EuroVis08: Joint Eurographics - IEEE VGTC Symposium on Visualization

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/397

Particle Level Set Advection for the Interactive Visualization of Unsteady 3D Flow

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Cuntz, Nicolas

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Kolb, Andreas

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Strzodka, Robert

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Weiskopf, Daniel

Physically-based Dye Advection for Flow Visualization

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Li, Guo-Shi

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Tricoche, Xavier

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Hansen, Charles

Animating Causal Overlays

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Bartram, Lyn

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Yao, Miao

Extraction Of Feature Lines On Surface Meshes Based On Discrete Morse Theory

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Sahner, Jan

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Weber, Britta

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Prohaska, Steffen

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Lamecker, Hans

Generating Color Palettes using Intuitive Parameters

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Wijffelaars, Martijn

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Vliegen, Roel

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Wijk, Jarke J. van

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Linden, Erik-Jan van der

Automatic Detection and Visualization of Distinctive Structures in 3D Unsteady Multi-fields

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Jänicke, Heike

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Böttinger, Michael

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Tricoche, Xavier

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Scheuermann, Gerik

Visual Comparison of Hierarchically Organized Data

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Holten, Danny

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Wijk, Jarke J. van

Concurrent Viewing of Multiple Attribute-Specific Subspaces

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Sisneros, Robert

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Johnson, C. Ryan

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Huang, Jian

A Four-level Focus + Context Approach to Interactive Visual Analysis of Temporal Features in Large Scientific Data

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Muigg, Philipp

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Kehrer, Johannes

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Oeltze, Steffen

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Piringer, Harald

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Doleisch, Helmut

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Preim, Bernhard

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Hauser, Helwig

Quality Isosurface Mesh Generation Using an Extended Marching Cubes Lookup Table

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Raman, Sundaresan

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Wenger, Rephael

Computing Local Signed Distance Fields for Large Polygonal Models

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Chang, Byungjoon

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Cha, Deukhyun

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Ihm, Insung

GPU Local Triangulation: an Interpolating Surface Reconstruction Algorithm

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Buchart, Carlos

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Borro, Diego

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Amundarain, Aiert

Interactive Visualization for Memory Reference Traces

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Choudhury, A. N. M. Imroz

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Potter, Kristin C.

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Parker, Steven G.

TimeRadarTrees: Visualizing Dynamic Compound Digraphs

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Burch, Michael

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Diehl, Stephan

Code Flows: Visualizing Structural Evolution of Source Code

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Telea, Alexandru

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Auber, David

Raycasting of Light Field Galleries from Volumetric Data

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Rezk-Salama, Christof

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Todt, Severin

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Kolb, Andreas

Interaction-Dependent Semantics for Illustrative Volume Rendering

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Rautek, Peter

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Bruckner, Stefan

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Gröller, M. Eduard

Illustrative Hybrid Visualization and Exploration of Anatomical and Functional Brain Data

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Jainek, Werner M.

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Born, Silvia

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Bartz, Dirk

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Straßer, Wolfgang

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Fischer, Jan

Geometry-driven Visualization of Microscopic Structures in Biology

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Mosaliganti, Kishore

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Machiraju, Raghu

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Huang, Kun

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Leone, Gustavo

Exploratory Visualization of Animal Kinematics Using Instantaneous Helical Axes

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Keefe, Daniel F.

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O'Brien, Trevor M.

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Baier, David B.

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Gatesy, Stephen M.

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Brainerd, Elizabeth L.

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Laidlaw, David H.

Classification and Uncertainty Visualization of Dendritic Spines from Optical Microscopy Imaging

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Janoos, Firdaus

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Nouansengsy, Boonthanome

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Xu, Xiaoyin

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Machiraju, Raghu

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Wong, Stephen T. C.

Visualizing Genome Expression and Regulatory Network Dynamics in Genomic and Metabolic Context

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Westenberg, Michel A.

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Hijum, S. A. F. T. van

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Kuipers, O. P.

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Roerdink, Jos B. T. M.

Towards Closing the Analysis Gap: Visual Generation of Decision Supporting Schemes from Raw Data

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May, Thorsten

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Kohlhammer, Jörn

Visual Analysis and Semantic Exploration of Urban LIDAR Change Detection

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Butkiewicz, Thomas

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Chang, Remco

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Wartell, Zachary

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Ribarsky, William

Density Displays for Data Stream Monitoring

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Hao, Ming

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Keim, Daniel A.

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Dayal, Umeshwar

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Oelke, Daniela

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Tremblay, Chantal

Investigative Visual Analysis of Global Terrorism

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Wang, Xiaoyu

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Miller, Erin

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Smarick, Kathleen

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Ribarsky, William

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Chang, Remco

Sound Tracing: Rendering Listener Specific Acoustic Room Properties

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Bellmann, Jens

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Michel, Frank

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Deines, Eduard

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Hering-Bertram, Martin

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Mohring, Jan

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Hagen, Hans

Visual Abstractions of Solvent Pathlines near Protein Cavities

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Bidmon, Katrin

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Grottel, Sebastian

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Bös, Fabian

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Pleiss, Jürgen

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Ertl, Thomas

COPERNICUS: Context-Preserving Engine for Route Navigation with Interactive User-modifiable Scaling

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Ziegler, Hartmut

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Keim, Daniel A.

Navigation and Exploration of Interconnected Pathways

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Streit, Marc

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Kalkusch, M.

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Kashofer, K.

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Schmalstieg, Dieter

Visual Inspection of Multivariate Graphs

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Pretorius, A. Johannes

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Wijk, Jarke J. van

FromWeb Data to Visualization via Ontology Mapping

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Gilson, Owen

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Silva, Nuno

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Grant, Phil W.

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Chen, Min

Results of a User Study on 2D Hurricane Visualization

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Martin, Joel P.

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II, J. Edward Swan

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II, Robert J. Moorhead

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Liu, Zhanping

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Cai, Shangshu

Centrality Based Visualization of Small World Graphs

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Ham, Frank van

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Wattenberg, Martin

Interactive Exploratory Visualization of 2D Vector Fields

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Isenberg, Tobias

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Everts, Maarten H.

