RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS 6
SP 1164
TI behaviorism: a framework for dynamic data visualization
A1 Angus Graeme Forbes,
A1 Tobias Höllerer,
A1 George Legrady,
K1 Data visualization
K1 Visualization
K1 Rendering (computer graphics)
K1 Timing
K1 Data models
K1 Animation
K1 Programming
K1 Visual Design
K1 Visualization System and Toolkit Design (primary keyword)
K1 Time-varying Data
K1 Streaming Data
K1 Animation
AB While a number of information visualization software frameworks exist, creating new visualizations, especially those that involve novel visualization metaphors, interaction techniques, data analysis strategies, and specialized rendering algorithms, is still often a difficult process. To facilitate the creation of novel visualizations we present a new software framework, behaviorism, which provides a wide range of flexibility when working with dynamic information on visual, temporal, and ontological levels, but at the same time providing appropriate abstractions which allow developers to create prototypes quickly which can then easily be turned into robust systems. The core of the framework is a set of three interconnected graphs, each with associated operators: a scene graph for high-performance 3D rendering, a data graph for different layers of semantically-linked heterogeneous data, and a timing graph for sophisticated control of scheduling, interaction, and animation. In particular, the timing graph provides a unified system to add behaviors to both data and visual elements, as well as to the behaviors themselves. To evaluate the framework we look briefly at three different projects all of which required novel visualizations in different domains, and all of which worked with dynamic data in different ways: an interactive ecological simulation, an information art installation, and an information visualization technique.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.126
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.126

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS 6
SP 1386
TI Interactive Histology of Large-Scale Biomedical Image Stacks
A1 Won-Ki Jeong,
A1 J Schneider,
A1 Stephen G Turney,
A1 B E Faulkner-Jones,
A1 D Meyer,
A1 Rüdiger Westermann,
A1 R C Reid,
A1 J Lichtman,
A1 H Pfister,
K1 Microscopy
K1 Image coding
K1 Image resolution
K1 Pathology
K1 Graphics processing unit
K1 Data structures
K1 texture compression
K1 Gigapixel viewer
K1 biomedical image processing
K1 GPU
AB Histology is the study of the structure of biological tissue using microscopy techniques. As digital imaging technology advances, high resolution microscopy of large tissue volumes is becoming feasible; however, new interactive tools are needed to explore and analyze the enormous datasets. In this paper we present a visualization framework that specifically targets interactive examination of arbitrarily large image stacks. Our framework is built upon two core techniques: display-aware processing and GPU-accelerated texture compression. With display-aware processing, only the currently visible image tiles are fetched and aligned on-the-fly, reducing memory bandwidth and minimizing the need for time-consuming global pre-processing. Our novel texture compression scheme for GPUs is tailored for quick browsing of image stacks. We evaluate the usability of our viewer for two histology applications: digital pathology and visualization of neural structure at nanoscale-resolution in serial electron micrographs.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.168
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.168

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS 6
SP 1578
TI View-Dependent Streamlines for 3D Vector Fields
A1 Stéphane Marchesin,
A1 Cheng-Kai Chen,
A1 Chris Ho,
A1 Kwan-Liu Ma,
K1 Three dimensional displays
K1 Streaming media
K1 Entropy
K1 Measurement
K1 Visualization
K1 Rendering (computer graphics)
K1 View-dependent.
K1 Streamlines
K1 Vector fields
AB This paper introduces a new streamline placement and selection algorithm for 3D vector fields. Instead of considering the problem as a simple feature search in data space, we base our work on the observation that most streamline fields generate a lot of self-occlusion which prevents proper visualization. In order to avoid this issue, we approach the problem in a view-dependent fashion and dynamically determine a set of streamlines which contributes to data understanding without cluttering the view. Since our technique couples flow characteristic criteria and view-dependent streamline selection we are able achieve the best of both worlds: relevant flow description and intelligible, uncluttered pictures. We detail an efficient GPU implementation of our algorithm, show comprehensive visual results on multiple datasets and compare our method with existing flow depiction techniques. Our results show that our technique greatly improves the readability of streamline visualizations on different datasets without requiring user intervention.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.212
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.212

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1605
TI TanGeoMS: Tangible Geospatial Modeling System
A1 Brendan Harmon,
A1 Katherine Weaver,
A1 Helena Mitasova,
A1 Russel Harmon,
A1 Laura Tateosian,
A1 Brent Fogleman,
K1 visualization system
K1 geographic/geospatial visualization
K1 terrain visualization
K1 tangible user interface
K1 collaborative visualization
K1 human-computer interaction
AB We present TanGeoMS, a tangible geospatial modeling visualization system that couples a laser scanner, projector, and a flexible physical three-dimensional model with a standard geospatial information system (GIS) to create a tangible user interface for terrain data. TanGeoMS projects an image of real-world data onto a physical terrain model. Users can alter the topography of the model by modifying the clay surface or placing additional objects on the surface. The modified model is captured by an overhead laser scanner then imported into a GIS for analysis and simulation of real-world processes. The results are projected back onto the surface of the model providing feedback on the impact of the modifications on terrain parameters and simulated processes. Interaction with a physical model is highly intuitive, allowing users to base initial design decisions on geospatial data, test the impact of these decisions in GIS simulations, and use the feedback to improve their design. We demonstrate the system on three applications: investigating runoff management within a watershed, assessing the impact of storm surge on barrier islands, and exploring landscape rehabilitation in military training areas.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.202
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.202

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1613
TI FI3D: Direct-Touch Interaction for the Exploration of 3D Scientific Visualization Spaces
A1 Petra Isenberg,
A1 Pjotr Svetachov,
A1 Lingyun Yu,
A1 Maarten H. Everts,
A1 Tobias Isenberg,
K1 Direct-touch interaction
K1 wall displays
K1 3D navigation and exploration
K1 evaluation
K1 illustrative visualization
AB We present the design and evaluation of FI3D, a direct-touch data exploration technique for 3D visualization spaces. The exploration of three-dimensional data is core to many tasks and domains involving scientific visualizations. Thus, effective data navigation techniques are essential to enable comprehension, understanding, and analysis of the information space. While evidence exists that touch can provide higher-bandwidth input, somesthetic information that is valuable when interacting with virtual worlds, and awareness when working in collaboration, scientific data exploration in 3D poses unique challenges to the development of effective data manipulations. We present a technique that provides touch interaction with 3D scientific data spaces in 7 DOF. This interaction does not require the presence of dedicated objects to constrain the mapping, a design decision important for many scientific datasets such as particle simulations in astronomy or physics. We report on an evaluation that compares the technique to conventional mouse-based interaction. Our results show that touch interaction is competitive in interaction speed for translation and integrated interaction, is easy to learn and use, and is preferred for exploration and wayfinding tasks. To further explore the applicability of our basic technique for other types of scientific visualizations we present a second case study, adjusting the interaction to the illustrative visualization of fiber tracts of the brain and the manipulation of cutting planes in this context.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.157
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.157

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1623
TI A Scalable Distributed Paradigm for Multi-User Interaction with Tiled Rear Projection Display Walls
A1 Pablo Roman,
A1 Aditi Majumder,
A1 Maxim Lazarov,
K1 Tiled Displays
K1 Human-Computer Interaction
K1 Gesture-Based Interaction
K1 Multi-user interaction
K1 Distributed algorithms
AB We present the first distributed paradigm for multiple users to interact simultaneously with large tiled rear projection display walls. Unlike earlier works, our paradigm allows easy scalability across different applications, interaction modalities, displays and users. The novelty of the design lies in its distributed nature allowing well-compartmented, application independent, and application specific modules. This enables adapting to different 2D applications and interaction modalities easily by changing a few application specific modules. We demonstrate four challenging 2D applications on a nine projector display to demonstrate the application scalability of our method: map visualization, virtual graffiti, virtual bulletin board and an emergency management system. We demonstrate the scalability of our method to multiple interaction modalities by showing both gesture-based and laser-based user interfaces. Finally, we improve earlier distributed methods to register multiple projectors. Previous works need multiple patterns to identify the neighbors, the configuration of the display and the registration across multiple projectors in logarithmic time with respect to the number of projectors in the display. We propose a new approach that achieves this using a single pattern based on specially augmented QR codes in constant time. Further, previous distributed registration algorithms are prone to large misregistrations. We propose a novel radially cascading geometric registration technique that yields significantly better accuracy. Thus, our improvements allow a significantly more efficient and accurate technique for distributed self-registration of multi-projector display walls.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.128
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.128

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1587
TI Visualizing Flow Trajectories Using Locality-based Rendering and Warped Curve Plots
A1 Kwan-Liu Ma,
A1 Chad Jones,
K1 flow visualization
K1 multi-field visualization
K1 focus+context visualization
K1 coordinated linked views
AB In flow simulations the behavior and properties of particle trajectories often depend on the physical geometry containedin the simulated environment. Understanding the flow in and around the geometry itself is an important part of analyzing the data.Previous work has often utilized focus+context rendering techniques, with an emphasis on showing trajectories while simplifyingor illustratively rendering the physical areas. Our research instead emphasizes the local relationship between particle paths andgeometry by using a projected multi-field visualization technique. The correlation between a particle path and its surrounding areais calculated on-the-fly and displayed in a non-intrusive manner. In addition, we support visual exploration and comparative analysisthrough the use of linked information visualization, such as manipulatable curve plots and one-on-one similarity plots. Our techniqueis demonstrated on particle trajectories from a groundwater simulation and a computer room airflow simulation, where the flow ofparticles is highly influenced by the dense geometry.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.218
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.218

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1595
TI Superquadric Glyphs for Symmetric Second-Order Tensors
A1 Gordon L. Kindlmann,
A1 Thomas Schultz,
K1 Tensor Glyphs
K1 Stress Tensors
K1 Rate-of-Deformation Tensors
K1 Geometry Tensors
K1 Glyph Design
AB Symmetric second-order tensor fields play a central role in scientific and biomedical studies as well as in image analysis and feature-extraction methods. The utility of displaying tensor field samples has driven the development of visualization techniques that encode the tensor shape and orientation into the geometry of a tensor glyph. With some exceptions, these methods work only for positive-definite tensors (i.e. having positive eigenvalues, such as diffusion tensors). We expand the scope of tensor glyphs to all symmetric second-order tensors in two and three dimensions, gracefully and unambiguously depicting any combination of positive and negative eigenvalues. We generalize a previous method of superquadric glyphs for positive-definite tensors by drawing upon a larger portion of the superquadric shape space, supplemented with a coloring that indicates the quadratic form (including eigenvalue sign). We show that encoding arbitrary eigenvalue magnitudes requires design choices that differ fundamentally from those in previous work on traceless tensors that arise in the study of liquid crystals. Our method starts with a design of 2-D tensor glyphs guided by principles of scale-preservation and symmetry, and creates 3-D glyphs that include the 2-D glyphs in their axis-aligned cross-sections. A key ingredient of our method is a novel way of mapping from the shape space of three-dimensional symmetric second-order tensors to the unit square. We apply our new glyphs to stress tensors from mechanics, geometry tensors and Hessians from image analysis, and rate-of-deformation tensors in computational fluid dynamics.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.199
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.199

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1633
TI Projector Placement Planning for High Quality Visualizations on Real-World Colored Objects
A1 Daniel G. Aliaga,
A1 Alvin J. Law,
A1 Aditi Majumder,
K1 large and High-resolution Displays
K1 Interaction Design
K1 Mobile and Ubiquitous Visualization
AB Many visualization applications benefit from displaying content on real-world objects rather than on a traditional display (e.g., a monitor). This type of visualization display is achieved by projecting precisely controlled illumination from multiple projectors onto the real-world colored objects. For such a task, the placement of the projectors is critical in assuring that the desired visualization is possible. Using ad hoc projector placement may cause some appearances to suffer from color shifting due to insufficient projector light radiance being exposed onto the physical surface. This leads to an incorrect appearance and ultimately to a false and potentially misleading visualization. In this paper, we present a framework to discover the optimal position and orientation of the projectors for such projection-based visualization displays. An optimal projector placement should be able to achieve the desired visualization with minimal projector light radiance. When determining optimal projector placement, object visibility, surface reflectance properties, and projector-surface distance and orientation need to be considered. We first formalize a theory for appearance editing image formation and construct a constrained linear system of equations that express when a desired novel appearance or visualization is possible given a geometric and surface reflectance model of the physical surface. Then, we show how to apply this constrained system in an adaptive search to efficiently discover the optimal projector placement which achieves the desired appearance. Constraints can be imposed on the maximum radiance allowed by the projectors and the projectors' placement to support specific goals of various visualization applications. We perform several real-world and simulated appearance edits and visualizations to demonstrate the improvement obtained by our discovered projector placement over ad hoc projector placement.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.189
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.189

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP i
TI Table of Contents
K1
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.201
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.201

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP x
TI Message from the Editor-in-Chief
A1 Thomas Ertl,
K1
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.178
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.178

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP xi
TI Preface
A1 Jean-Daniel Fekete,
A1 Frank van Ham,
A1 Torsten Möller,
A1 Hanspeter Pfister,
A1 Raghu Machiraju,
K1
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.188
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.188

