EuroVis05: Joint Eurographics - IEEE VGTC Symposium on Visualization

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https://diglib.eg.org/handle/10.2312/400

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Spline-Based Gradient Filters For High-Quality Refraction Computations in Discrete Datasets
(The Eurographics Association, 2005) Li, Shengying; Mueller, Klaus; Ken Brodlie and David Duke and Ken Joy
Based on the finding that refraction imposes significantly higher demands onto gradient filters than illumination and shading, we evaluate the family of spline filters as a good alternative to the cubic filters, which so far have served as the gold standard of efficient yet high-quality interpolation filters in present visualization applications. Using a regular background texture to visualize the refractive properties of the volumetric object, we also describe an efficient scheme to achieve the effects of supersampling without incurring any extra raycasting overhead. Our results indicate that splines can be superior to the Catmull-Rom filter, with potentially less computational overhead, also offering a convenient means to adjust the extent of lowpassing and smoothing.
Illustrative Context-Preserving Volume Rendering
(The Eurographics Association, 2005) Bruckner, Stefan; Grimm, Sören; Kanitsar, Armin; Gröller, M. Eduard; Ken Brodlie and David Duke and Ken Joy
In volume rendering it is very difficult to simultaneously visualize interior and exterior structures while preserving clear shape cues. Very transparent transfer functions produce cluttered images with many overlapping structures, while clipping techniques completely remove possibly important context information. In this paper we present a new model for volume rendering, inspired by techniques from illustration that provides a means of interactively inspecting the interior of a volumetric data set in a feature-driven way which retains context information. The context-preserving volume rendering model uses a function of shading intensity, gradient magnitude, distance to the eye point, and previously accumulated opacity to selectively reduce the opacity in less important data regions. It is controlled by two user-specified parameters. This new method represents an alternative to conventional clipping techniques, shares their easy and intuitive user control, but does not suffer from the drawback of missing context information.
Galilean Invariant Extraction and Iconic Representation of Vortex Core Lines
(The Eurographics Association, 2005) Sahner, Jan; Weinkauf, Tino; Hege, Hans-Christian; Ken Brodlie and David Duke and Ken Joy
While vortex region quantities are Galilean invariant, most methods for extracting vortex cores depend on the frame of reference. We present an approach to extracting vortex core lines independently of the frame of reference by extracting ridge and valley lines of Galilean invariant vortex region quantities. We discuss a generalization of this concept leading to higher dimensional features. For the visualization of extracted line features we use an iconic representation indicating their scale and extent. We apply our approach to datasets from numerical simulations and experimental measurements.
Real-Time Advection and Volumetric Illumination for the Visualization of 3D Unsteady Flow
(The Eurographics Association, 2005) Weiskopf, Daniel; Schafhitzel, Tobias; Ertl, Thomas; Ken Brodlie and David Duke and Ken Joy
This paper presents an interactive technique for the dense texture-based visualization of unsteady 3D flow, taking into account issues of computational efficiency and visual perception. High efficiency is achieved by a novel 3D GPU-based texture advection mechanism that implements logical 3D grid structures by physical memory in the form of 2D textures. This approach results in fast read and write access to physical memory, independent of GPU architecture. Slice-based direct volume rendering is used for the final display. A real-time computation of gradients is employed to achieve volume illumination. Perception-guided volume shading methods are included, such as halos, cool/warm shading, or color-based depth cueing. The problems of clutter and occlusion are addressed by supporting a volumetric importance function that enhances features of the flow and reduces visual complexity in less interesting regions.
Localized Flow Analysis of 2D and 3D Vector Fields
(The Eurographics Association, 2005) Wiebel, Alexander; Garth, Christoph; Scheuermann, Gerik; Ken Brodlie and David Duke and Ken Joy
In this paper we present an approach to the analysis of the contribution of a small subregion in a dataset to the global flow. To this purpose, we subtract the potential flow that is induced by the boundary of the sub-domain from the original flow. Since the potential flow is free of both divergence and rotation, the localized flow field retains the original features. In contrast to similar approaches, by making explicit use of the boundary flow of the subregion, we manage to isolate the region-specific flow that contains exactly the local contribution of the considered subdomain to the global flow. In the remainder of the paper, we describe an implementation on unstructured grids in both two and three dimensions. We discuss the application of several widely used feature extraction methods on the localized flow, with an emphasis on topological schemes.