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Grubert, Jens

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Carpendale, Sheelagh

Lagrangian Visualization of Flow-Embedded Surface Structures

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Garth, Christoph

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Wiebel, Alexander

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Tricoche, Xavier

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Joy, Ken

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Scheuermann, Gerik

Evaluation of Illustration-inspired Techniques for Time-varying Data Visualization

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Joshi, Alark

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Rheingans, Penny

Discrete Multi-Material Interface Reconstruction for Volume Fraction Data

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Anderson, John C.

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Garth, C.

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Duchaineau, Mark A.

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Joy, Kenneth I.

A Screen Space Quality Method for Data Abstraction

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Johansson, Jimmy

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Cooper, Matthew

Illustrative Parallel Coordinates

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McDonnell, Kevin T.

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Mueller, Klaus

Topology-Preserving lambda_2-based Vortex Core Line Detection for Flow Visualization

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Schafhitzel, Tobias

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Vollrath, Joachim E.

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Gois, Joao P.

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Weiskopf, Daniel

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Castelo, Antonio

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Ertl, Thomas

Visual Clustering in Parallel Coordinates

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Zhou, Hong

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Yuan, Xiaoru

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Qu, Huamin

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Cui, Weiwei

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Chen, Baoquan

Interactive Visualization of Multimodal Volume Data for Neurosurgical Tumor Treatment

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Rieder, Christian

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Ritter, Felix

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Raspe, Matthias

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Peitgen, Heinz-Otto

Virtual Klingler Dissection: Putting Fibers into Context

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Schultz, Thomas

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Sauber, Natascha

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Anwander, Alfred

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Theisel, Holger

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Seidel, Hans-Peter

Abstractive Representation and Exploration of Hierarchically Clustered Diffusion Tensor Fiber Tracts

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Chen, Wei

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Zhang, Song

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Correia, Stephen

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Ebert, David S.