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP xxi
TI In Memoriam: Illuminating Our Paths - James (Jim) Joseph Thomas
A1 David J. Kasik,
A1 John Dill,
A1 David S Ebert,
K1
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.167
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.167

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP xxii
TI The 2010 Visualization Career Award
K1
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.203
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.203

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP xxiii
TI The 2010 Visualization Techinal Achievement Award
K1
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.204
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.204

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP xxiv
TI VisWeek Keynote Address
A1 Mary Hegarty,
K1
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.220
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.220

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP xxv
TI VisWeek Capstone Address
A1 Alexander S. Szalay,
K1
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.219
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.219

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP xxvii
TI Author Index and Cover Image Credits
K1
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.135
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.135

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 881
TI Necklace Maps
A1 Bettina Speckmann,
A1 Kevin Verbeek,
K1 Geographic Visualization
K1 Automated Cartography
K1 Proportional Symbol Maps
K1 Necklace Maps
AB Statistical data associated with geographic regions is nowadays globally available in large amounts and hence automated methods to visually display these data are in high demand. There are several well-established thematic map types for quantitative data on the ratio-scale associated with regions: choropleth maps, cartograms, and proportional symbol maps. However, all these maps suffer from limitations, especially if large data values are associated with small regions. To overcome these limitations, we propose a novel type of quantitative thematic map, the necklace map. In a necklace map, the regions of the underlying two-dimensional map are projected onto intervals on a one-dimensional curve (the necklace) that surrounds the map regions. Symbols are scaled such that their area corresponds to the data of their region and placed without overlap inside the corresponding interval on the necklace. Necklace maps appear clear and uncluttered and allow for comparatively large symbol sizes. They visualize data sets well which are not proportional to region sizes. The linear ordering of the symbols along the necklace facilitates an easy comparison of symbol sizes. One map can contain several nested or disjoint necklaces to visualize clustered data. The advantages of necklace maps come at a price: the association between a symbol and its region is weaker than with other types of maps. Interactivity can help to strengthen this association if necessary. We present an automated approach to generate necklace maps which allows the user to interactively control the final symbol placement. We validate our approach with experiments using various data sets and maps.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.180
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.180

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 890
TI Rethinking Map Legends with Visualization
A1 Aidan Slingsby,
A1 Jason Dykes,
A1 Jo Wood,
K1 Cartography
K1 design
K1 Digimap service
K1 legend
K1 online web mapping
K1 visualization
AB This design paper presents new guidance for creating map legends in a dynamic environment. Our contribution is a set ofguidelines for legend design in a visualization context and a series of illustrative themes through which they may be expressed. Theseare demonstrated in an applications context through interactive software prototypes. The guidelines are derived from cartographicliterature and in liaison with EDINA who provide digital mapping services for UK tertiary education. They enhance approaches tolegend design that have evolved for static media with visualization by considering: selection, layout, symbols, position, dynamismand design and process. Broad visualization legend themes include: The Ground Truth Legend, The Legend as Statistical Graphicand The Map is the Legend. Together, these concepts enable us to augment legends with dynamic properties that address specificneeds, rethink their nature and role and contribute to a wider re-evaluation of maps as artifacts of usage rather than statements offact. EDINA has acquired funding to enhance their clients with visualization legends that use these concepts as a consequence ofthis work. The guidance applies to the design of a wide range of legends and keys used in cartography and information visualization.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.191
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.191

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 900
TI SignalLens: Focus+Context Applied to Electronic Time Series
A1 Robert Kincaid,
K1 Focus+Context
K1 Lens
K1 Test and Measurement
K1 Electronic Signal
K1 Signal Processing
AB Electronic test and measurement systems are becoming increasingly sophisticated in order to match the increased complexity and ultra-high speed of the devices under test. A key feature in many such instruments is a vastly increased capacity for storage of digital signals. Storage of $10^9$ time points or more is now possible. At the same time, the typical screens on such measurement devices are relatively small. Therefore, these instruments can only render an extremely small fraction of the complete signal at any time. SignalLens uses a Focus+Context approach to provide a means of navigating to and inspecting low-level signal details in the context of the entire signal trace. This approach provides a compact visualization suitable for embedding into the small displays typically provided by electronic measurement instruments. We further augment this display with computed tracks which display time-aligned computed properties of the signal. By combining and filtering these computed tracks it is possible to easily and quickly find computationally detected features in the data which are often obscured by the visual compression required to render the large data sets on a small screen. Further, these tracks can be viewed in the context of the entire signal trace as well as visible high-level signal features. Several examples using real-world electronic measurement data are presented, which demonstrate typical use cases and the effectiveness of the design.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.193
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.193

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 908
TI MulteeSum: A Tool for Comparative Spatial and Temporal Gene Expression Data
A1 Tamara Munzner,
A1 Miriah Meyer,
A1 Angela DePace,
A1 Hanspeter Pfister,
K1 spatial data
K1 temporal data
K1 gene expression
AB Cells in an organism share the same genetic information in their DNA, but have very different forms and behavior becauseof the selective expression of subsets of their genes. The widely used approach of measuring gene expression over time froma tissue sample using techniques such as microarrays or sequencing do not provide information about the spatial position withinthe tissue where these genes are expressed. In contrast, we are working with biologists who use techniques that measure geneexpression in every individual cell of entire fruitfly embryos over an hour of their development, and do so for multiple closely-relatedsubspecies of Drosophila. These scientists are faced with the challenge of integrating temporal gene expression data with the spatiallocation of cells and, moreover, comparing this data across multiple related species. We have worked with these biologists overthe past two years to develop MulteeSum, a visualization system that supports inspection and curation of data sets showing geneexpression over time, in conjunction with the spatial location of the cells where the genes are expressed — it is the first tool tosupport comparisons across multiple such data sets. MulteeSum is part of a general and flexible framework we developed with ourcollaborators that is built around multiple summaries for each cell, allowing the biologists to explore the results of computations thatmix spatial information, gene expression measurements over time, and data from multiple related species or organisms. We justifyour design decisions based on specific descriptions of the analysis needs of our collaborators, and provide anecdotal evidence of theefficacy of MulteeSum through a series of case studies.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.137
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.137

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 918
TI Gremlin: An Interactive Visualization Model for Analyzing Genomic Rearrangements
A1 Anna Ritz,
A1 Trevor O'Brien,
A1 David Laidlaw,
A1 Benjamin Raphael,
K1 Information visualization
K1 bioinformatics
K1 insight-based evaluation.
AB In this work we present, apply, and evaluate a novel, interactive visualization model for comparative analysis of structural variants and rearrangements in human and cancer genomes, with emphasis on data integration and uncertainty visualization. To support both global trend analysis and local feature detection, this model enables explorations continuously scaled from the high-level, complete genome perspective, down to the low-level, structural rearrangement view, while preserving global context at all times. We have implemented these techniques in Gremlin, a genomic rearrangement explorer with multi-scale, linked interactions, which we apply to four human cancer genome data sets for evaluation. Using an insight-based evaluation methodology, we compare Gremlin to Circos, the state-of-the-art in genomic rearrangement visualization, through a small user study with computational biologists working in rearrangement analysis. Results from user study evaluations demonstrate that this visualization model enables more total insights, more insights per minute, and more complex insights than the current state-of-the-art for visual analysis and exploration of genome rearrangements.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.163
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.163

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 927
TI Graphical Perception of Multiple Time Series
A1 Niklas Elmqvist,
A1 Bryan McDonnel,
A1 Waqas Javed,
K1 line graphs
K1 braided graphs
K1 horizon graphs
K1 small multiples
K1 stacked graphs
K1 evaluation
K1 design guidelines
AB Line graphs have been the visualization of choice for temporal data ever since the days of William Playfair (1759-1823), but realistic temporal analysis tasks often include multiple simultaneous time series. In this work, we explore user performance for comparison, slope, and discrimination tasks for different line graph techniques involving multiple time series. Our results show that techniques that create separate charts for each time series--such as small multiples and horizon graphs--are generally more efficient for comparisons across time series with a large visual span. On the other hand, shared-space techniques--like standard line graphs--are typically more efficient for comparisons over smaller visual spans where the impact of overlap and clutter is reduced.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.162
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.162

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 935
TI Uncovering Strengths and Weaknesses of Radial Visualizations---an Empirical Approach
A1 Fabian Beck,
A1 Stephan Diehl,
A1 Michael Burch,
K1 radial visualization
K1 user study
K1 visual memory
AB Radial visualizations play an important role in the information visualization community. But the decision to choose a radial coordinate system is rather based on intuition than on scientific foundations. The empirical approach presented in this paper aims at uncovering strengths and weaknesses of radial visualizations by comparing them to equivalent ones in Cartesian coordinate systems. We identified memorizing positions of visual elements as a generic task when working with visualizations. A first study with 674 participants provides a broad data spectrum for exploring differences between the two visualization types. A second, complementing study with fewer participants focuses on further questions raised by the first study. Our findings document that Cartesian visualizations tend to outperform their radial counterparts especially with respect to answer times. Nonetheless, radial visualization seem to be more appropriate for focusing on a particular data dimension.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.209
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.209

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 943
TI How Information Visualization Novices Construct Visualizations
A1 Melanie Tory,
A1 Margaret-Anne Storey,
A1 Lars Grammel,
K1 Empirical study
K1 visualization
K1 visualization construction
K1 visual analytics
K1 visual mapping
K1 novices
AB It remains challenging for information visualization novices to rapidly construct visualizations during exploratory data analysis. We conducted an exploratory laboratory study in which information visualization novices explored fictitious sales data by communicating visualization specifications to a human mediator, who rapidly constructed the visualizations using commercial visualization software. We found that three activities were central to the iterative visualization construction process: data attribute selection, visual template selection, and visual mapping specification. The major barriers faced by the participants were translating questions into data attributes, designing visual mappings, and interpreting the visualizations. Partial specification was common, and the participants used simple heuristics and preferred visualizations they were already familiar with, such as bar, line and pie charts. We derived abstract models from our observations that describe barriers in the data exploration process and uncovered how information visualization novices think about visualization specifications. Our findings support the need for tools that suggest potential visualizations and support iterative refinement, that provide explanations and help with learning, and that are tightly integrated into tool support for the overall visual analytics process.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.164
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.164

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 953
TI eSeeTrack—Visualizing Sequential Fixation Patterns
A1 Hoi Ying Tsang,
A1 Melanie Tory,
A1 Colin Swindells,
K1 eye-tracking
K1 fixation pattern
K1 timeline
K1 tree-structured visualization
AB We introduce eSeeTrack, an eye-tracking visualization prototype that facilitates exploration and comparison of sequential gaze orderings in a static or a dynamic scene. It extends current eye-tracking data visualizations by extracting patterns of sequential gaze orderings, displaying these patterns in a way that does not depend on the number of fixations on a scene, and enabling users to compare patterns from two or more sets of eye-gaze data. Extracting such patterns was very difficult with previous visualization techniques. eSeeTrack combines a timeline and a tree-structured visual representation to embody three aspects of eye-tracking data that users are interested in: duration, frequency and orderings of fixations. We demonstrate the usefulness of eSeeTrack via two case studies on surgical simulation and retail store chain data. We found that eSeeTrack allows ordering of fixations to be rapidly queried, explored and compared. Furthermore, our tool provides an effective and efficient mechanism to determine pattern outliers. This approach can be effective for behavior analysis in a variety of domains that are described at the end of this paper.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.149
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.149

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 963
TI Evaluating the impact of task demands and block resolution on the effectiveness of pixel-based visualization
A1 Min Chen,
A1 Ian Thornton,
A1 Rita Borgo,
A1 Heike Jänicke,
A1 Tavi Murray,
A1 Karl Proctor,
K1 Pixel-based visualization
K1 evaluation
K1 user study
K1 visual search
K1 change detection.
AB Pixel-based visualization is a popular method of conveying large amounts of numerical data graphically. Application scenarios include business and finance, bioinformatics and remote sensing. In this work, we examined how the usability of such visual representations varied across different tasks and block resolutions. The main stimuli consisted of temporal pixel-based visualization with a white-red color map, simulating monthly temperature variation over a six-year period. In the first study, we included 5 separate tasks to exert different perceptual loads. We found that performance varied considerably as a function of task, ranging from 75% correct in low-load tasks to below 40% in high-load tasks. There was a small but consistent effect of resolution, with the uniform patch improving performance by around 6% relative to higher block resolution. In the second user study, we focused on a high-load task for evaluating month-to-month changes across different regions of the temperature range. We tested both CIE L*u*v* and RGB color spaces. We found that the nature of the change-evaluation errors related directly to the distance between the compared regions in the mapped color space. We were able to reduce such errors by using multiple color bands for the same data range. In a final study, we examined more fully the influence of block resolution on performance, and found block resolution had a limited impact on the effectiveness of pixel-based visualization.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.150
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.150

