Plots
(The Eurographics Association, 2015) Gold, Valentin; Rohrdantz, Christian; El-Assady, Mennatallah; E. Bertini and J. Kennedy and E. Puppo
In this paper, we present Lexical Episode Plots, a novel automated text-mining and visual analytics approach for exploratory text analysis. In particular, we first describe an algorithm for automatically annotating text regions to examine prominent themes within natural language texts. The algorithm is based on lexical chaining to find spans of text in which the frequency of a term is significantly higher than its average in the document. In a second step we present an interactive visualization supporting the exploration and interpretation of Lexical Episodes. The visualization links higher-level thematic structures with content-level details. The methodological capabilities of our approach are illustrated by analyzing the televised US presidential election debates.
Frontmatter: Eurographics Conference on Visualization (EuroVis) 2015 - Short Papers
(Eurographics Association, 2015) Bertini, Enrico; Kennedy, Jessie; Puppo, Enrico; -
Improved Sparse Seeding for 3D Electrostatic Field Lines
(The Eurographics Association, 2015) Scharnowski, Katrin; Boblest, Sebastian; Ertl, Thomas; E. Bertini and J. Kennedy and E. Puppo
We present an improved seeding strategy for sparse visualization of electrostatic fields. By analyzing the curvature of the field lines, we extract points of extremal field strength between charges of different sign and use them to seed field lines, which consequently connect the corresponding charges. The resulting sparse representation can be seen as an extension to classic vector field topology depicting properties otherwise hidden. Finally, by applying our method to a synthetic data set, we show its benefits over previously published work.
Interaction with Uncertainty in Visualisations
(The Eurographics Association, 2015) Sarkar, Advait; Blackwell, Alan F.; Jamnik, Mateja; Spott, Martin; E. Bertini and J. Kennedy and E. Puppo
In recent years, a number of algorithms have been developed which provide fast approximate computations on large datasets. There is considerable interest in exploiting these techniques to render interactive visualisations of large datasets. Such interactions require careful consideration of the uncertainty arising from the approximations that these algorithms employ. Characterising and comparing visualisations of uncertainty has been well studied; however, it is typically assumed that uncertainty is a fixed property of the data. In light of this new generation of approximate visualisations, we consider the case where uncertainty arises from algorithms whose parameters can be altered, and so can be manipulated just like any other aspect of the visualisation. We present a novel directmanipulation interface for uncertainty in visualisations and show through a user study that our interface enables people to successfully edit and comprehend uncertainty.
OceanPaths: Visualizing Multivariate Oceanography Data
(The Eurographics Association, 2015) Nobre, Carolina; Lex, Alexander; E. Bertini and J. Kennedy and E. Puppo
Geographical datasets are ubiquitous in oceanography. While map-based visualizations are useful for many different domains, they can suffer from cluttering and overplotting issues when used for multivariate data sets. As a result, spatial data exploration in oceanography has often been restricted to multiple maps showing various depths or time intervals. This lack of interactive exploration often hinders efforts to expose correlations between properties of oceanographic features, specifically currents. OceanPaths provides powerful interaction and exploration methods for spatial, multivariate oceanography datasets to remedy these situations. Fundamentally, our method allows users to define pathways, typically following currents, along which the variation of the high-dimensional data can be plotted efficiently. We present a case study conducted by domain experts to underscore the usefulness of OceanPaths in uncovering trends and correlations in oceanographic data sets.
PoPI: Glyph Designs for Collaborative Filtering on Interactive Tabletops
(The Eurographics Association, 2015) Charleer, Sven; Klerkx, Joris; Duval, Erik; E. Bertini and J. Kennedy and E. Puppo
Filtering data on a visualization can be a challenge when multiple people work on a shared visualization, for instance on an interactive tabletop. Visualizations can present data that satisfy the union of all user filters, or data lenses can provide individual views on parts of the data. To support per-user filters simultaneously across a shared visualization, we explore different glyph approaches that complement data points with per-user filter status information. Adding physical positions of users around the tabletop as an extra attribute to the glyph, we attempt to lower the cognitive load required to map filter statuses to corresponding participants. This work presents the design choices, briefly covers technical development, reports on the evaluation results and points out possibilities for future work.
A Quality-Preserving Cartesian to Body-Centered Cubic Downsampling Transform
(The Eurographics Association, 2015) Alim, Usman R.; Oliveira, Thiago Valentin de; E. Bertini and J. Kennedy and E. Puppo
The body-centered cubic lattice is the optimal sampling lattice in three dimensions. However, most volumetric datasets are acquired on the well-known Cartesian cubic lattice. In order to leverage the approximation capabilities of the body-centred cubic lattice, we propose a factor-of-four Cartesian to body-centered downsampling transform. We derive a Fourier domain post-aliasing error kernel and use it to optimize the cosine-weighted trilinear B-spline kernel. We demonstrate that our downsampling transform preserves fidelity when an oversampled function of interest is reconstructed with trilinear interpolation on the fine-scale Cartesian grid, and optimized cosine-weighted trilinear approximation on the coarse-scale body-centered cubic grid.