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Now showing 1 - 45 of 45

Particle Level Set Advection for the Interactive Visualization of Unsteady 3D Flow
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Cuntz, Nicolas; Kolb, Andreas; Strzodka, Robert; Weiskopf, Daniel; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Typically, flow volumes are visualized by defining their boundary as iso-surface of a level set function. Grid-based level sets offer a good global representation but suffer from numerical diffusion of surface detail, whereas particlebased methods preserve details more accurately but introduce the problem of unequal global representation. The particle level set (PLS) method combines the advantages of both approaches by interchanging the information between the grid and the particles. Our work demonstrates that the PLS technique can be adapted to volumetric dye advection via streak volumes, and to the visualization by time surfaces and path volumes. We achieve this with a modified and extended PLS, including a model for dye injection. A new algorithmic interpretation of PLS is introduced to exploit the efficiency of the GPU, leading to interactive visualization. Finally, we demonstrate the high quality and usefulness of PLS flow visualization by providing quantitative results on volume preservation and by discussing typical applications of 3D flow visualization.
Physically-based Dye Advection for Flow Visualization
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Li, Guo-Shi; Tricoche, Xavier; Hansen, Charles; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Dye advection is widely used in experimental flow analysis but has seen less use for visualization in computational fluid dynamics. One possible reason for this disconnect is the inaccuracy of the texture-based approach, which is prone to artifacts caused by numeric diffusion and mass fluctuation. In this paper, we introduce a novel 2D dye advection scheme for flow visualization based on the concept of control volume analysis typically used in computational fluid dynamics. The evolution of dye patterns in the flow field is achieved by advecting individual control volumes, which collectively cover the entire spatial domain. The local variation of dye material, represented as a piecewise quasi-parabolic function, is integrated within each control volume resulting in mass conserving transport without excessive numerical diffusion. Due to its physically based formulation, this approach is capable of conveying intricate flow structures not shown in the traditional dye advection schemes while avoiding visual artifacts.
Animating Causal Overlays
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Bartram, Lyn; Yao, Miao; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Most approaches to representing causality, such as the common causal graph, require a separate and static view, but in many cases it is useful to add the dimension of causality to the context of an existing visualization. Building on research from perceptual psychology that shows the perception of causality is a low-level visual event derived from certain types of motion, we are investigating how to add animated causal representations, called visual causal vectors, onto other visualizations. We refer to these as causal overlays. Our initial experimental results show this approach has great potential but that extra cues are needed to elicit the perception of causality when the motions are overlaid on other graphical objects. In this paper we describe the approach and report on a study that examined two issues of this technique: how to accurately convey the causal flow and how to represent the strength of the causal effect.
Extraction Of Feature Lines On Surface Meshes Based On Discrete Morse Theory
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Sahner, Jan; Weber, Britta; Prohaska, Steffen; Lamecker, Hans; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
We present an approach for extracting extremal feature lines of scalar indicators on surface meshes, based on discrete Morse Theory. By computing initial Morse-Smale complexes of the scalar indicators of the mesh, we obtain a candidate set of extremal feature lines of the surface. A hierarchy of Morse-Smale complexes is computed by prioritizing feature lines according to a novel criterion and applying a cancellation procedure that allows us to select the most significant lines. Given the scalar indicators on the vertices of the mesh, the presented feature line extraction scheme is interpolation free and needs no derivative estimates. The technique is insensitive to noise and depends only on one parameter: the feature significance. We use the technique to extract surface features yielding impressive, non photorealistic images.
Generating Color Palettes using Intuitive Parameters
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Wijffelaars, Martijn; Vliegen, Roel; Wijk, Jarke J. van; Linden, Erik-Jan van der; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Color is widely used in data visualization to show data values. The proper selection of colors is critical to convey information correctly. In this paper, we present a technique for generating univariate lightness ordered palettes. These are specified via intuitive input parameters that are used define the appearance of the palette: number of colors, hue, lightness, saturation, contrast and hue range. The settings of the parameters are used to generate curves through CIELUV color space. This color space is used in order to correctly translate the requirements in terms of perceptual properties to a set of colors. The presented palette generation method enables users to specify palettes that have these perceptual properties, such as perceived order, equal perceived distance and equal importance. The technique has been integrated in MagnaView, a system for multivariate data visualization.
Automatic Detection and Visualization of Distinctive Structures in 3D Unsteady Multi-fields
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Jänicke, Heike; Böttinger, Michael; Tricoche, Xavier; Scheuermann, Gerik; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Current unsteady multi-field simulation data-sets consist of millions of data-points. To efficiently reduce this enormous amount of information, local statistical complexity was recently introduced as a method that identifies distinctive structures using concepts from information theory. Due to high computational costs this method was so far limited to 2D data. In this paper we propose a new strategy for the computation that is substantially faster and allows for a more precise analysis. The bottleneck of the original method is the division of spatio-temporal configurations in the field (light-cones) into different classes of behavior. The new algorithm uses a density-driven Voronoi tessellation for this task that more accurately captures the distribution of configurations in the sparsely sampled high-dimensional space. The efficient computation is achieved using structures and algorithms from graph theory. The ability of the method to detect distinctive regions in 3D is illustrated using flow and weather simulations.
Visual Comparison of Hierarchically Organized Data
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Holten, Danny; Wijk, Jarke J. van; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
We provide a novel visualization method for the comparison of hierarchically organized data. Our technique visualizes a pair of hierarchies that are to be compared and simultaneously depicts how these hierarchies are related by explicitly visualizing the relations between matching subhierarchies. Elements that are unique to each hierarchy are shown, as well as the way in which hierarchy elements are relocated, split or joined. The relations between hierarchy elements are visualized using Hierarchical Edge Bundles (HEBs). HEBs reduce visual clutter, they visually emphasize the aforementioned splits, joins, and relocations of subhierarchies, and they provide an intuitive way in which users can interact with the relations. The focus throughout this paper is on the comparison of different versions of hierarchically organized software systems, but the technique is applicable to other kinds of hierarchical data as well. Various data sets of actual software systems are used to show how our technique can be employed to easily spot splits, joins, and relocations of elements, how sorting both hierarchies with respect to each other facilitates comparison tasks, and how user interaction is supported.
Concurrent Viewing of Multiple Attribute-Specific Subspaces
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Sisneros, Robert; Johnson, C. Ryan; Huang, Jian; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
In this work we present a point classification algorithm for multi-variate data. Our method is based on the concept of attribute subspaces, which are derived from a set of user specified attribute target values. Our classification approach enables users to visually distinguish regions of saliency through concurrent viewing of these subspaces in single images. We also allow a user to threshold the data according to a specified distance from attribute target values. Based on the degree of thresholding, the remaining data points are assigned radii of influence that are used for the final coloring. This limits the view to only those points that are most relevant, while maintaining a similar visual context.