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 973
TI Graphical inference for infovis
A1 Heike Hofmann,
A1 Hadley Wickham,
A1 Dianne Cook,
A1 Andreas Buja,
K1 Statistics
K1 visual testing
K1 permutation tests
K1 null hypotheses
K1 data plot
AB How do we know if what we see is really there? When visualizing data, how do we avoid falling into the trap of apophenia where we see patterns in random noise? Traditionally, infovis has been concerned with discovering new relationships, and statistics with preventing spurious relationships from being reported. We pull these opposing poles closer with two new techniques for rigorous statistical inference of visual discoveries. The "Rorschach" helps the analyst calibrate their understanding of uncertainty and "line-up" provides a protocol for assessing the significance of visual discoveries, protecting against the discovery of spurious structure.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.161
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.161

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 980
TI Matching Visual Saliency to Confidence in Plots of Uncertain Data
A1 Lester Kwock,
A1 Russell Taylor,
A1 Yueh Lee,
A1 David Feng,
K1 Uncertainty visualization
K1 brushing
K1 scatter plots
K1 parallel coordinates
K1 multivariate data
AB Conveying data uncertainty in visualizations is crucial for preventing viewers from drawing conclusions based on untrustworthy data points. This paper proposes a methodology for efficiently generating density plots of uncertain multivariate data sets that draws viewers to preattentively identify values of high certainty while not calling attention to uncertain values. We demonstrate how to augment scatter plots and parallel coordinates plots to incorporate statistically modeled uncertainty and show how to integrate them with existing multivariate analysis techniques, including outlier detection and interactive brushing. Computing high quality density plots can be expensive for large data sets, so we also describe a probabilistic plotting technique that summarizes the data without requiring explicit density plot computation. These techniques have been useful for identifying brain tumors in multivariate magnetic resonance spectroscopy data and we describe how to extend them to visualize ensemble data sets.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.176
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.176

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 990
TI Perceptual Guidelines for Creating Rectangular Treemaps
A1 Jeffrey Heer,
A1 Nicholas Kong,
A1 Maneesh Agrawala,
K1 Graphical Perception
K1 Visualization
K1 Treemaps
K1 Rectangular Area
K1 Visual Encoding
K1 Experiment
K1 Mechanical Turk
AB Treemaps are space-filling visualizations that make efficient use of limited display space to depict large amounts of hierarchical data. Creating perceptually effective treemaps requires carefully managing a number of design parameters including the aspect ratio and luminance of rectangles. Moreover, treemaps encode values using area, which has been found to be less accurate than judgments of other visual encodings, such as length. We conduct a series of controlled experiments aimed at producing a set of design guidelines for creating effective rectangular treemaps. We find no evidence that luminance affects area judgments, but observe that aspect ratio does have an effect. Specifically, we find that the accuracy of area comparisons suffers when the compared rectangles have extreme aspect ratios or when both are squares. Contrary to common assumptions, the optimal distribution of rectangle aspect ratios within a treemap should include non-squares, but should avoid extremes. We then compare treemaps with hierarchical bar chart displays to identify the data densities at which length-encoded bar charts become less effective than area-encoded treemaps. We report the transition points at which treemaps exhibit judgment accuracy on par with bar charts for both leaf and non-leaf tree nodes. We also find that even at relatively low data densities treemaps result in faster comparisons than bar charts. Based on these results, we present a set of guidelines for the effective use of treemaps and suggest alternate approaches for treemap layout.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.186
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.186

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 999
TI Mental Models, Visual Reasoning and Interaction in Information Visualization: A Top-down Perspective
A1 John Stasko,
A1 Zhicheng Liu,
K1 mental model
K1 model-based reasoning
K1 distributed cognition
K1 interaction
K1 theory
K1 information visualization
AB Although previous research has suggested that examining the interplay between internal and external representations can benefit our understanding of the role of information visualization (InfoVis) in human cognitive activities, there has been little work detailing the nature of internal representations, the relationship between internal and external representations and how interaction is related to these representations. In this paper, we identify and illustrate a specific kind of internal representation, mental models, and outline the high-level relationships between mental models and external visualizations. We present a top-down perspective of reasoning as model construction and simulation, and discuss the role of visualization in model based reasoning. From this perspective, interaction can be understood as active modeling for three primary purposes: external anchoring, information foraging, and cognitive offloading. Finally we discuss the implications of our approach for design, evaluation and theory development
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.177
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.177

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1009
TI Laws of Attraction: From Perceptual Forces to Conceptual Similarity
A1 Caroline Ziemkiewicz,
A1 Robert Kosara,
K1 Perceptual cognition
K1 visualization models
K1 laboratory studies
K1 cognition theory
AB Many of the pressing questions in information visualization deal with how exactly a user reads a collection of visual marks as information about relationships between entities. Previous research has suggested that people see parts of a visualization as objects, and may metaphorically interpret apparent physical relationships between these objects as suggestive of data relationships. We explored this hypothesis in detail in a series of user experiments. Inspired by the concept of implied dynamics in psychology, we first studied whether perceived gravity acting on a mark in a scatterplot can lead to errors in a participant's recall of the mark's position. The results of this study suggested that such position errors exist, but may be more strongly influenced by attraction between marks. We hypothesized that such apparent attraction may be influenced by elements used to suggest relationship between objects, such as connecting lines, grouping elements, and visual similarity. We further studied what visual elements are most likely to cause this attraction effect, and whether the elements that best predicted attraction errors were also those which suggested conceptual relationships most strongly. Our findings show a correlation between attraction errors and intuitions about relatedness, pointing towards a possible mechanism by which the perception of visual marks becomes an interpretation of data relationships.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.174
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.174

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1017
TI Pargnostics: Screen-Space Metrics for Parallel Coordinates
A1 Aritra Dasgupta,
A1 Robert Kosara,
K1 Parallel Coordinates
K1 metrics
K1 display optimization
K1 visualization models.
AB Interactive visualization requires the translation of data into a screen space of limited resolution. While currently ignored by most visualization models, this translation entails a loss of information and the introduction of a number of artifacts that can be useful, (e.g., aggregation, structures) or distracting (e.g., over-plotting, clutter) for the analysis. This phenomenon is observed in parallel coordinates, where overlapping lines between adjacent axes form distinct patterns, representing the relation between variables they connect. However, even for a small number of dimensions, the challenge is to effectively convey the relationships for all combinations of dimensions. The size of the dataset and a large number of dimensions only add to the complexity of this problem. To address these issues, we propose Pargnostics, parallel coordinates diagnostics, a model based on screen-space metrics that quantify the different visual structures. Pargnostics metrics are calculated for pairs of axes and take into account the resolution of the display as well as potential axis inversions. Metrics include the number of line crossings, crossing angles, convergence, overplotting, etc. To construct a visualization view, the user can pick from a ranked display showing pairs of coordinate axes and the structures between them, or examine all possible combinations of axes at once in a matrix display. Picking the best axes layout is an NP-complete problem in general, but we provide a way of automatically optimizing the display according to the user’s preferences based on our metrics and model.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.184
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.184

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1027
TI Comparative Analysis of Multidimensional, Quantitative Data
A1 Karl Kashofer,
A1 C Partl,
A1 M Streit,
A1 A Lex,
A1 Dieter Schmalstieg,
K1 statistical analysis
K1 data analysis
K1 data visualisation
K1 pattern clustering
K1 multidimensional data
K1 comparative analysis
K1 multidimensional quantitative data
K1 biology
K1 physics
K1 engineering
K1 statistical method
K1 clustering algorithm
K1 heat maps
K1 Matchmaker
K1 visualization technique
K1 interactive drill-downs
K1 visual clutter
K1 liver disease
K1 Data visualization
K1 Clustering algorithms
K1 Image color analysis
K1 Heating
K1 Biological cells
K1 Joining processes
K1 bioinformatics visualization.
K1 multidimensional data
K1 cluster comparison
AB When analyzing multidimensional, quantitative data, the comparison of two or more groups of dimensions is a common task. Typical sources of such data are experiments in biology, physics or engineering, which are conducted in different configurations and use replicates to ensure statistically significant results. One common way to analyze this data is to filter it using statistical methods and then run clustering algorithms to group similar values. The clustering results can be visualized using heat maps, which show differences between groups as changes in color. However, in cases where groups of dimensions have an a priori meaning, it is not desirable to cluster all dimensions combined, since a clustering algorithm can fragment continuous blocks of records. Furthermore, identifying relevant elements in heat maps becomes more difficult as the number of dimensions increases. To aid in such situations, we have developed Matchmaker, a visualization technique that allows researchers to arbitrarily arrange and compare multiple groups of dimensions at the same time. We create separate groups of dimensions which can be clustered individually, and place them in an arrangement of heat maps reminiscent of parallel coordinates. To identify relations, we render bundled curves and ribbons between related records in different groups. We then allow interactive drill-downs using enlarged detail views of the data, which enable in-depth comparisons of clusters between groups. To reduce visual clutter, we minimize crossings between the views. This paper concludes with two case studies. The first demonstrates the value of our technique for the comparison of clustering algorithms. In the second, biologists use our system to investigate why certain strains of mice develop liver disease while others remain healthy, informally showing the efficacy of our system when analyzing multidimensional data containing distinct groups of dimensions.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.138
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.138

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1036
TI An Extension of Wilkinson’s Algorithm for Positioning Tick Labels on Axes
A1 Pat Hanrahan,
A1 Justin Talbot,
A1 Sharon Lin,
K1 axis labeling
K1 nice numbers
AB The non-data components of a visualization, such as axes and legends, can often be just as important as the data itself. They provide contextual information essential to interpreting the data. In this paper, we describe an automated system for choosing positions and labels for axis tick marks. Our system extends Wilkinson’s optimization-based labeling approach to create a more robust, full-featured axis labeler. We define an expanded space of axis labelings by automatically generating additional nice numbers as needed and by permitting the extreme labels to occur inside the data range. These changes provide flexibility in problematic cases, without degrading quality elsewhere. We also propose an additional optimization criterion, legibility, which allows us to simultaneously optimize over label formatting, font size, and orientation. To solve this revised optimization problem, we describe the optimization function and an efficient search algorithm. Finally, we compare our method to previous work using both quantitative and qualitative metrics. This paper is a good example of how ideas from automated graphic design can be applied to information visualization.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.130
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.130

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1044
TI Stacking Graphic Elements to Avoid Over-Plotting
A1 Anushka Anand,
A1 Tuan Nhon Dang,
A1 Leland Wilkinson,
K1 dot plots
K1 Parallel coordinate plots
K1 Multidimensional data
K1 Density-based visualization
AB An ongoing challenge for information visualization is how to deal with over-plotting forced by ties or the relatively limitedvisual field of display devices. A popular solution is to represent local data density with area (bubble plots, treemaps), color(heatmaps), or aggregation (histograms, kernel densities, pixel displays). All of these methods have at least one of three deficiencies:1) magnitude judgments are biased because area and color have convex downward perceptual functions, 2) area, hue, and brightnesshave relatively restricted ranges of perceptual intensity compared to length representations, and/or 3) it is difficult to brush or link toindividual cases when viewing aggregations. In this paper, we introduce a new technique for visualizing and interacting with datasetsthat preserves density information by stacking overlapping cases. The overlapping data can be points or lines or other geometricelements, depending on the type of plot. We show real-dataset applications of this stacking paradigm and compare them to othertechniques that deal with over-plotting in high-dimensional displays.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.197
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.197

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1053
TI Visualization of Diversity in Large Multivariate Data Sets
A1 Tuan Pham,
A1 Crystal Ju,
A1 Rob Hess,
A1 Eugene Zhang,
A1 Ronald Metoyer,
K1 information visualization
K1 diversity
K1 categorical data
K1 multivariate data
K1 evaluation
AB Understanding the diversity of a set of multivariate objects is an important problem in many domains, including ecology, college admissions, investing, machine learning, and others. However, to date, very little work has been done to help users achieve this kind of understanding. Visual representation is especially appealing for this task because it offers the potential to allow users to efficiently observe the objects of interest in a direct and holistic way. Thus, in this paper, we attempt to formalize the problem of visualizing the diversity of a large (more than 1000 objects), multivariate (more than 5 attributes) data set as one worth deeper investigation by the information visualization community. In doing so, we contribute a precise definition of diversity, a set of requirements for diversity visualizations based on this definition, and a formal user study design intended to evaluate the capacity of a visual representation for communicating diversity information. Our primary contribution, however, is a visual representation, called the Diversity Map, for visualizing diversity. An evaluation of the Diversity Map using our study design shows that users can judge elements of diversity consistently and as or more accurately than when using the only other representation specifically designed to visualize diversity.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.216
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.216