State of the Art in Mobile Volume Rendering on iOS Devices
(The Eurographics Association, 2015) Schiewe, Alexander; Anstoots, Mario; Krüger, Jens; E. Bertini and J. Kennedy and E. Puppo
The ubiquity of ever-increasing computing power with mobile devices has put last generation desktop-grade hardware in everyone's palms. Mobile computing hardware is rapidly approaching today's desktop-grade hardware capabilities enabling applications of advanced rendering algorithms to previously untouched environments such as medical care. Recent developments in graphics APIs have introduced novel low-level APIs such as AMD's Mantle API for desktops and Apple's Metal API for mobile hardware. Microsoft's DirectX 12 and the OpenGL successor Vulkan will be available in the near future. AAA game titles were announced for which publishers see an advantage-as promised by the creators of the new APIs-over traditional portable implementations. The new APIs are mostly advertised to allow for more draw-calls per frame compared to for example, OpenGL-based solutions. Visualization algorithms and in particular direct volume rendering do not exhibit a significant amount of draw-calls as a bottleneck. This work evaluates and highlights the utility of recent low-level APIs for mobile devices and puts them into perspective with available alternatives.
Task Taxonomy for Cartograms
(The Eurographics Association, 2015) Nusrat, Sabrina; Kobourov, Stephen; E. Bertini and J. Kennedy and E. Puppo
Cartograms are maps in which areas of geographic regions (countries, states) appear in proportion to some variable of interest (population, income). Despite the popularity of cartograms and the large number of cartogram variants, there are few studies evaluating the effectiveness of cartograms in conveying information. In order to design cartograms as a useful visualization tool and to be able to compare the effectiveness of cartograms generated by different methods, we need to study the nature of information conveyed and the specific tasks that can be performed on cartograms. In this paper we consider a set of cartogram visualization tasks, based on standard taxonomies from cartography and information visualization. We then propose a cartogram task taxonomy that can be used to organize not only the tasks considered here but also other tasks that might be added later.
A Testbed Combining Visual Perception Models for Geographic Gaze Contingent Displays
(The Eurographics Association, 2015) Bektas, Kenan; Cöltekin, Arzu; Krüger, Jens; Duchowski, Andrew T.; E. Bertini and J. Kennedy and E. Puppo
We present a testbed featuring gaze-contingent displays (GCDs), in which we combined multiple models of the human visual system (HVS) to manage the visual level of detail. GCDs respond to the viewer's gaze in real-time, rendering a space-variant visualization. Our testbed is optimized for testing mathematical models of the human visual perception utilized in GCDs. Specifically, we combined models of contrast sensitivity, color perception and depth of field; and customized our implementation for geographic imagery. In this customization process, similarly to the geographic information systems (GIS), we georeference the input images, add vector layers on demand, and enable stereo viewing. After the implementation, we studied the computational and perceptual benefits of the studied perceptual models in terms of data reduction and user experience in geographic information science (GIScience) domain. Our computational validation experiments and the user study results indicate the HVS-based data reduction solutions are competitive, and encourage further research. We believe the research outcome and the testbed will be relevant in domains where visual interpretation of imagery is a part of professional life; such as in search and rescue, damage assessment in hazards, geographic image interpretation or urban planning.
Towards Understanding Enjoyment and Flow in Information Visualization
(The Eurographics Association, 2015) Saket, Bahador; Scheidegger, Carlos; Kobourov, Stephen G.; E. Bertini and J. Kennedy and E. Puppo
Traditionally, evaluation studies in information visualization have measured effectiveness by assessing performance time and accuracy. More recently, there has been a concerted effort to understand aspects beyond time and errors. In this paper we study enjoyment, which, while arguably not the primary goal of visualization, has been shown to impact performance and memorability. Different models of enjoyment have been proposed in other fields; yet there is no standard approach to evaluate and measure enjoyment in visualization. In this paper we attempt to relate the flow model of Csikszentmihalyi to Munzner's nested model of visualization evaluation and previous work in the area. We suggest that, even though previous papers tackled individual elements of flow, in order to understand what specifically makes a visualization enjoyable, it might be necessary to measure specific elements in particular ways.
Visual Analytics of Work Behavior Data - Insights on Individual Differences
(The Eurographics Association, 2015) Koldijk, Saskia; Bernard, Jürgen; Ruppert, Tobias; Kohlhammer, Jörn; Neerincx, Mark; Kraaij, Wessel; E. Bertini and J. Kennedy and E. Puppo
Stress in working environments is a recent concern. We see potential in collecting sensor data to detect patterns in work behavior with potential danger to well-being. In this paper, we describe how we applied visual analytics to a work behavior dataset, containing information on facial expressions, postures, computer interactions, physiology and subjective experience. The challenge is to interpret this multi-modal low level sensor data. In this work, we alternate between automatic analysis procedures and data visualization. Our aim is twofold: 1) to research the relations of various sensor features with (stress related) mental states, and 2) to develop suitable visualization methods for insight into a large amount of behavioral data. Our most important insight is that people differ a lot in their (stress related) work behavior, which has to be taken into account in the analyses and visualizations.

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