A Four-level Focus + Context Approach to Interactive Visual Analysis of Temporal Features in Large Scientific Data
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Muigg, Philipp; Kehrer, Johannes; Oeltze, Steffen; Piringer, Harald; Doleisch, Helmut; Preim, Bernhard; Hauser, Helwig; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
In this paper we present a new approach to the interactive visual analysis of time-dependent scientific data - both from measurements as well as from computational simulation - by visualizing a scalar function over time for each of tenthousands or even millions of sample points. In order to cope with overdrawing and cluttering, we introduce a new four-level method of focus+context visualization. Based on a setting of coordinated, multiple views (with linking and brushing), we integrate three different kinds of focus and also the context in every single view. Per data item we use three values (from the unit interval each) to represent to which degree the data item is part of the respective focus level. We present a color compositing scheme which is capable of expressing all three values in a meaningful way, taking semantics and their relations amongst each other (in the context of our multiple linked view setup) into account. Furthermore, we present additional image-based postprocessing methods to enhance the visualization of large sets of function graphs, including a texture-based technique based on line integral convolution (LIC). We also propose advanced brushing techniques which are specific to the timedependent nature of the data (in order to brush patterns over time more efficiently). We demonstrate the usefulness of the new approach in the context of medical perfusion data.
Quality Isosurface Mesh Generation Using an Extended Marching Cubes Lookup Table
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Raman, Sundaresan; Wenger, Rephael; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Computing Local Signed Distance Fields for Large Polygonal Models
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Chang, Byungjoon; Cha, Deukhyun; Ihm, Insung; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
The signed distance field for a polygonal model is a useful representation that facilitates efficient computation in many visualization and geometric processing tasks. Often it is more effective to build a local distance field only within a narrow band around the surface that holds local geometric information for the model. In this paper, we present a novel technique to construct a volumetric local signed distance field of a polygonal model. To compute the local field efficiently, exactly those cells that cross the polygonal surface are found first through a new voxelization method, building a list of intersecting triangles for each boundary cell. After their neighboring cells are classified, the triangle lists are exploited to compute the local signed distance field with minimized voxel-totriangle distance computations. While several efficient methods for computing the distance field, particularly those harnessing the graphics processing unit's (GPU's) processing power, have recently been proposed, we focus on a CPU-based technique, intended to deal flexibly with large polygonal models and high-resolution grids that are often too bulky for GPU computation.
GPU Local Triangulation: an Interpolating Surface Reconstruction Algorithm
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Buchart, Carlos; Borro, Diego; Amundarain, Aiert; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
A GPU capable method for surface reconstruction from unorganized point clouds without additional information, called GLT (GPU Local Triangulation), is presented. The main objective of this research is the generation of a GPU interpolating reconstruction based on local Delaunay triangulations, inspired by a pre-existing reconstruction algorithm. Current graphics hardware accelerated algorithms are approximating approaches, where the final triangulation is usually performed through either marching cubes or marching tetrahedras. GPU-compatible methods and data structures to perform normal estimation and the local triangulation have been developed, plus a variation of the Bitonic Merge Sort algorithm to work with multi-lists. Our method shows an average gain of one order of magnitude over previous research.
Interactive Visualization for Memory Reference Traces
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Choudhury, A. N. M. Imroz; Potter, Kristin C.; Parker, Steven G.; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
We present the Memory Trace Visualizer (MTV), a tool that provides interactive visualization and analysis of the sequence of memory operations performed by a program as it runs. As improvements in processor performance continue to outpace improvements in memory performance, tools to understand memory access patterns are in- creasingly important for optimizing data intensive programs such as those found in scientific computing. Using visual representations of abstract data structures, a simulated cache, and animating memory operations, MTV can expose memory performance bottlenecks and guide programmers toward memory system optimization opportu- nities. Visualization of detailed memory operations provides a powerful and intuitive way to expose patterns and discover bottlenecks, and is an important addition to existing statistical performance measurements.
TimeRadarTrees: Visualizing Dynamic Compound Digraphs
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Burch, Michael; Diehl, Stephan; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
The evolution of dependencies in information hierarchies can be modeled by sequences of compound digraphs with edge weights. In this paper we present a novel approach to visualize such sequences of graphs. It uses radial tree layout to draw the hierarchy, and circle sectors to represent the temporal change of edges in the digraphs. We have developed several interaction techniques that allow the users to explore the structural and temporal data. Smooth animations help them to track the transitions between views. The usefulness of the approach is illustrated by examples from very different application domains.
Code Flows: Visualizing Structural Evolution of Source Code
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Telea, Alexandru; Auber, David; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Understanding detailed changes done to source code is of great importance in software maintenance. We present Code Flows, a method to visualize the evolution of source code geared to the understanding of fine and mid-level scale changes across several file versions. We enhance an existing visual metaphor to depict software structure changes with techniques that emphasize both following unchanged code as well as detecting and highlighting important events such as code drift, splits, merges, insertions and deletions. The method is illustrated with the analysis of a real-world C++ code system.
Raycasting of Light Field Galleries from Volumetric Data
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Rezk-Salama, Christof; Todt, Severin; Kolb, Andreas; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
The paper describes a technique to generate high-quality light field representations from volumetric data. We show how light field galleries can be created to give unexperienced audiences access to interactive high-quality volume renditions. The proposed light field representation is lightweight with respect to storage and bandwidth capacity and is thus ideal as exchange format for visualization results, especially for web galleries. The approach expands an existing sphere-hemisphere parameterization for the light field with per-pixel depth. High-quality paraboloid maps from volumetric data are generated using GPU-based ray-casting or slicing approaches. Different layers, such as isosurfaces, but not restricted to, can be generated independently and composited in real time. This allows the user to interactively explore the model and to change visibility parameters at run-time.
Interaction-Dependent Semantics for Illustrative Volume Rendering
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Rautek, Peter; Bruckner, Stefan; Gröller, M. Eduard; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