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1063
TI PedVis: A Structured, Space-Efficient Technique for Pedigree Visualization
A1 Claurissa Tuttle,
A1 Claudio Silva,
A1 Luis Gustavo Nonato,
K1 Genealogy
K1 Pedigree
K1 H-Tree
AB Public genealogical databases are becoming increasingly populated with historical data and records of the current population's ancestors. As this increasing amount of available information is used to link individuals to their ancestors, the resulting trees become deeper and more dense, which justifies the need for using organized, space-efficient layouts to display the data. Existing layouts are often only able to show a small subset of the data at a time. As a result, it is easy to become lost when navigating through the data or to lose sight of the overall tree structure. On the contrary, leaving space for unknown ancestors allows one to better understand the tree's structure, but leaving this space becomes expensive and allows fewer generations to be displayed at a time. In this work, we propose that the H-tree based layout be used in genealogical software to display ancestral trees. We will show that this layout presents an increase in the number of displayable generations, provides a nicely arranged, symmetrical, intuitive and organized fractal structure, increases the user's ability to understand and navigate through the data, and accounts for the visualization requirements necessary for displaying such trees. Finally, user-study results indicate potential for user acceptance of the new layout.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.185
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.185

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1073
TI GeneaQuilts: A System for Exploring Large Genealogies
A1 Juhee Bae,
A1 Anastasia Bezerianos,
A1 Jean-Daniel Fekete,
A1 Ben Watson,
A1 Pierre Dragicevic,
K1 genealogy visualization
K1 interaction
AB GeneaQuilts is a new visualization technique for representing large genealogies of up to several thousand individuals. Thevisualization takes the form of a diagonally-filled matrix, where rows are individuals and columns are nuclear families. After identifyingthe major tasks performed in genealogical research and the limits of current software, we present an interactive genealogy explorationsystem based on GeneaQuilts. The system includes an overview, a timeline, search and filtering components, and a new interactiontechnique called Bring & Slide that allows fluid navigation in very large genealogies. We report on preliminary feedback from domain experts and show how our system supports a number of their tasks.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.159
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.159

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1082
TI Visualization of Graph Products
A1 Marc Hellmuth,
A1 Stefan Jänicke,
A1 Peter F. Stadler,
A1 Gerik Scheuermann,
A1 Christian Heine,
K1 Graph drawing
K1 graph products
K1 TopoLayout.
AB Graphs are a versatile structure and abstraction for binary relationships between objects. To gain insight into such relationships, their corresponding graph can be visualized. In the past, many classes of graphs have been defined, e.g. trees, planar graphs, directed acyclic graphs, and visualization algorithms were proposed for these classes. Although many graphs may only be classified as "general" graphs, they can contain substructures that belong to a certain class. Archambault proposed the TopoLayout framework: rather than draw any arbitrary graph using one method, split the graph into components that are homogeneous with respect to one graph class and then draw each component with an algorithm best suited for this class. Graph products constitute a class that arises frequently in graph theory, but for which no visualization algorithm has been proposed until now. In this paper, we present an algorithm for drawing graph products and the aesthetic criterion graph product's drawings are subject to. We show that the popular High-Dimensional Embedder approach applied to cartesian products already respects this aestetic criterion, but has disadvantages. We also present how our method is integrated as a new component into the TopoLayout framework. Our implementation is used for further research of graph products in a biological context.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.217
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.217

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1090
TI Untangling Euler Diagrams
A1 Tim Dwyer,
A1 Nathalie Henry Riche,
K1 Information Visualization
K1 Euler diagrams
K1 Set Visualization
K1 Graph Visualization.
AB In many common data analysis scenarios the data elements are logically grouped into sets. Venn and Euler style diagrams are a common visual representation of such set membership where the data elements are represented by labels or glyphs and sets are indicated by boundaries surrounding their members. Generating such diagrams automatically such that set regions do not intersect unless the corresponding sets have a non-empty intersection is a difficult problem. Further, it may be impossible in some cases if regions are required to be continuous and convex. Several approaches exist to draw such set regions using more complex shapes, however, the resulting diagrams can be difficult to interpret. In this paper we present two novel approaches for simplifying a complex collection of intersecting sets into a strict hierarchy that can be more easily automatically arranged and drawn (Figure 1). In the first approach, we use compact rectangular shapes for drawing each set, attempting to improve the readability of the set intersections. In the second approach, we avoid drawing intersecting set regions by duplicating elements belonging to multiple sets. We compared both of our techniques to the traditional non-convex region technique using five readability tasks. Our results show that the compact rectangular shapes technique was often preferred by experimental subjects even though the use of duplications dramatically improves the accuracy and performance time for most of our tasks. In addition to general set representation our techniques are also applicable to visualization of networks with intersecting clusters of nodes
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.210
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.210

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1100
TI The FlowVizMenu and Parallel Scatterplot Matrix: Hybrid Multidimensional Visualizations for Network Exploration
A1 Christophe Viau,
A1 Michael J. McGuffin,
A1 Igor Jurisica,
A1 Yves Chiricota,
K1 interactive graph drawing
K1 network layout
K1 attribute-driven layout
K1 parallel coordinates
K1 scatterplot matrix
K1 radial menu
AB A standard approach for visualizing multivariate networks is to use one or more multidimensional views (for example, scatterplots) for selecting nodes by various metrics, possibly coordinated with a node-link view of the network. In this paper, we present three novel approaches for achieving a tighter integration of these views through hybrid techniques for multidimensional visualization, graph selection and layout. First, we present the FlowVizMenu, a radial menu containing a scatterplot that can be popped up transiently and manipulated with rapid, fluid gestures to select and modify the axes of its scatterplot. Second, the FlowVizMenu can be used to steer an attribute-driven layout of the network, causing certain nodes of a node-link diagram to move toward their corresponding positions in a scatterplot while others can be positioned manually or by force-directed layout. Third, we describe a novel hybrid approach that combines a scatterplot matrix (SPLOM) and parallel coordinates called the Parallel Scatterplot Matrix (P-SPLOM), which can be used to visualize and select features within the network. We also describe a novel arrangement of scatterplots called the Scatterplot Staircase (SPLOS) that requires less space than a traditional scatterplot matrix. Initial user feedback is reported.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.205
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.205

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1109
TI OpinionSeer: Interactive Visualization of Hotel Customer Feedback
A1 Weiwei Cui,
A1 Huamin Qu,
A1 Yingcai Wu,
A1 Norman Au,
A1 Hong Zhou,
A1 Shixia Liu,
A1 Furu Wei,
K1 opinion visualization
K1 radial visualization
K1 uncertainty visualization
AB The rapid development of Web technology has resulted in an increasing number of hotel customers sharing their opinionson the hotel services. Effective visual analysis of online customer opinions is needed, as it has a significant impact on buildinga successful business. In this paper, we present OpinionSeer, an interactive visualization system that could visually analyze alarge collection of online hotel customer reviews. The system is built on a new visualization-centric opinion mining technique thatconsiders uncertainty for faithfully modeling and analyzing customer opinions. A new visual representation is developed to conveycustomer opinions by augmenting well-established scatterplots and radial visualization. To provide multiple-level exploration, weintroduce subjective logic to handle and organize subjective opinions with degrees of uncertainty. Several case studies illustrate theeffectiveness and usefulness of OpinionSeer on analyzing relationships among multiple data dimensions and comparing opinionsof different groups. Aside from data on hotel customer feedback, OpinionSeer could also be applied to visually analyze customeropinions on other products or services.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.183
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.183

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1119
TI The Streams of Our Lives: Visualizing Listening Histories in Context
A1 Frederik Seiffert,
A1 Michael Sedlmair,
A1 Sebastian Boring,
A1 Dominikus Baur,
K1 Information visualization
K1 lifelogging
K1 design study
K1 music
K1 listening history
K1 timelines
K1 photos
K1 calendars
AB The choices we take when listening to music are expressions of our personal taste and character. Storing and accessing our listening histories is trivial due to services like Last.fm, but learning from them and understanding them is not. Existing solutions operate at a very abstract level and only produce statistics. By applying techniques from information visualization to this problem, we were able to provide average people with a detailed and powerful tool for accessing their own musical past. LastHistory is an interactive visualization for displaying music listening histories, along with contextual information from personal photos and calendar entries. Its two main user tasks are (1) analysis, with an emphasis on temporal patterns and hypotheses related to musical genre and sequences, and (2) reminiscing, where listening histories and context represent part of one's past. In this design study paper we give an overview of the field of music listening histories and explain their unique characteristics as a type of personal data. We then describe the design rationale, data and view transformations of LastHistory and present the results from both a lab- and a large-scale online study. We also put listening histories in contrast to other lifelogging data. The resonant and enthusiastic feedback that we received from average users shows a need for making their personal data accessible. We hope to stimulate such developments through this research.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.206
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.206

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1129
TI A Visual Backchannel for Large-Scale Events
A1 Sheelagh Carpendale,
A1 Daniel Gruen,
A1 Carey Williamson,
A1 Marian Dörk,
K1 backchannel
K1 information visualization
K1 events
K1 multiple views
K1 microblogging
K1 information retrieval
K1 World Wide Web
AB We introduce the concept of a Visual Backchannel as a novel way of following and exploring online conversations aboutlarge-scale events. Microblogging communities, such as Twitter, are increasingly used as digital backchannels for timely exchange ofbrief comments and impressions during political speeches, sport competitions, natural disasters, and other large events. Currently,shared updates are typically displayed in the form of a simple list, making it difficult to get an overview of the fast-paced discussions asit happens in the moment and how it evolves over time. In contrast, our Visual Backchannel design provides an evolving, interactive,and multi-faceted visual overview of large-scale ongoing conversations on Twitter. To visualize a continuously updating informationstream, we include visual saliency for what is happening now and what has just happened, set in the context of the evolving conversation.As part of a fully web-based coordinated-view system we introduce Topic Streams, a temporally adjustable stacked graphvisualizing topics over time, a People Spiral representing participants and their activity, and an Image Cloud encoding the popularityof event photos by size. Together with a post listing, these mutually linked views support cross-filtering along topics, participants, andtime ranges. We discuss our design considerations, in particular with respect to evolving visualizations of dynamically changing data.Initial feedback indicates significant interest and suggests several unanticipated uses.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.129
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.129

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1139
TI Narrative Visualization: Telling Stories with Data
A1 Jeffrey Heer,
A1 Edward Segel,
K1 Narrative visualization
K1 storytelling
K1 design methods
K1 case study
K1 journalism
K1 social data analysis
AB Data visualization is regularly promoted for its ability to reveal stories within data, yet these “data stories” differ in important ways from traditional forms of storytelling. Storytellers, especially online journalists, have increasingly been integrating visualizations into their narratives, in some cases allowing the visualization to function in place of a written story. In this paper, we systematically review the design space of this emerging class of visualizations. Drawing on case studies from news media to visualization research, we identify distinct genres of narrative visualization. We characterize these design differences, together with interactivity and messaging, in terms of the balance between the narrative flow intended by the author (imposed by graphical elements and the interface) and story discovery on the part of the reader (often through interactive exploration). Our framework suggests design strategies for narrative visualization, including promising under-explored approaches to journalistic storytelling and educational media.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.179
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.179

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1149
TI Declarative Language Design for Interactive Visualization
A1 Jeffrey Heer,
A1 Michael Bostock,
K1 information visualization
K1 user interfaces
K1 toolkits
K1 domain specific languages
K1 declarative languages
K1 optimization
AB We investigate the design of declarative, domain-specific languages for constructing interactive visualizations. By separatingspecification from execution, declarative languages can simplify development, enable unobtrusive optimization, and supportretargeting across platforms. We describe the design of the Protovis specification language and its implementation within anobject-oriented, statically-typed programming language (Java). We demonstrate how to support rich visualizations without requiring atoolkit-specific data model and extend Protovis to enable declarative specification of animated transitions. To support cross-platformdeployment, we introduce rendering and event-handling infrastructures decoupled from the runtime platform, letting designers retargetvisualization specifications (e.g., from desktop to mobile phone) with reduced effort. We also explore optimizations such as runtimecompilation of visualization specifications, parallelized execution, and hardware-accelerated rendering. We present benchmark studiesmeasuring the performance gains provided by these optimizations and compare performance to existing Java-based visualizationtools, demonstrating scalability improvements exceeding an order of magnitude.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.144
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.144

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1157
TI Visualizations Everywhere: A Multiplatform Infrastructure for Linked Visualizations
A1 Steven Drucker,
A1 Roland Fernandez,
A1 Danyel Fisher,
A1 Scott Ruble,
K1 Visualization systems
K1 toolkit design
K1 data transformation and representation
AB In order to use new visualizations, most toolkits require application developers to rebuild their applications and distribute new versions to users. The WebCharts Framework take a different approach by hosting JavaScript from within an application and providing a standard data and events interchange. In this way, applications can be extended dynamically, with a wide variety of visualizations. We discuss the benefits of this architectural approach, contrast it to existing techniques, and give a variety of examples and extensions of the basic system.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.222
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.222