In traditional illustration the choice of appropriate styles and rendering techniques is guided by the intention of the artist. For illustrative volume visualizations it is difficult to specify the mapping between the 3D data and the visual representation that preserves the intention of the user. The semantic layers concept establishes this mapping with a linguistic formulation of rules that directly map data features to rendering styles. With semantic layers fuzzy logic is used to evaluate the user defined illustration rules in a preprocessing step. In this paper we introduce interaction-dependent rules that are evaluated for each frame and are therefore computationally more expensive. Enabling interaction-dependent rules, however, allows the use of a new class of semantics, resulting in more expressive interactive illustrations. We show that the evaluation of the fuzzy logic can be done on the graphics hardware enabling the efficient use of interaction-dependent semantics. Further we introduce the flat rendering mode and discuss how different rendering parameters are influenced by the rule base. Our approach provides high quality illustrative volume renderings at interactive frame rates, guided by the specification of illustration rules.
Illustrative Hybrid Visualization and Exploration of Anatomical and Functional Brain Data
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Jainek, Werner M.; Born, Silvia; Bartz, Dirk; Straßer, Wolfgang; Fischer, Jan; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Common practice in brain research and brain surgery involves the multi-modal acquisition of brain anatomy and brain activation data. These highly complex three-dimensional data have to be displayed simultaneously in order to convey spatial relationships. Unique challenges in information and interaction design have to be solved in order to keep the visualization sufficiently complete and uncluttered at the same time. The visualization method presented in this paper addresses these issues by using a hybrid combination of polygonal rendering of brain structures and direct volume rendering of activation data. Advanced rendering techniques including illustrative display styles and ambient occlusion calculations enhance the clarity of the visual output. The presented rendering pipeline produces real-time frame rates and offers a high degree of configurability. Newly designed interaction and measurement tools are provided, which enable the user to explore the data at large, but also to inspect specific features closely. We demonstrate the system in the context of a cognitive neurosciences dataset. An initial informal evaluation shows that our visualization method is deemed useful for clinical research.
Geometry-driven Visualization of Microscopic Structures in Biology
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Mosaliganti, Kishore; Machiraju, Raghu; Huang, Kun; Leone, Gustavo; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
At a microscopic resolution, biological structures are composed of cells, red blood corpuscles (RBCs), cytoplasm and other microstructural components. There is a natural pattern in terms of distribution, arrangement and packing density of these components in biological organization. In this work, we propose to use N-point correlation functions to guide the analysis and exploration process in microscopic datasets. These functions provide useful feature spaces to aid segmentation and visualization tasks. We show 3D visualizations of mouse placenta tissue layers and mouse mammary ducts as well as 2D segmentation/tracking of clonal populations. Further confidence in our results stems from validation studies that were performed with manual ground-truth for segmentation.
Exploratory Visualization of Animal Kinematics Using Instantaneous Helical Axes
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Keefe, Daniel F.; O'Brien, Trevor M.; Baier, David B.; Gatesy, Stephen M.; Brainerd, Elizabeth L.; Laidlaw, David H.; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
We present novel visual and interactive techniques for exploratory visualization of animal kinematics using instantaneous helical axes (IHAs). The helical axis has been used in orthopedics, biomechanics, and structural mechanics as a construct for describing rigid body motion. Within biomechanics, recent imaging advances have made possible accurate high-speed measurements of individual bone positions and orientations during experiments. From this high-speed data, instantaneous helical axes of motion may be calculated. We address questions of effective interactive, exploratory visualization of this high-speed 3D motion data. A 3D glyph that encodes all parameters of the IHA in visual form is presented. Interactive controls are used to examine the change in the IHA over time and relate the IHA to anatomical features of interest selected by a user. The techniques developed are applied to a stereoscopic, interactive visualization of the mechanics of pig mastication and assessed by a team of evolutionary biologists who found interactive IHA-based analysis a useful addition to more traditional motion analysis techniques.
Classification and Uncertainty Visualization of Dendritic Spines from Optical Microscopy Imaging
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Janoos, Firdaus; Nouansengsy, Boonthanome; Xu, Xiaoyin; Machiraju, Raghu; Wong, Stephen T. C.; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Abstract Neuronal dendrites and their spines affect the connectivity of neural networks, and play a significant role in many neurological conditions. Neuronal function is observed to be closely correlated with the appearance, disappearance and morphology of the spines. Automatic 3-D reconstruction of neurons from light microscopy images, followed by the identification, classification and visualization of dendritic spines is therefore essential for studying neuronal physiology and biophysical properties. In this paper, we present a method to reconstruct dendrites using a surface representation of the dendrite. The 1-D skeleton of the dendritic surface is then extracted by a medial geodesic function that is robust and topologically correct. This is followed by a Bayesian identification and classification of the spines. The dendrite and spines are visualized in a manner that displays the spines' types and the inherent uncertainty in identification and classification. We also describe a user study conducted to validate the accuracy of the classification and the efficacy of the visualization.
Visualizing Genome Expression and Regulatory Network Dynamics in Genomic and Metabolic Context
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Westenberg, Michel A.; Hijum, S. A. F. T. van; Kuipers, O. P.; Roerdink, Jos B. T. M.; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
DNA microarrays are used to measure the expression levels of thousands of genes simultaneously. In a time series experiment, the gene expressions are measured as a function of time. We present an application for integrated visualization of genome expression and network dynamics in both regulatory networks and metabolic pathways. Integration of these two levels of cellular processes is necessary, since it provides the link between the measure- ments at the transcriptional level (gene expression levels approximated from microarray data) and the phenotype (the observable characteristics of an organism) at the functional and behavioral level. The integration requires visualization approaches besides traditional clustering and statistical analysis methods. Our application can (i) visualize the data from time series experiments in the context of a regulatory network and KEGG metabolic pathways; (ii) identify and visualize active regulatory subnetworks from the gene expression data; (iii) perform a statistical test to identify and subsequently visualize pathways that are affected by differentially expressed genes. We present a case study, which demonstrates that our approach and application both facilitates and speeds up data analysis tremendously in comparison to a more traditional approach that involves many manual, laborious, and error-prone steps.
Towards Closing the Analysis Gap: Visual Generation of Decision Supporting Schemes from Raw Data
(The Eurographics Association and Blackwell Publishing Ltd., 2008) May, Thorsten; Kohlhammer, Jörn; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
The derivation, manipulation and verification of analytical models from raw data is a process which requires a transformation of information across different levels of abstraction. We introduce a concept for the coupling of data classification and interactive visualization in order to make this transformation visible and steerable for the human user. Data classification techniques generate mappings that formally group data items into categories. Interactive visualization includes the user into an iterative refinement process. The user identifies and selects interesting patterns to define these categories. The following step is the transformation of a visible pattern into the formal definition of a classifier. In the last step the classifier is transformed back into a pattern that is blended with the original data in the same visual display. Our approach allows in intuitive assessment of a formal classifier and its model, the detection of outliers and the handling of noisy data using visual pattern-matching. We instantiated the concept using decision trees for classification and KVMaps as the visualization technique. The generation of a classifier from visual patterns and its verification is transformed from a cognitive to a mostly pre-cognitive task.