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1172
TI FacetAtlas: Multifaceted Visualization for Rich Text Corpora
A1 Yu-Ru Lin,
A1 Shixia Liu,
A1 Jimeng Sun,
A1 Huamin Qu,
A1 David Gotz,
A1 Nan Cao,
K1 Multifaceted visualization
K1 Text visualization
K1 Multi-relational Graph
K1 Search UI
AB Documents in rich text corpora usually contain multiple facets of information. For example, an article about a specific disease often consists of different facets such as symptom, treatment, cause, diagnosis, prognosis, and prevention. Thus, documents may have different relations based on different facets. Powerful search tools have been developed to help users locate lists of individual documents that are most related to specific keywords. However, there is a lack of effective analysis tools that reveal the multifaceted relations of documents within or cross the document clusters. In this paper, we present FacetAtlas, a multifaceted visualization technique for visually analyzing rich text corpora. FacetAtlas combines search technology with advanced visual analytical tools to convey both global and local patterns simultaneously. We describe several unique aspects of FacetAtlas, including (1) node cliques and multifaceted edges, (2) an optimized density map, and (3) automated opacity pattern enhancement for highlighting visual patterns, (4) interactive context switch between facets. In addition, we demonstrate the power of FacetAtlas through a case study that targets patient education in the health care domain. Our evaluation shows the benefits of this work, especially in support of complex multifaceted data analysis.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.154
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.154

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1182
TI SparkClouds: Visualizing Trends in Tag Clouds
A1 Sheelash Carpendale,
A1 Amy K. Karlson,
A1 Bongshin Lee,
A1 Nathalie Henry Riche,
K1 Tag clouds
K1 trend visualization
K1 multiple line graphs
K1 stacked bar charts
K1 evaluation
AB Tag clouds have proliferated over the web over the last decade. They provide a visual summary of a collection of texts by visually depicting the tag frequency by font size. In use, tag clouds can evolve as the associated data source changes over time. Interesting discussions around tag clouds often include a series of tag clouds and consider how they evolve over time. However, since tag clouds do not explicitly represent trends or support comparisons, the cognitive demands placed on the person for perceiving trends in multiple tag clouds are high. In this paper, we introduce SparkClouds, which integrate sparklines [23] into a tag cloud to convey trends between multiple tag clouds. We present results from a controlled study that compares SparkClouds with two traditional trend visualizations—multiple line graphs and stacked bar charts—as well as Parallel Tag Clouds [4]. Results show that SparkClouds ability to show trends compares favourably to the alternative visualizations.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.194
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.194

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1190
TI ManiWordle: Providing Flexible Control over Wordle
A1 Kyle Koh,
A1 Jinwook Seo,
A1 Bongshin Lee,
A1 Bohyoung Kim,
K1 Interaction design
K1 direct manipulation
K1 flexibilty-usability tradeoff
K1 tag-cloud
K1 participatory visualization
K1 user study.
AB Among the multifarious tag-clouding techniques, Wordle stands out to the community by providing an aesthetic layout, eliciting the emergence of the participatory culture and usage of tag-clouding in the artistic creations. In this paper, we introduce ManiWordle, a Wordle-based visualization tool that revamps interactions with the layout by supporting custom manipulations. ManiWordle allows people to manipulate typography, color, and composition not only for the layout as a whole, but also for the individual words, enabling them to have better control over the layout result. We first describe our design rationale along with the interaction techniques for tweaking the layout. We then present the results both from the preliminary usability study and from the comparative study between ManiWordle and Wordle. The results suggest that ManiWordle provides higher user satisfaction and an efficient method of creating the desired "art work," harnessing the power behind the ever-increasing popularity of Wordle.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.175
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.175

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1198
TI On the Fractal Dimension of Isosurfaces
A1 Marc Khoury,
A1 Rephael Wenger,
K1 Isosurfaces
K1 scalar data
K1 fractal dimension
AB A (3D) scalar grid is a regular $n_1 x n_2 x n_3$ grid of vertices where each vertex v is associated with some scalar value $s_v$. ;Applying trilinear interpolation, the scalar grid determines a scalar function g where $g(v) = s_v$ for each grid vertex v. An isosurface with ;isovalue s is a triangular mesh which approximates the level set $g^{-1}(α)$. The fractal dimension of an isosurface represents the growth ;in the isosurface as the number of grid cubes increases. We dene and discuss the fractal isosurface dimension. Plotting the fractal ;dimension as a function of the isovalues in a data set provides information about the isosurfaces determined by the data set. We present statistics on the average fractal dimension of 60 publicly available benchmark data sets. We also show the fractal dimension is highly correlated with topological noise in the benchmark data sets, measuring the topological noise by the number of connected components in the isosurface. Lastly, we present a formula predicting the fractal dimension as a function of noise and validate the formula with experimental results.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.182
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.182

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1206
TI An Information-theoretic Framework for Visualization
A1 Heike Jaenicke,
A1 Min Chen,
K1 Information theory
K1 theory of visualization
K1 quantitative evaluation
AB In this paper, we examine whether or not information theory can be one of the theoretic frameworks for visualization. We formulate concepts and measurements for qualifying visual information. We illustrate these concepts with examples that manifest the intrinsic and implicit use of information theory in many existing visualization techniques. We outline the broad correlation between visualization and the major applications of information theory, while pointing out the difference in emphasis and some technical gaps. Our study provides compelling evidence that information theory can explain a significant number of phenomena or events in visualization, while no example has been found which is fundamentally in conflict with information theory. We also notice that the emphasis of some traditional applications of information theory, such as data compression or data communication, may not always suit visualization, as the former typically focuses on the efficient throughput of a communication channel, whilst the latter focuses on the effectiveness in aiding the perceptual and cognitive process for data understanding and knowledge discovery. These findings suggest that further theoretic developments are necessary for adopting and adapting information theory for visualization.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.132
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.132

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1216
TI An Information-Theoretic Framework for Flow Visualization
A1 Teng-Yok Lee,
A1 Lijie Xu,
A1 Han-Wei Shen,
K1 Flow field visualization
K1 information theory
K1 streamline generation.
AB The process of visualization can be seen as a visual communication channel where the input to the channel is the raw data, and the output is the result of a visualization algorithm. From this point of view, we can evaluate the effectiveness of visualization by measuring how much information in the original data is being communicated through the visual communication channel. In this paper, we present an information-theoretic framework for flow visualization with a special focus on streamline generation. In our framework, a vector field is modeled as a distribution of directions from which Shannon's entropy is used to measure the information content in the field. The effectiveness of the streamlines displayed in visualization can be measured by first constructing a new distribution of vectors derived from the existing streamlines, and then comparing this distribution with that of the original data set using the conditional entropy. The conditional entropy between these two distributions indicates how much information in the original data remains hidden after the selected streamlines are displayed. The quality of the visualization can be improved by progressively introducing new streamlines until the conditional entropy converges to a small value. We describe the key components of our framework with detailed analysis, and show that the framework can effectively visualize 2D and 3D flow data.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.131
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.131

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1225
TI Streak Lines as Tangent Curves of a Derived Vector Field
A1 Tino Weinkauf,
A1 Holger Theisel,
K1 unsteady flow visualization
K1 streak lines
K1 streak surfaces
K1 feature extraction
AB Characteristic curves of vector fields include stream, path, and streak lines. Stream and path lines can be obtained by a simple vector field integration of an autonomous ODE system, i.e., they can be described as tangent curves of a vector field. This facilitates their mathematical analysis including the extraction of core lines around which stream or path lines exhibit swirling motion, or the computation of their curvature for every point in the domain without actually integrating them. Such a description of streak lines is not yet available, which excludes them from most of the feature extraction and analysis tools that have been developed in our community. In this paper, we develop the first description of streak lines as tangent curves of a derived vector field - the streak line vector field - and show how it can be computed from the spatial and temporal gradients of the flow map, i.e., a dense path line integration is required. We demonstrate the high accuracy of our approach by comparing it to solutions where the ground truth is analytically known and to solutions where the ground truth has been obtained using the classic streak line computation. Furthermore, we apply a number of feature extraction and analysis tools to the new streak line vector field including the extraction of cores of swirling streak lines and the computation of streak line curvature fields. These first applications foreshadow the large variety of possible future research directions based on our new mathematical description of streak lines.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.198
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.198

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1235
TI A Curved Ray Camera for Handling Occlusions through Continuous Multiperspective Visualization
A1 Voicu Popescu,
A1 Jian Cui,
A1 Christoph Hoffmann,
A1 Paul Rosen,
K1 Alleviating occlusions
K1 camera model
K1 curved rays
K1 multiperspective visualization
K1 interactive visualization
AB Most images used in visualization are computed with the planar pinhole camera. This classic camera model has important advantages such as simplicity, which enables efficient software and hardware implementations, and similarity to the human eye, which yields images familiar to the user. However, the planar pinhole camera has only a single viewpoint, which limits images to parts of the scene to which there is direct line of sight. In this paper we introduce the curved ray camera to address the single viewpoint limitation. Rays are C1-continuous curves that bend to circumvent occluders. Our camera is designed to provide a fast 3-D point projection operation, which enables interactive visualization. The camera supports both 3-D surface and volume datasets. The camera is a powerful tool that enables seamless integration of multiple perspectives for overcoming occlusions in visualization while minimizing distortions.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.127
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.127

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1243
TI Special Relativistic Visualization by Local Ray Tracing
A1 Daniel Weiskopf,
A1 Sebastian Grottel,
A1 Thomas Müller,
K1 Poincare transformation
K1 aberration of light
K1 Doppler effect
K1 illumination
K1 searchlight effect
K1 special relativity
K1 GPU ray tracing
AB Special relativistic visualization offers the possibility of experiencing the optical effects of traveling near the speed of light, including apparent geometric distortions as well as Doppler and searchlight effects. Early high-quality computer graphics images of relativistic scenes were created using offline, computationally expensive CPU-side 4D ray tracing. Alternate approaches such as image-based rendering and polygon-distortion methods are able to achieve interactivity, but exhibit inferior visual quality due to sampling artifacts. In this paper, we introduce a hybrid rendering technique based on polygon distortion and local ray tracing that facilitates interactive high-quality visualization of multiple objects moving at relativistic speeds in arbitrary directions. The method starts by calculating tight image-space footprints for the apparent triangles of the 3D scene objects. The final image is generated using a single image-space ray tracing step incorporating Doppler and searchlight effects. Our implementation uses GPU shader programming and hardware texture filtering to achieve high rendering speed.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.196
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.196

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1251
TI Computing Robustness and Persistence for Images
A1 Paul Bendich,
A1 Michael Kerber,
A1 Herbert Edelsbrunner,
K1 voxel arrays
K1 oct-trees
K1 persistent homology
K1 persistence diagrams
K1 level sets
K1 robustness
K1 approximations
K1 plant roots
AB We are interested in 3-dimensional images given as arrays of voxels with intensity values. Extending these values to acontinuous function, we study the robustness of homology classes in its level and interlevel sets, that is, the amount of perturbationneeded to destroy these classes. The structure of the homology classes and their robustness, over all level and interlevel sets, can bevisualized by a triangular diagram of dots obtained by computing the extended persistence of the function. We give a fast hierarchicalalgorithm using the dual complexes of oct-tree approximations of the function. In addition, we show that for balanced oct-trees, thedual complexes are geometrically realized in $R^3$ and can thus be used to construct level and interlevel sets. We apply these tools tostudy 3-dimensional images of plant root systems.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.139
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.139

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1261
TI Browsing Large Image Datasets through Voronoi Diagrams
A1 Paolo Cignoni,
A1 Marco Tarini,
A1 Paolo Brivio,
K1 visualization System and Toolkit Design
K1 Scalability Issues
K1 User Interfaces
K1 Zooming and Navigation Techniques
AB Conventional browsing of image collections use mechanisms such as thumbnails arranged on a regular grid or on a line,often mounted over a scrollable panel. However, this approach does not scale well with the size of the datasets (number of images).In this paper, we propose a new thumbnail-based interface to browse large collections of images. Our approach is based on weightedcentroidal anisotropic Voronoi diagrams. A dynamically changing subset of images is represented by thumbnails and shown on the screen. Thumbnails are shaped like general polygons, to better cover screen space, while still reflecting the original aspect ratios or orientation of the represented images. During the browsing process, thumbnails are dynamically rearranged, reshaped and rescaled. The objective is to devote more screen space (more numerous and larger thumbnails) to the parts of the dataset closer to the current region of interest, and progressively lesser away from it, while still making the dataset visible as a whole. During the entire process, temporal coherence is always maintained. GPU implementation easily guarantees the frame rates needed for fully smooth interactivity.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.136
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.136

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1271
TI Visual Exploration of High Dimensional Scalar Functions
A1 R Whitaker,
A1 V Pascucci,
A1 P Bremer,
A1 S Gerber,
K1 Crystals
K1 Manifolds
K1 Approximation methods
K1 Data visualization
K1 Kernel
K1 Geometry
K1 Concrete
K1 Morse-Smale complex
K1 Morse theory
K1 High-dimensional visualization
AB An important goal of scientific data analysis is to understand the behavior of a system or process based on a sample of the system. In many instances it is possible to observe both input parameters and system outputs, and characterize the system as a high-dimensional function. Such data sets arise, for instance, in large numerical simulations, as energy landscapes in optimization problems, or in the analysis of image data relating to biological or medical parameters. This paper proposes an approach to analyze and visualizing such data sets. The proposed method combines topological and geometric techniques to provide interactive visualizations of discretely sampled high-dimensional scalar fields. The method relies on a segmentation of the parameter space using an approximate Morse-Smale complex on the cloud of point samples. For each crystal of the Morse-Smale complex, a regression of the system parameters with respect to the output yields a curve in the parameter space. The result is a simplified geometric representation of the Morse-Smale complex in the high dimensional input domain. Finally, the geometric representation is embedded in 2D, using dimension reduction, to provide a visualization platform. The geometric properties of the regression curves enable the visualization of additional information about each crystal such as local and global shape, width, length, and sampling densities. The method is illustrated on several synthetic examples of two dimensional functions. Two use cases, using data sets from the UCI machine learning repository, demonstrate the utility of the proposed approach on real data. Finally, in collaboration with domain experts the proposed method is applied to two scientific challenges. The analysis of parameters of climate simulations and their relationship to predicted global energy flux and the concentrations of chemical species in a combustion simulation and their integration with temperature.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.213
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.213

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1281
TI Two-Phase Mapping for Projecting Massive Data Sets
A1 Claudio T. Silva,
A1 Fernando V. Paulovich,
A1 Luis G. Nonato,
K1 Dimensionality Reduction; Projection Methods; Visual Data Mining; Streaming Technique
AB Most multidimensional projection techniques rely on distance (dissimilarity) information between data instances to embed high-dimensional data into a visual space. When data are endowed with Cartesian coordinates, an extra computational effort is necessary to compute the needed distances, making multidimensional projection prohibitive in applications dealing with interactivity and massive data. The novel multidimensional projection technique proposed in this work, called Part-Linear Multidimensional Projection (PLMP), has been tailored to handle multivariate data represented in Cartesian high-dimensional spaces, requiring only distance information between pairs of representative samples. This characteristic renders PLMP faster than previous methods when processing large data sets while still being competitive in terms of precision. Moreover, knowing the range of variation for data instances in the high-dimensional space, we can make PLMP a truly streaming data projection technique, a trait absent in previous methods.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.207
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.207

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1291
TI Discontinuities in Continuous Scatter Plots
A1 Holger Theisel,
A1 Dirk J. Lehmann,
K1 Discontinuity
K1 Scatterplot
K1 Topology
K1 Data Visualization
AB The concept of continuous scatterplot (CSP) is a modern visualization technique. The idea is to define a scalar density value based on the map between an n-dimensional spatial domain and an m-dimensional data domain, which describe the CSP space. Usually the data domain is two-dimensional to visually convey the underlying, density coded, data. In this paper we investigate kinds of map-based discontinuities, especially for the practical cases n = m = 2 and n = 3 | m = 2, and we depict relations between them and attributes of the resulting CSP itself. Additionally, we show that discontinuities build critical line structures, and we introduce algorithms to detect them. Further, we introduce a discontinuity-based visualization approach—called contribution map (CM)—which establishes a relationship between the CSP's data domain and the number of connected components in the spatial domain. We show that CMs enhance the CSP-based linking & brushing interaction. Finally, we apply our approaches to a number of synthetic as well as real data sets.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.146
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.146

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1301
TI Spatial Conditioning of Transfer Functions Using Local Material Distributions
A1 Claes Lundström,
A1 Anders Persson,
A1 Stefan Lindholm,
A1 Anders Ynnerman,
A1 Patric Ljung,
K1 Direct Volume Rendering
K1 Transfer Function
K1 Spatial Conditioning
K1 Neighborhood Meta-Data.
AB In many applications of Direct Volume Rendering (DVR) the importance of a certain material or feature is highly dependent on its relative spatial location. For instance, in the medical diagnostic procedure, the patient's symptoms often lead to specification of features, tissues and organs of particular interest. One such example is pockets of gas which, if found inside the body at abnormal locations, are a crucial part of a diagnostic visualization. This paper presents an approach that enhances DVR transfer function design with spatial localization based on user specified material dependencies. Semantic expressions are used to define conditions based on relations between different materials, such as only render iodine uptake when close to liver. The underlying methods rely on estimations of material distributions which are acquired by weighing local neighborhoods of the data against approximations of material likelihood functions. This information is encoded and used to influence rendering according to the user's specifications. The result is improved focus on important features by allowing the user to suppress spatially less-important data. In line with requirements from actual clinical DVR practice, the methods do not require explicit material segmentation that would be impossible or prohibitively time-consuming to achieve in most real cases. The scheme scales well to higher dimensions which accounts for multi-dimensional transfer functions and multivariate data. Dual-Energy Computed Tomography, an important new modality in radiology, is used to demonstrate this scalability. In several examples we show significantly improved focus on clinically important aspects in the rendered images.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.195
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.195

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1311
TI Exploded View Diagrams of Mathematical Surfaces
A1 Niloy Mitra,
A1 Maneesh Agrawala,
A1 Olga Karpenko,
A1 Wilmot Li,
K1 exploded view diagrams
K1 mathematical visualization
K1 symmetry
AB We present a technique for visualizing complicated mathematical surfaces that is inspired by hand-designed topological illustrations. Our approach generates exploded views that expose the internal structure of such a surface by partitioning it into parallel slices, which are separated from each other along a single linear explosion axis. Our contributions include a set of simple, prescriptive design rules for choosing an explosion axis and placing cutting planes, as well as automatic algorithms for applying these rules. First we analyze the input shape to select the explosion axis based on the detected rotational and reflective symmetries of the input model. We then partition the shape into slices that are designed to help viewers better understand how the shape of the surface and its cross-sections vary along the explosion axis. Our algorithms work directly on triangle meshes, and do not depend on any specific parameterization of the surface. We generate exploded views for a variety of mathematical surfaces using our system.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.151
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.151

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1319
TI IRIS: Illustrative Rendering for Integral Surfaces
A1 Bernd Hamann,
A1 Mathias Hummel,
A1 Christoph Garth,
A1 Kenneth I. Joy,
A1 Hans Hagen,
K1 flow visualization
K1 integral surfaces
K1 illustrative rendering
AB Integral surfaces are ideal tools to illustrate vector fields and fluid flow structures. However, these surfaces can be visually complex and exhibit difficult geometric properties, owing to strong stretching, shearing and folding of the flow from which they are derived. Many techniques for non-photorealistic rendering have been presented previously. It is, however, unclear how these techniques can be applied to integral surfaces. In this paper, we examine how transparency and texturing techniques can be used with integral surfaces to convey both shape and directional information. We present a rendering pipeline that combines these techniques aimed at faithfully and accurately representing integral surfaces while improving visualization insight. The presented pipeline is implemented directly on the GPU, providing real-time interaction for all rendering modes, and does not require expensive preprocessing of integral surfaces after computation.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.173
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.173

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1329
TI Illustrative Stream Surfaces
A1 Silvia Born,
A1 Alexander Wiebel,
A1 Dirk Bartz,
A1 Gerik Scheuermann,
A1 Jan Friedrich,
K1 flow visualization
K1 stream surfaces
K1 illustrative rendering
K1 silhouettes
K1 GPU technique
K1 3D vector fields
AB Stream surfaces are an intuitive approach to represent 3D vector fields. In many cases, however, they are challenging objects to visualize and to understand, due to a high degree of self-occlusion. Despite the need for adequate rendering methods, little work has been done so far in this important research area. In this paper, we present an illustrative rendering strategy for stream surfaces. In our approach, we apply various rendering techniques, which are inspired by the traditional flow illustrations drawn by Dallmann and Abraham \& Shaw in the early 1980s. Among these techniques are contour lines and halftoning to show the overall surface shape. Flow direction as well as singularities on the stream surface are depicted by illustrative surface streamlines. ;To go beyond reproducing static text book images, we provide several interaction features, such as movable cuts and slabs allowing an interactive exploration of the flow and insights into subjacent structures, e.g., the inner windings of vortex breakdown bubbles. These methods take only the parameterized stream surface as input, require no further preprocessing, and can be freely combined by the user. We explain the design, GPU-implementation, and combination of the different illustrative rendering and interaction methods and demonstrate the potential of our approach by applying it to stream surfaces from various flow simulations. ;
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.166
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.166

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1339
TI Exploration of 4D MRI Blood Flow using Stylistic Visualization
A1 Marcel Breeuwer,
A1 Bart ter Haar Romenij,
A1 M. Eduard Gröller,
A1 Anna Vilanova,
A1 Javier Oliván Bescós,
A1 Rachel E. Clough,
A1 Roy van Pelt,
K1 4D MRI blood-flow
K1 Probing
K1 Flow visualization
K1 Illustrative visualization
K1 Phase-contrast cine MRI
AB Insight into the dynamics of blood-flow considerably improves the understanding of the complex cardiovascular system and its pathologies. Advances in MRI technology enable acquisition of 4D blood-flow data, providing quantitative blood-flow velocities over time. The currently typical slice-by-slice analysis requires a full mental reconstruction of the unsteady blood-flow field, which is a tedious and highly challenging task, even for skilled physicians. We endeavor to alleviate this task by means of comprehensive visualization and interaction techniques. In this paper we present a framework for pre-clinical cardiovascular research, providing tools to both interactively explore the 4D blood-flow data and depict the essential blood-flow characteristics. The framework encompasses a variety of visualization styles, comprising illustrative techniques as well as improved methods from the established field of flow visualization. Each of the incorporated styles, including exploded planar reformats, flow-direction highlights, and arrow-trails, locally captures the blood-flow dynamics and may be initiated by an interactively probed vessel cross-section. Additionally, we present the results of an evaluation with domain experts, measuring the value of each of the visualization styles and related rendering parameters.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.153
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.153

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1348
TI Supine and Prone Colon Registration Using Quasi-Conformal Mapping
A1 Krishna Chaitanya Gurijala,
A1 Arie Kaufman,
A1 Wei Zeng,
A1 Joseph Marino,
A1 Xianfeng Gu,
K1 Data registration
K1 geometry-based techniques
K1 medical visualization
K1 mathematical foundations for visualization.
AB In virtual colonoscopy, CT scans are typically acquired with the patient in both supine (facing up) and prone (facing down) positions. The registration of these two scans is desirable so that the user can clarify situations or confirm polyp findings at a location in one scan with the same location in the other, thereby improving polyp detection rates and reducing false positives. However, this supine-prone registration is challenging because of the substantial distortions in the colon shape due to the patient's change in position. We present an efficient algorithm and framework for performing this registration through the use of conformal geometry to guarantee that the registration is a diffeomorphism (a one-to-one and onto mapping). The taeniae coli and colon flexures are automatically extracted for each supine and prone surface, employing the colon geometry. The two colon surfaces are then divided into several segments using the flexures, and each segment is cut along a taenia coli and conformally flattened to the rectangular domain using holomorphic differentials. The mean curvature is color encoded as texture images, from which feature points are automatically detected using graph cut segmentation, mathematic morphological operations, and principal component analysis. Corresponding feature points are found between supine and prone and are used to adjust the conformal flattening to be quasi-conformal, such that the features become aligned. We present multiple methods of visualizing our results, including 2D flattened rendering, corresponding 3D endoluminal views, and rendering of distortion measurements. We demonstrate the efficiency and efficacy of our registration method by illustrating matched views on both the 2D flattened colon images and in the 3D volume rendered colon endoluminal view. We analytically evaluate the correctness of the results by measuring the distance between features on the registered colons.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.200
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.200

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1358
TI Uncertainty-Aware Guided Volume Segmentation
A1 Jörg-Stefan Praßni,
A1 Timo Ropinski,
A1 Klaus Hinrichs,
K1 volume segmentation
K1 uncertainty
K1 classification
K1 random walker
AB Although direct volume rendering is established as a powerful tool for the visualization of volumetric data, efficient and reliable feature detection is still an open topic. Usually, a tradeoff between fast but imprecise classification schemes and accurate but time-consuming segmentation techniques has to be made. Furthermore, the issue of uncertainty introduced with the feature detection process is completely neglected by the majority of existing approaches.In this paper we propose a guided probabilistic volume segmentation approach that focuses on the minimization of uncertainty. In an iterative process, our system continuously assesses uncertainty of a random walker-based segmentation in order to detect regions with high ambiguity, to which the user's attention is directed to support the correction of potential misclassifications. This reduces the risk of critical segmentation errors and ensures that information about the segmentation's reliability is conveyed to the user in a dependable way. In order to improve the efficiency of the segmentation process, our technique does not only take into account the volume data to be segmented, but also enables the user to incorporate classification information. An interactive workflow has been achieved by implementing the presented system on the GPU using the OpenCL API. Our results obtained for several medical data sets of different modalities, including brain MRI and abdominal CT, demonstrate the reliability and efficiency of our approach.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.208
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.208

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1366
TI Exploration and Visualization of Segmentation Uncertainty using Shape and Appearance Prior Information
A1 Ghassan Hamarneh,
A1 Ahmed Saad,
A1 Torsten Möller,
K1 Uncertainty visualization
K1 Medical imaging
K1 Probabilistic segmentation
AB We develop an interactive analysis and visualization tool for probabilistic segmentation in medical imaging. The originality of our approach is that the data exploration is guided by shape and appearance knowledge learned from expert-segmented images of a training population. We introduce a set of multidimensional transfer function widgets to analyze the multivariate probabilistic field data. These widgets furnish the user with contextual information about conformance or deviation from the population statistics. We demonstrate the user's ability to identify suspicious regions (e.g. tumors) and to correct the misclassification results. We evaluate our system and demonstrate its usefulness in the context of static anatomical and time-varying functional imaging datasets.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.152
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.152