Visual Analysis and Semantic Exploration of Urban LIDAR Change Detection
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Butkiewicz, Thomas; Chang, Remco; Wartell, Zachary; Ribarsky, William; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Many previous approaches to detecting urban change from LIDAR point clouds interpolate the points into rasters, perform pixel-based image processing to detect changes, and produce 2D images as output. We present a method of LIDAR change detection that maintains accuracy by only using the raw, irregularly spaced LIDAR points, and extracts relevant changes as individual 3D models. We then utilize these models, alongside existing GIS data, within an interactive application that allows the chronological exploration of the changes to an urban environment. A three-tiered level-of-detail system maintains a scale-appropriate, legible visual representation across the entire range of view scales, from individual changes such as buildings and trees, to groups of changes such as new residential developments, deforestation, and construction sites, and finally to larger regions such as neighborhoods and districts of a city that are emerging or undergoing revitalization. Tools are provided to assist the visual analysis by urban planners and historians through semantic categorization and filtering of the changes presented.
Density Displays for Data Stream Monitoring
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Hao, Ming; Keim, Daniel A.; Dayal, Umeshwar; Oelke, Daniela; Tremblay, Chantal; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
In many business applications, large data workloads such as sales figures or process performance measures need to be monitored in real-time. The data analysts want to catch problems in flight to reveal the root cause of anomalies. Immediate actions need to be taken before the problems become too expensive or consume too many resources. In the meantime, analysts need to have the "big picture" of what the information is about. In this paper, we derive and analyze two real-time visualization techniques for managing density displays: (1) circular overlay displays which visualize large volumes of data without data shift movements after the display is full, thus freeing the analyst from adjusting the mental picture of the data after each data shift; and (2) variable resolution density displays which allow users to get the entire view without cluttering. We evaluate these techniques with respect to a number of evaluation measures, such as constancy of the display and usage of display space, and compare them to conventional displays with periodic shifts. Our real time data monitoring system also provides advanced interactions such as a local root cause analysis for further exploration. The applications using a number of real-world data sets show the wide applicability and usefulness of our ideas.
Investigative Visual Analysis of Global Terrorism
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Wang, Xiaoyu; Miller, Erin; Smarick, Kathleen; Ribarsky, William; Chang, Remco; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Recent increases in terrorist activity around the world have made analyzing and understanding such activities more critical than ever. With the help of organizations such as the National Center for the Study of Terrorism and Responses to Terrorism (START), we now have detailed historical information on each terrorist event around the world since 1970. However, due to the size and complexity of the data, identifying terrorists' patterns and trends has been difficult. To better enable investigators in understanding terrorist activities, we propose a visual analytical system that focuses on depicting one of the most fundamental concepts in investigative analysis, the five W's (who, what, where, when, and why). Views in our system are highly correlated, and each represents one of the W's. With this approach, an investigator can interactively explore terrorist activities efficiently and discover reasons of attacks (why) by identifying patterns temporally (when), geo-spatially (where), between multiple terrorist groups (who), and across different methods or modes of attacks (what). By coupling a global perspective with the details gleaned from asking these five questions, the system allows analysts to think both tactically and strategically.
Sound Tracing: Rendering Listener Specific Acoustic Room Properties
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Bellmann, Jens; Michel, Frank; Deines, Eduard; Hering-Bertram, Martin; Mohring, Jan; Hagen, Hans; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
We present an acoustic rendering approach visualizing the listener-specific contribution of frequency-dependent pressure fields on a scene geometry with acoustic reflection and scattering properties. Our method facilitates the evaluation of simulated acoustics showing the effect of simulation parameters like absorption and scattering. The image-based spatial localization of acoustic properties is complementary to the auditive evaluation by means of auralization. Our core contribution is a pressure-based acoustic rendering equation and a corresponding raytracing method applying techniques from photorealistic rendering to the field of simulated room acoustics. Applications are directed at the visualization of interference patterns and analyzing the impact of acoustic reflection parameters.
Visual Abstractions of Solvent Pathlines near Protein Cavities
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Bidmon, Katrin; Grottel, Sebastian; Bös, Fabian; Pleiss, Jürgen; Ertl, Thomas; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Water is known to play a crucial role in protein structure, flexibility and activity. The use of molecular dynamics simulations allows detailed studies of complex protein-solvent interactions. Cluster analysis and density-based approaches have been successfully used for the identification and analysis of conserved water molecules and hydration patterns of proteins. However, appropriate tools for analysing long-time molecular dynamics simulations with respect to tracking and visualising the paths of solvent molecules are lacking. Our method focuses on visualising the solvent paths entering and leaving cavities of the protein and allows to study the route and dynamics of the exchange of tightly bound internal water molecules with the bulk solvent. The proposed visualisation also represents dynamic properties such as direction and velocity in the solvent. Especially, by clustering similar pathlines with respect to designated properties the visualisation can be abstracted to represent the principal paths of solvent molecules through the cavities. Its application in the analysis of long-time scale molecular dynamics simulations not only confirmed conjectures based on previous manual observations made by chance, but also led to novel insights into the dynamical and structural role of water molecules and its interplay with protein structure.
COPERNICUS: Context-Preserving Engine for Route Navigation with Interactive User-modifiable Scaling
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Ziegler, Hartmut; Keim, Daniel A.; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
In this paper, we present an automated system for generating context-preserving route maps that depict navigation routes as a path between nodes and edges inside a topographic network. Our application identifies relevant context information to support navigation and orientation, and generates customizable route maps according to design principles that communicate all relevant context information clearly visible on one single page. Interactive scaling allows seamless transition between the original undistorted map and our new map design, and supports userspecified scaling of regions of interest to create personalized driving directions according to the drivers needs.
Navigation and Exploration of Interconnected Pathways
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Streit, Marc; Kalkusch, M.; Kashofer, K.; Schmalstieg, Dieter; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Visualizing pathways, i. e. models of cellular functional networks, is a challenging task in computer assisted biomedicine. Pathways are represented as large collections of interwoven graphs, with complex structures present in both the individual graphs and their interconnections. This situation requires the development of novel visualization techniques to allow efficient visual exploration. We present the Caleydo framework, which incorporates a number of approaches to handle such pathways. Navigation in the network of pathways is facilitated by a hierarchical approach which dynamically selects a working set of individual pathways for closer inspection. These pathways are interactively rendered together with visual interconnections in a 2.5D view using graphics hardware acceleration. The layout of individual graphs is not computed automatically, but taken from the KEGG and BioCarta databases, which use layouts that life scientists are familiar with. Therefore they encode essential meta-information. While the KEGG and BioCarta pathways use a pre-defined layout, interactions such as linking+ brushing, neighborhood search or detail on demand are still fully interactive in Caleydo. We have evaluated Caleydo with pathologists working on the determination of unknown gene functions. Informal experiences confirm that Caleydo is useful in both generating and validating such hypotheses. Even though the presented techniques are applied to medical pathways, the proposed way of interaction is not limited to cellular processes and therefore has the potential to open new possibilities in other fields of application.
Visual Inspection of Multivariate Graphs
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Pretorius, A. Johannes; Wijk, Jarke J. van; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Most graph visualization techniques focus on the structure of graphs and do not offer support for dealing with node attributes and edge labels. To enable users to detect relations and patterns in terms of data associated with nodes and edges, we present a technique where this data plays a more central role. Nodes and edges are clustered based on associated data. Via direct manipulation users can interactively inspect and query the graph. Questions that can be answered include, "which edge types are activated by specific node attributes?" and, "how and from where can I reach specific types of nodes?" To validate our approach we contrast it with current practice. We also provide several examples where our method was used to study transition graphs that model real-world systems.
FromWeb Data to Visualization via Ontology Mapping
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Gilson, Owen; Silva, Nuno; Grant, Phil W.; Chen, Min; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
In this paper, we propose a novel approach for automatic generation of visualizations from domain-specific data available on the web. We describe a general system pipeline that combines ontology mapping and probabilistic reasoning techniques. With this approach, a web page is first mapped to a Domain Ontology, which stores the semantics of a specific subject domain (e.g., music charts). The Domain Ontology is then mapped to one or more Visual Representation Ontologies, each of which captures the semantics of a visualization style (e.g., tree maps). To enable the mapping between these two ontologies, we establish a Semantic Bridging Ontology, which specifies the appropriateness of each semantic bridge. Finally each Visual Representation Ontology is mapped to a visualization using an external visualization toolkit. Using this approach, we have developed a prototype software tool, SemViz, as a realisation of this approach. By interfacing its Visual Representation Ontologies with public domain software such as ILOG Discovery and Prefuse, SemViz is able to generate appropriate visualizations automatically from a large collection of popular web pages for music charts without prior knowledge of these web pages.
Results of a User Study on 2D Hurricane Visualization
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Martin, Joel P.; II, J. Edward Swan; II, Robert J. Moorhead; Liu, Zhanping; Cai, Shangshu; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
We present the results from a user study looking at the ability of observers to mentally integrate wind direction and magnitude over a vector field. The data set chosen for the study is an MM5 (PSU/NCAR Mesoscale Model) simulation of Hurricane Lili over the Gulf of Mexico as it approaches the southeastern United States. Nine observers participated in the study. This study investigates the effect of layering on the observer's ability to determine the magnitude and direction of a vector field. We found a tendency for observers to underestimate the magnitude of the vectors and a counter-clockwise bias when determining the average direction of a vector field. We completed an additional study with two observers to try to uncover the source of the counter-clockwise bias. These results have direct implications to atmospheric scientists, but may also be able to be applied to other fields that use 2D vector fields.
Centrality Based Visualization of Small World Graphs
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Ham, Frank van; Wattenberg, Martin; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Current graph drawing algorithms enable the creation of two dimensional node-link diagrams of huge graphs. However, for graphs with low diameter (of which "small world" graphs are a subset) these techniques begin to break down visually even when the graph has only a few hundred nodes. Typical algorithms produce images where nodes clump together in the center of the screen, making it hard to discern structure and follow paths. This paper describes a solution to this problem, which uses a global edge metric to determine a subset of edges that capture the graph's intrinsic clustering structure. This structure is then used to create an embedding of the graph, after which the remaining edges are added back in. We demonstrate applications of this technique to a number of real world examples.
Interactive Exploratory Visualization of 2D Vector Fields
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Isenberg, Tobias; Everts, Maarten H.; Grubert, Jens; Carpendale, Sheelagh; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
In this paper we present several techniques to interactively explore representations of 2D vector fields. Through a set of simple hand postures used on large, touch-sensitive displays, our approach allows individuals to customdesign glyphs (arrows, lines, etc.) that best reveal patterns of the underlying dataset. Interactive exploration of vector fields is facilitated through freedom of glyph placement, glyph density control, and animation. The custom glyphs can be applied individually to probe specific areas of the data but can also be applied in groups to explore larger regions of a vector field. Re-positionable sources from which glyphs - animated according to the local vector field - continue to emerge are used to examine the vector field dynamically. The combination of these techniques results in an engaging visualization with which the user can rapidly explore and analyze varying types of 2D vector fields, using a virtually infinite number of custom-designed glyphs.
Lagrangian Visualization of Flow-Embedded Surface Structures
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Garth, Christoph; Wiebel, Alexander; Tricoche, Xavier; Joy, Ken; Scheuermann, Gerik; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
The notions of Finite-Time Lyapunov Exponent (FTLE) and Lagrangian Coherent Structures provide a strong framework for the analysis and visualization of complex technical flows. Their definition is simple and intuitive, and they are built on a deep theoretical foundation. We apply these concepts to enable the analysis of flows in the immediate vicinity of the boundaries of flow-embedded objects by limiting the Lagrangian analysis to surfaces closely neighboring these boundaries. To this purpose, we present an approach to approximate FTLE fields over such surfaces. Furthermore, we achieve an effective depiction of boundary-related flow structures such as separation and attachment over object boundaries and specific insight into the surrounding flow using several specifically chosen visualization techniques. We document the applicability of our methods by presenting a number of application examples.
Evaluation of Illustration-inspired Techniques for Time-varying Data Visualization
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Joshi, Alark; Rheingans, Penny; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Illustration-inspired techniques have provided alternative ways to visualize time-varying data. Techniques such as speedlines, flow ribbons, strobe silhouettes and opacity-based techniques provide temporal context to the current timestep being visualized. We evaluated the effectiveness of these illustrative techniques by conducting a user study. We compared the ability of subjects to visually track features using snapshots, snapshots augmented by illustration techniques, animations, and animations augmented by illustration techniques. User accuracy, time required to perform a task, and user confidence were used as measures to evaluate the techniques. The results indicate that the use of illustration-inspired techniques provides a significant improvement in user accuracy and the time required to complete the task. Subjects performed significantly better on each metric when using augmented animations as compared to augmented snapshots.
Discrete Multi-Material Interface Reconstruction for Volume Fraction Data
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Anderson, John C.; Garth, C.; Duchaineau, Mark A.; Joy, Kenneth I.; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