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1376
TI Edge Aware Anisotropic Diffusion for 3D Scalar Data
A1 Zahid Hossain,
A1 Torsten Möller,
K1 Anisotropic diffusion
K1 PDE
K1 De-noising
K1 Scale-Space
K1 Principle Curvatures
AB In this paper we present a novel anisotropic diffusion model targeted for 3D scalar field data. Our model preserves material boundaries as well as fine tubular structures while noise is smoothed out. One of the major novelties is the use of the directional second derivative to define material boundaries instead of the gradient magnitude for thresholding. This results in a diffusion model that has much lower sensitivity to the diffusion parameter and smoothes material boundaries consistently compared to gradient magnitude based techniques. We empirically analyze the stability and convergence of the proposed diffusion and demonstrate its de-noising capabilities for both analytic and real data. We also discuss applications in the context of volume rendering.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.147
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.147

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1396
TI Articulated Planar Reformation for Change Visualization in Small Animal Imaging
A1 Jouke Dijkstra,
A1 Martin Baiker,
A1 Charl P. Botha,
A1 Peter Kok,
A1 Frits H. Post,
A1 Clemens W.G.M. Löwik,
A1 Boudewijn P.F. Lelieveldt,
A1 Emile A. Hendriks,
K1 small animal imaging
K1 comparative visualization
K1 multi-timepoint
K1 molecular imaging
K1 articulated planar reformation
AB The analysis of multi-timepoint whole-body small animal CT data is greatly complicated by the varying posture of the subjectat different timepoints. Due to these variations, correctly relating and comparing corresponding regions of interest is challenging.In addition, occlusion may prevent effective visualization of these regions of interest. To address these problems, we have developeda method that fully automatically maps the data to a standardized layout of sub-volumes, based on an articulated atlas registration.We have dubbed this process articulated planar reformation, or APR. A sub-volume can be interactively selected for closer inspectionand can be compared with the corresponding sub-volume at the other timepoints, employing a number of different comparative visualization approaches. We provide an additional tool that highlights possibly interesting areas based on the change of bone densitybetween timepoints. Furthermore we allow visualization of the local registration error, to give an indication of the accuracy of theregistration. We have evaluated our approach on a case that exhibits cancer-induced bone resorption.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.134
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.134

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1405
TI Volumetric Modeling in Laser BPH Therapy Simulation
A1 Yunhe Shen,
A1 Xiangmin Zhou,
A1 Robert Sweet,
A1 Nan Zhang,
K1 Volume modeling
K1 volume CSG
K1 controlled-volume vaporization
K1 medical simulation
K1 laser BPH simulator
AB In this paper, we introduce a novel application of volume modeling techniques on laser Benign Prostatic Hyperplasia (BPH) therapy simulation. The core technique in our system is an algorithm for simulating the tissue vaporization process by laser heating. Different from classical volume CSG operations, our technique takes experimental data as the guidance to determine the vaporization amount so that only a specified amount of tissue is vaporized in each time. Our algorithm uses a predictor-corrector strategy. First, we apply the classical CSG algorithm on a tetrahedral grid based distance field to estimate the vaporized tissue amount. Then, a volume-correction phase is applied on the distance field. To improve the performance, we further propose optimization approaches for efficient implementation.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.221
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.221

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1421
TI Noodles: A Tool for Visualization of Numerical Weather Model Ensemble Uncertainty
A1 Song Zhang,
A1 Jamie Dyer,
A1 Philip Amburn,
A1 Andrew Mercer,
A1 Jibonananda Sanyal,
A1 Robert Moorhead,
K1 Uncertainty visualization
K1 weather ensemble
K1 geographic/geospatial visualization
K1 glyph-based techniques
K1 timevarying data
K1 qualitative evaluation
AB Numerical weather prediction ensembles are routinely used for operational weather forecasting. The members of these ensembles are individual simulations with either slightly perturbed initial conditions or different model parameterizations, or occasionally both. Multi-member ensemble output is usually large, multivariate, and challenging to interpret interactively. Forecast meteorologists are interested in understanding the uncertainties associated with numerical weather prediction; specifically variability between the ensemble members. Currently, visualization of ensemble members is mostly accomplished through spaghetti plots of a single mid-troposphere pressure surface height contour. In order to explore new uncertainty visualization methods, the Weather Research and Forecasting (WRF) model was used to create a 48-hour, 18 member parameterization ensemble of the 13 March 1993 "Superstorm". A tool was designed to interactively explore the ensemble uncertainty of three important weather variables: water-vapor mixing ratio, perturbation potential temperature, and perturbation pressure. Uncertainty was quantified using individual ensemble member standard deviation, inter-quartile range, and the width of the 95% confidence interval. Bootstrapping was employed to overcome the dependence on normality in the uncertainty metrics. A coordinated view of ribbon and glyph-based uncertainty visualization, spaghetti plots, iso-pressure colormaps, and data transect plots was provided to two meteorologists for expert evaluation. They found it useful in assessing uncertainty in the data, especially in finding outliers in the ensemble run and therefore avoiding the WRF parameterizations that lead to these outliers. Additionally, the meteorologists could identify spatial regions where the uncertainty was significantly high, allowing for identification of poorly simulated storm environments and physical interpretation of these model issues.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.181
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.181

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1431
TI Analysis of Recurrent Patterns in Toroidal Magnetic Fields
A1 Joshua Breslau,
A1 Scott Kruger,
A1 Allen Sanderson,
A1 David Pugmire,
A1 Guoning Chen,
A1 Xavier Tricoche,
K1 Confined magnetic fusion
K1 magnetic field visualization
K1 Poincaré map
K1 periodic magnetic fieldlines
K1 recurrent patterns
AB In the development of magnetic confinement fusion which will potentially be a future source for low cost power, physicists must be able to analyze the magnetic field that confines the burning plasma. While the magnetic field can be described as a vector field, traditional techniques for analyzing the field's topology cannot be used because of its Hamiltonian nature. In this paper we describe a technique developed as a collaboration between physicists and computer scientists that determines the topology of a toroidal magnetic field using fieldlines with near minimal lengths. More specifically, we analyze the Poincaré map of the sampled fieldlines in a Poincaré section including identifying critical points and other topological features of interest to physicists. The technique has been deployed into an interactiveparallel visualization tool which physicists are using to gain new insight into simulations of magnetically confined burning plasmas.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.133
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.133

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1441
TI Interactive Visualization of Hyperspectral Images of Historical Documents
A1 Michael Brown,
A1 Shaojie Zhuo,
A1 Seon Joo Kim,
A1 Fanbo Deng,
A1 Chi-Wing Fu,
K1 Hyperspectral visualization
K1 data exploration
K1 image fusion
K1 document processing and analysis
AB This paper presents an interactive visualization tool to study and analyze hyperspectral images (HSI) of historical documents. This work is part of a collaborative effort with the Nationaal Archief of the Netherlands (NAN) and Art Innovation, a manufacturer of hyperspectral imaging hardware designed for old and fragile documents. The NAN is actively capturing HSI of historical documents for use in a variety of tasks related to the analysis and management of archival collections, from ink and paper analysis to monitoring the effects of environmental aging. To assist their work, we have developed a comprehensive visualization tool that offers an assortment of visualization and analysis methods, including interactive spectral selection, spectral similarity analysis, time-varying data analysis and visualization, and selective spectral band fusion. This paper describes our visualization software and how it is used to facilitate the tasks needed by our collaborators. Evaluation feedback from our collaborators on how this tool benefits their work is included.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.172
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.172

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1449
TI Interactive Visual Analysis of Multiple Simulation Runs Using the Simulation Model View: Understanding and Tuning of an Electronic Unit Injector
A1 Andreas Ammer,
A1 Denis Gracanin,
A1 Kresimir Matkovic,
A1 Mario Jelovic,
A1 Helwig Hauser,
A1 Alan Lez,
K1 visualization in physical sciences and engineering
K1 time series data
K1 coordinated multiple views
AB Multiple simulation runs using the same simulation model with different values of control parameters generate a large data set that captures the behavior of the modeled phenomenon. However, there is a conceptual and visual gap between the simulation model behavior and the data set that makes data analysis more difficult. We propose a simulation model view that helps to bridge that gap by visually combining the simulation model description and the generated data. The simulation model view provides a visual outline of the simulation process and the corresponding simulation model. The view is integrated in a Coordinated Multiple Views ;(CMV) system. As the simulation model view provides a limited display space, we use three levels of details. We explored the use of the simulation model view, in close collaboration with a domain expert, to understand and tune an electronic unit injector (EUI). We also developed analysis procedures based on the view. The EUI is mostly used in heavy duty Diesel engines. We were mainly interested in understanding the model and how to tune it for three different operation modes: low emission, low consumption, and high power. Very positive feedback from the domain expert shows that the use of the simulation model view and the corresponding ;analysis procedures within a CMV system represents an effective technique for interactive visual analysis of multiple simulation runs.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.171
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.171

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1458
TI World Lines
A1 Eduard Gröller,
A1 Raphael Fuchs,
A1 Jürgen Waser,
A1 Benjamin Schindler,
A1 Günther Blöschl,
A1 Hrvoje Ribicic,
K1 Problem solving environment
K1 decision making
K1 simulation steering
K1 parallel worlds
K1 CFD
K1 smoothed particle hydrodynamics
AB In this paper we present World Lines as a novel interactive visualization that provides complete control over multiple heterogeneous simulation runs. In many application areas, decisions can only be made by exploring alternative scenarios. The goal of the suggested approach is to support users in this decision making process. In this setting, the data domain is extended to a set of alternative worlds where only one outcome will actually happen. World Lines integrate simulation, visualization and computational steering into a single unified system that is capable of dealing with the extended solution space. World Lines represent simulation runs as causally connected tracks that share a common time axis. This setup enables users to interfere and add new information quickly. A World Line is introduced as a visual combination of user events and their effects in order to present a possible future. To quickly find the most attractive outcome, we suggest World Lines as the governing component in a system of multiple linked views and a simulation component. World Lines employ linking and brushing to enable comparative visual analysis of multiple simulations in linked views. Analysis results can be mapped to various visual variables that World Lines provide in order to highlight the most compelling solutions. To demonstrate this technique we present a flooding scenario and show the usefulness of the integrated approach to support informed decision making.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.223
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.223

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1468
TI Result-Driven Exploration of Simulation Parameter Spaces for Visual Effects Design
A1 Torsten Möller,
A1 Stefan Bruckner,
K1 Visual exploration
K1 visual effects
K1 clustering
K1 time-dependent volume data
AB Graphics artists commonly employ physically-based simulation for the generation of effects such as smoke, explosions, and similar phenomena. The task of finding the correct parameters for a desired result, however, is difficult and time-consuming as current tools provide little to no guidance. In this paper, we present a new approach for the visual exploration of such parameter spaces. Given a three-dimensional scene description, we utilize sampling and spatio-temporal clustering techniques to generate a concise overview of the achievable variations and their temporal evolution. Our visualization system then allows the user to explore the simulation space in a goal-oriented manner. Animation sequences with a set of desired characteristics can be composed using a novel search-by-example approach and interactive direct volume rendering is employed to provide instant visual feedback.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.190
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.190

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1477
TI Visual Optimality and Stability Analysis of 3DCT Scan Positions
A1 Michael Reiter,
A1 Artem Amirkhanov,
A1 Christoph Heinzl,
A1 Eduard Gröller,
K1 Industrial 3DCT
K1 simulation
K1 Radon-space analysis
K1 stability analysis
K1 penetration-length analysis
AB Industrial cone-beam X-Ray computed tomography (CT) systems often face problems due to artifacts caused by a bad placement of the specimen on the rotary plate. This paper presents a visual-analysis tool for CT systems, which provides a simulation-based preview and estimates artifacts and deviations of a specimen's placement using the corresponding 3D geometrical surface model as input. The presented tool identifies potentially good or bad placements of a specimen and regions of a specimen, which cause the major portion of artefacts. The tool can be used for a preliminary analysis of the specimen before CT scanning, in order to determine the optimal way of placing the object. The analysis includes: penetration lengths, placement stability and an investigation in Radon space. Novel visualization techniques are applied to the simulation data. A stability widget is presented for determining the placement parameters' robustness. The performance and the comparison of results provided by the tool compared with real world data is demonstrated using two specimens.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.214
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.214