We present the results from a user study looking at the ability of observers to mentally integrate wind direction and magnitude over a vector field. The data set chosen for the study is an MM5 (PSU/NCAR Mesoscale Model) simulation of Hurricane Lili over the Gulf of Mexico as it approaches the southeastern United States. Nine observers participated in the study. This study investigates the effect of layering on the observer's ability to determine the magnitude and direction of a vector field. We found a tendency for observers to underestimate the magnitude of the vectors and a counter-clockwise bias when determining the average direction of a vector field. We completed an additional study with two observers to try to uncover the source of the counter-clockwise bias. These results have direct implications to atmospheric scientists, but may also be able to be applied to other fields that use 2D vector fields.
A Screen Space Quality Method for Data Abstraction
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Johansson, Jimmy; Cooper, Matthew; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
The rendering of large data sets can result in cluttered displays and non-interactive update rates, leading to time consuming analyses. A straightforward solution is to reduce the number of items, thereby producing an abstraction of the data set. For the visual analysis to remain accurate, the graphical representation of the abstraction must preserve the significant features present in the original data. This paper presents a screen space quality method, based on distance transforms, that measures the visual quality of a data abstraction. This screen space measure is shown to better capture significant visual structures in data, compared with data space measures. The presented method is implemented on the GPU, allowing interactive creation of high quality graphical representations of multivariate data sets containing tens of thousands of items
Illustrative Parallel Coordinates
(The Eurographics Association and Blackwell Publishing Ltd., 2008) McDonnell, Kevin T.; Mueller, Klaus; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Illustrative parallel coordinates (IPC) is a suite of artistic rendering techniques for augmenting and improving parallel coordinate (PC) visualizations. IPC techniques can be used to convey a large amount of information about a multidimensional dataset in a small area of the screen through the following approaches: (a) edge-bundling through splines; (b) visualization of "branched" clusters to reveal the distribution of the data; (c) opacity-based hints to show cluster density; (d) opacity and shading effects to illustrate local line density on the parallel axes; and (e) silhouettes, shadows and halos to help the eye distinguish between overlapping clusters. Thus, the primary goal of this work is to convey as much information as possible in a manner that is aesthetically pleasing and easy to understand for non-experts.
Topology-Preserving lambda_2-based Vortex Core Line Detection for Flow Visualization
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Schafhitzel, Tobias; Vollrath, Joachim E.; Gois, Joao P.; Weiskopf, Daniel; Castelo, Antonio; Ertl, Thomas; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
We propose a novel vortex core line extraction method based on the lambda_2 vortex region criterion in order to improve the detection of vortex features for 3D flow visualization. The core line is defined as a curve that connects lambda_2 minima restricted to planes that are perpendicular to the core line. The basic algorithm consists of the following stages: (1) lambda_2 field construction and isosurface extraction; (2) computation of the curve skeleton of the lambda_2 isosurface to build an initial prediction for the core line; (3) correction of the locations of the prediction by searching for lambda_2 minima on planes perpendicular to the core line. In particular, we consider the topology of the vortex core lines, guaranteeing the same topology as the initial curve skeleton. Furthermore, we propose a geometry-guided definition of vortex bifurcation, which represents the split of one core line into two parts. Finally, we introduce a user-guided approach in order to narrow down vortical regions taking into account the graph of lambda_2 along the computed vortex core line. We demonstrate the effectiveness of our method by comparing our results to previous core line detection methods with both simulated and experimental data; in particular, we show robustness of our method for noise-affected data.
Visual Clustering in Parallel Coordinates
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Zhou, Hong; Yuan, Xiaoru; Qu, Huamin; Cui, Weiwei; Chen, Baoquan; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Parallel coordinates have been widely applied to visualize high-dimensional and multivariate data, discerning patterns within the data through visual clustering. However, the effectiveness of this technique on large data is reduced by edge clutter. In this paper, we present a novel framework to reduce edge clutter, consequently improving the effectiveness of visual clustering. We exploit curved edges and optimize the arrangement of these curved edges by minimizing their curvature and maximizing the parallelism of adjacent edges. The overall visual clustering is improved by adjusting the shape of the edges while keeping their relative order. The experiments on several representative datasets demonstrate the effectiveness of our approach.
Interactive Visualization of Multimodal Volume Data for Neurosurgical Tumor Treatment
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Rieder, Christian; Ritter, Felix; Raspe, Matthias; Peitgen, Heinz-Otto; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
We present novel interactive methods for the visualization of multimodal volume data as used in neurosurgical therapy planning. These methods allow surgeons to explore multimodal volumes and focus on functional data and lesions. Computer graphics techniques are proposed to create expressive visualizations at interactive frame rates to reduce time-consuming and complex interaction with the medical data. Contributions of our work are the distance-based enhancements of functional data and lesions which allows the surgeon to perceive functional and anatomical structures at once and relate them directly to the intervention. In addition we propose methods for the visual exploration of the path to the structures of interest, to enhance anatomical landmarks, and to provide additional depth indicators. These techniques have been integrated in a visualization prototype that provides interaction capabilities for finding the optimal therapeutic strategy for the neurosurgeon.
Virtual Klingler Dissection: Putting Fibers into Context
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Schultz, Thomas; Sauber, Natascha; Anwander, Alfred; Theisel, Holger; Seidel, Hans-Peter; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Fiber tracking is a standard tool to estimate the course of major white matter tracts from diffusion tensor magnetic resonance imaging (DT-MRI) data. In this work, we aim at supporting the visual analysis of classical streamlines from fiber tracking by integrating context from anatomical data, acquired by a T1-weighted MRI measurement. To this end, we suggest a novel visualization metaphor, which is based on data-driven deformation of geometry and has been inspired by a technique for anatomical fiber preparation known as Klingler dissection. We demonstrate that our method conveys the relation between streamlines and surrounding anatomical features more effectively than standard techniques like slice images and direct volume rendering. The method works automatically, but its GPU-based implementation allows for additional, intuitive interaction.
Abstractive Representation and Exploration of Hierarchically Clustered Diffusion Tensor Fiber Tracts
(The Eurographics Association and Blackwell Publishing Ltd., 2008) Chen, Wei; Zhang, Song; Correia, Stephen; Ebert, David S.; A. Vilanova, A. Telea, G. Scheuermann, and T. Moeller
Diffusion tensor imaging (DTI) has been used to generate fibrous structures in both brain white matter and muscles. Fiber clustering groups the DTI fibers into spatially and anatomically related tracts. As an increasing number of fiber clustering methods have been recently developed, it is important to display, compare, and explore the clustering results efficiently and effectively. In this paper, we present an anatomical visualization technique that reduces the geometric complexity of the fiber tracts and emphasizes the high-level structures. Beginning with a volumetric diffusion tensor image, we first construct a hierarchical clustering representation of the fiber bundles. These bundles are then reformulated into a 3D multi-valued volume data. We then build a set of geometric hulls and principal fibers to approximate the shape and orientation of each fiber bundle. By simultaneously visualizing the geometric hulls, individual fibers, and other data sets such as fractional anisotropy, the overall shape of the fiber tracts are highlighted, while preserving the fibrous details. A rater with expert knowledge of white matter structure has evaluated the resulting interactive illustration and confirmed the improvement over straightforward DTI fiber tract visualization.

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