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1487
TI Pre-Integrated Volume Rendering with Non-Linear Gradient Interpolation
A1 Jean-Michel Dischler,
A1 Stéphane Marchesin,
A1 Alexandre Ancel,
A1 Amel Guetat,
K1 direct volume rendering
K1 pre-integration
K1 gradient interpolation
AB Shading is an important feature for the comprehension of volume datasets, but is difficult to implement accurately. Current techniques based on pre-integrated direct volume rendering approximate the volume rendering integral by ignoring non-linear gradient variations between front and back samples, which might result in cumulated shading errors when gradient variations are important and / or when the illumination function features high frequencies. In this paper, we explore a simple approach for pre-integrated volume rendering with non-linear gradient interpolation between front and back samples. We consider that the gradient smoothly varies along a quadratic curve instead of a segment in-between consecutive samples. This not only allows us to compute more accurate shaded pre-integrated look-up tables, but also allows us to more efficiently process shading amplifying effects, based on gradient filtering. An interesting property is that the pre-integration tables we use remain two-dimensional as for usual pre-integrated classification. We conduct experiments using a full hardware approach with the Blinn-Phong illumination model as well as with a non-photorealistic illumination model.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.187
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.187

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1495
TI Gradient Estimation Revitalized
A1 Laurent Condat,
A1 Torsten Möller,
A1 Usman Alim,
K1 Derivative
K1 Gradient
K1 Reconstruction
K1 Sampling
K1 Lattice
K1 Body Centered Cubic Lattice
K1 Interpolation
K1 Approximation
K1 Frequency Error Kernel
AB We investigate the use of a Fourier-domain derivative error kernel to quantify the error incurred while estimating the gradient of a function from scalar point samples on a regular lattice. We use the error kernel to show that gradient reconstruction quality is significantly enhanced merely by shifting the reconstruction kernel to the centers of the principal lattice directions. Additionally, we exploit the algebraic similarities between the scalar and derivative error kernels to design asymptotically optimal gradient estimation filters that can be factored into an infinite impulse response interpolation prefilter and a finite impulse response directional derivative filter. This leads to a significant performance gain both in terms of accuracy and computational efficiency. The interpolation prefilter provides an accurate scalar approximation and can be re-used to cheaply compute directional derivatives on-the-fly without the need to store gradients. We demonstrate the impact of our filters in the context of volume rendering of scalar data sampled on the Cartesian and Body-Centered Cubic lattices. Our results rival those obtained from other competitive gradient estimation methods while incurring no additional computational or storage overhead.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.160
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.160

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1505
TI Direct Interval Volume Visualization
A1 Marco Ament,
A1 Hamish Carr,
A1 Daniel Weiskopf,
K1 direct volume rendering
K1 interval volume
K1 isosurface
K1 ray casting
K1 preintegration
K1 scale-invariant opacity
AB We extend direct volume rendering with a unified model for generalized isosurfaces, also called interval volumes, allowing a wider spectrum of visual classification. We generalize the concept of scale-invariant opacity—typical for isosurface rendering—to semi-transparent interval volumes. Scale-invariant rendering is independent of physical space dimensions and therefore directly facilitates the analysis of data characteristics. Our model represents sharp isosurfaces as limits of interval volumes and combines them with features of direct volume rendering. Our objective is accurate rendering, guaranteeing that all isosurfaces and interval volumes are visualized in a crack-free way with correct spatial ordering. We achieve simultaneous direct and interval volume rendering by extending preintegration and explicit peak finding with data-driven splitting of ray integration and hybrid computation in physical and data domains. Our algorithm is suitable for efficient parallel processing for interactive applications as demonstrated by our CUDA implementation.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.145
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.145

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1515
TI VDVR: Verifiable Volume Visualization of Projection-Based Data
A1 Ziyi Zheng,
A1 Klaus Mueller,
A1 Wei Xu,
K1 Direct volume rendering
K1 computed tomography
K1 filtered back-projection
K1 verifiable visualization
AB Practical volume visualization pipelines are never without compromises and errors. A delicate and often-studied component is the interpolation of off-grid samples, where aliasing can lead to misleading artifacts and blurring, potentially hiding fine details of critical importance. The verifiable visualization framework we describe aims to account for these errors directly in the volume generation stage, and we specifically target volumetric data obtained via computed tomography (CT) reconstruction. In this case the raw data are the X-ray projections obtained from the scanner and the volume data generation process is the CT algorithm. Our framework informs the CT reconstruction process of the specific filter intended for interpolation in the subsequent visualization process, and this in turn ensures an accurate interpolation there at a set tolerance. Here, we focus on fast trilinear interpolation in conjunction with an octree-type mixed resolution volume representation without T-junctions. Efficient rendering is achieved by a space-efficient and locality-optimized representation, which can straightforwardly exploit fast fixed-function pipelines on GPUs.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.211
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.211

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1525
TI Fast High-Quality Volume Ray Casting with Virtual Samplings
A1 Jinwook Seo,
A1 Jihye Yun,
A1 Byonghyo Shim,
A1 Yeong-Gil Shin,
A1 Bohyoung Kim,
A1 Byeonghun Lee,
K1 direct volume rendering
K1 GPU
K1 high quality
K1 curve interpolation.
AB Volume ray-casting with a higher order reconstruction filter and/or a higher sampling rate has been adopted in direct volume rendering frameworks to provide a smooth reconstruction of the volume scalar and/or to reduce artifacts when the combined frequency of the volume and transfer function is high. While it enables high-quality volume rendering, it cannot support interactive rendering due to its high computational cost. In this paper, we propose a fast high-quality volume ray-casting algorithm which effectively increases the sampling rate. While a ray traverses the volume, intensity values are uniformly reconstructed using a high-order convolution filter. Additional samplings, referred to as virtual samplings, are carried out within a ray segment from a cubic spline curve interpolating those uniformly reconstructed intensities. These virtual samplings are performed by evaluating the polynomial function of the cubic spline curve via simple arithmetic operations. The min max blocks are refined accordingly for accurate empty space skipping in the proposed method. Experimental results demonstrate that the proposed algorithm, also exploiting fast cubic texture filtering supported by programmable GPUs, offers renderings as good as a conventional ray-casting algorithm using high-order reconstruction filtering at the same sampling rate, while delivering 2.5x to 3.3x rendering speed-up.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.155
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.155

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1533
TI Efficient High-Quality Volume Rendering of SPH Data
A1 Stefan Auer,
A1 Roland Fraedrich,
A1 Rüdiger Westermann,
K1 Particle visualization
K1 volume rendering
K1 ray-casting
K1 GPU resampling
AB High quality volume rendering of SPH data requires a complex order-dependent resampling of particle quantities along the view rays. In this paper we present an efficient approach to perform this task using a novel view-space discretization of the simulation domain. Our method draws upon recent work on GPU-based particle voxelization for the efficient resampling of particles into uniform grids. We propose a new technique that leverages a perspective grid to adaptively discretize the view-volume, giving rise to a continuous level-of-detail sampling structure and reducing memory requirements compared to a uniform grid. In combination with a level-of-detail representation of the particle set, the perspective grid allows effectively reducing the amount of primitives to be processed at run-time. We demonstrate the quality and performance of our method for the rendering of fluid and gas dynamics SPH simulations consisting of many millions of particles.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.148
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.148

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1541
TI Fast, Memory-Efficient Cell Location in Unstructured Grids for Visualization
A1 Kenneth I. Joy,
A1 Christoph Garth,
K1 unstructured grids
K1 cell location
K1 interpolation
K1 vector field visualization
AB Applying certain visualization techniques to datasets described on unstructured grids requires the interpolation of variables of interest at arbitrary locations within the dataset's domain of definition. Typical solutions to the problem of finding the grid element enclosing a given interpolation point make use of a variety of spatial subdivision schemes. However, existing solutions are memory- intensive, do not scale well to large grids, or do not work reliably on grids describing complex geometries. In this paper, we propose a data structure and associated construction algorithm for fast cell location in unstructured grids, and apply it to the interpolation problem. Based on the concept of bounding interval hierarchies, the proposed approach is memory-efficient, fast and numerically robust. We examine the performance characteristics of the proposed approach and compare it to existing approaches using a number of benchmark problems related to vector field visualization. Furthermore, we demonstrate that our approach can successfully accommodate large datasets, and discuss application to visualization on both CPUs and GPUs.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.156
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.156

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1551
TI Visualization by Proxy: A Novel Framework for Deferred Interaction with Volume Data
A1 Anna Tikhonova,
A1 Kwan-Liu Ma,
A1 Carlos D. Correa,
K1 volume visualization
K1 deferred interaction
K1 image-based rendering
K1 volume distortion camera
AB Interactivity is key to exploration of volume data. Interactivity may be hindered due to many factors, e.g. large data size,high resolution or complexity of a data set, or an expensive rendering algorithm. We present a novel framework for visualizing volumedata that enables interactive exploration using proxy images, without accessing the original 3D data. Data exploration using directvolume rendering requires multiple (often redundant) accesses to possibly large amounts of data. The notion of visualization by proxyrelies on the ability to defer operations traditionally used for exploring 3D data to a more suitable intermediate representation forinteraction - proxy images. Such operations include view changes, transfer function exploration, and relighting. While previous workhas addressed specific interaction needs, we provide a complete solution that enables real-time interaction with large data sets andhas low hardware and storage requirements.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.215
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.215

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1560
TI Interactive Vector Field Feature Identification
A1 Luis Gustavo Nonato,
A1 Cláudio T. Silva,
A1 Joel Daniels II,
A1 Erik W. Anderson,
K1 vector field
K1 data clustering
K1 feature classification
K1 high-dimensional data
K1 user interaction
AB We introduce a flexible technique for interactive exploration of vector field data through classification derived from userspecified feature templates. Our method is founded on the observation that, while similar features within the vector field may bespatially disparate, they share similar neighborhood characteristics. Users generate feature-based visualizations by interactivelyhighlighting well-accepted and domain specific representative feature points. Feature exploration begins with the computation ofattributes that describe the neighborhood of each sample within the input vector field. Compilation of these attributes forms a representation of the vector field samples in the attribute space. We project the attribute points onto the canonical 2D plane to enableinteractive exploration of the vector field using a painting interface. The projection encodes the similarities between vector field pointswithin the distances computed between their associated attribute points. The proposed method is performed at interactive rates forenhanced user experience and is completely flexible as showcased by the simultaneous identification of diverse feature types.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.170
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.170

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1569
TI Interactive Separating Streak Surfaces
A1 Rüdiger Westermann,
A1 Florian Ferstl,
A1 Holger Theisel,
A1 Kai Bürger,
K1 Unsteady flow visualization
K1 feature extraction
K1 streak surface generation
K1 GPUs
AB Streak surfaces are among the most important features to support 3D unsteady flow exploration, but they are also among the computationally most demanding. Furthermore, to enable a feature driven analysis of the flow, one is mainly interested in streak surfaces that show separation profiles and thus detect unstable manifolds in the flow. The computation of such separation surfaces requires to place seeding structures at the separation locations and to let the structures move correspondingly to these locations in the unsteady flow. Since only little knowledge exists about the time evolution of separating streak surfaces, at this time, an automated exploration of 3D unsteady flows using such surfaces is not feasible. Therefore, in this paper we present an interactive approach for the visual analysis of separating streak surfaces. Our method draws upon recent work on the extraction of Lagrangian coherent structures (LCS) and the real-time visualization of streak surfaces on the GPU. We propose an interactive technique for computing ridges in the finite time Lyapunov exponent (FTLE) field at each time step, and we use these ridges as seeding structures to track streak surfaces in the time-varying flow. By showing separation surfaces in combination with particle trajectories, and by letting the user interactively change seeding parameters such as particle density and position, visually guided exploration of separation profiles in 3D is provided. To the best of our knowledge, this is the first time that the reconstruction and display of semantic separable surfaces in 3D unsteady flows can be performed interactively, giving rise to new possibilities for gaining insight into complex flow phenomena.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.169
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.169

RT Journal Article
JF IEEE Transactions on Visualization & Computer Graphics
YR 2010
VO 16
IS
SP 1413
TI Scalable Multi-variate Analytics of Seismic and Satellite-based Observational Data
A1 Xiaoru Yuan,
A1 Peihong Guo,
A1 Jian Huang,
A1 Wesley Kendall,
A1 He Xiao,
A1 Yongxian Zhang,
A1 Hanqi Guo,
K1 Earth Science Visualization
K1 Multivariate Visualization
K1 Seismic Data
K1 Scalable Visualization
AB Over the past few years, large human populations around the world have been affected by an increase in significant seismic activities. For both conducting basic scientific research and for setting critical government policies, it is crucial to be able to explore and understand seismic and geographical information obtained through all scientific instruments. In this work, we present a visual analytics system that enables explorative visualization of seismic data together with satellite-based observational data, and introduce a suite of visual analytical tools. Seismic and satellite data are integrated temporally and spatially. Users can select temporal ;and spatial ranges to zoom in on specific seismic events, as well as to inspect changes both during and after the events. Tools for designing high dimensional transfer functions have been developed to enable efficient and intuitive comprehension of the multi-modal data. Spread-sheet style comparisons are used for data drill-down as well as presentation. Comparisons between distinct seismic events are also provided for characterizing event-wise differences. Our system has been designed for scalability in terms of data size, complexity (i.e. number of modalities), and varying form factors of display environments.
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 1077-2626
LA English
DO 10.1109/TVCG.2010.192
LK http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.192