VIS-a-VE: Visual Augmentation for Virtual Environments in Surgical Training
(The Eurographics Association, 2005) Chung, Adrian; Deligianni, Fani; Shah, Pallav; Wells, Athol; Yang, Guang-Zhong; Ken Brodlie and David Duke and Ken Joy
Photo-realistic rendering combined with vision techniques is an important trend in developing next generation surgical simulation devices. Training with simulator is generally low in cost and more efficient than traditional methods that involve supervised learning on actual patients. Incorporating genuine patient data in the simulation can significantly improve the efficacy of training and skills assessment. In this paper, a photo-realistic simulation architecture is described that utilises patient-specific models for training in minimally invasive surgery. The datasets are constructed by combining computer tomographic images with bronchoscopy video of the same patient so that the three dimensional structures and visual appearance are accurately matched. Using simulators enriched by a library of datasets with sufficient patient variability, trainees can experience a wide range of realistic scenarios, including rare pathologies, with correct visual information. In this paper, the matching of CT and video data is accomplished by using a newly developed 2D/3D registration method that exploits a shape from shading similarity measure. Additionally, a method has been devised to allow shading parameter estimation by modelling the bidirectional reflectance distribution function (BRDF) of the visible surfaces. The derived BRDF is then used to predict the expected shading intensity such that a texture map independent of lighting conditions can be extracted. Thus new views can be generated that were not captured in the original bronchoscopy video, thus allowing free navigation of the acquired 3D model with enhanced photo-realism.
Analysis and Visualization of 3-C PIV Images from HART II using Image Processing Methods
(The Eurographics Association, 2005) Ebling, Julia; Scheuermann, Gerik; Wall, Berend G. van der; Ken Brodlie and David Duke and Ken Joy
In this paper, three-component particle image velocimetry (3-C PIV) measurements within the wake of a helicopter rotor from the HART II test are analyzed. These PIV-images are quite a challenge as the noise due to the measurement method and the inherent turbulence of the flow can not be distinguished. Furthermore, features are often hidden by a mean flow, which is influenced by vortices and therefore not easy to determine. The authors present some image processing methods adapted to these vector fields for the computation of position, size, and direction of the vortices in this data. These methods are quite robust in terms of noise and independent of any mean flow and therefore appropriate for this analysis. The results of the analysis allow a more descriptive and intuitive visualization of the vortices.
Interactive Methods for Exploring Particle Simulation Data
(The Eurographics Association, 2005) Co, Christopher S.; Friedman, Alex; Grote, David P.; Vay, Jean-Luc; Bethel, E. Wes; Joy, Kenneth I.; Ken Brodlie and David Duke and Ken Joy
In this work, we visualize high-dimensional particle simulation data using a suite of scatterplot-based visualizations coupled with interactive selection tools. We use traditional 2D and 3D projection scatterplots as well as a novel oriented-disk rendering style to convey various information about the data. Interactive selection tools allow physicists to manually classify "interesting" sets of particles that are highlighted across multiple, linked views of the data. The power of our application is the ability to correspond new visual representations of the simulation data with traditional, well understood visualizations. This approach supports the interactive exploration of the high-dimensional space while promoting discovery of new particle behavior.
Interactive Visualization for Neck-Dissection Planning
(The Eurographics Association, 2005) Krüger, Arno; Tietjen, Christian; Hintze, Jana; Preim, Bernhard; Hertel, Ilka; Strauß, Gero; Ken Brodlie and David Duke and Ken Joy
In this paper, we present visualization techniques for neck dissection planning. These interventions are carried out to remove lymph node metastasis in the neck region. 3d visualization is intended to explore and to quantify anatomic and pathologic structures and thus support decisions concerning the surgical strategy. For this purpose we developed and combined visualization and interaction techniques such as cutaway views, silhouettes and colorcoded distances. In addition, a standardized procedure for processing and visualization of the patient data is presented.
Tiled Parallel Coordinates for the Visualization of Time-Varying Multichannel EEG Data
(The Eurographics Association, 2005) Caat, Michael ten; Maurits, N. M.; Roerdink, J. B. T. M.; Ken Brodlie and David Duke and Ken Joy
The field of visualization assists data interpretation in many areas, but some types of data are not manageable by existing visualization techniques. This holds in particular for time-varying multichannel EEG data. No existing technique can simultaneously visualize information from all channels in use and all time steps. To address this problem, a new visualization technique is presented, based on the parallel coordinate method and making use of a tiled organization. This tiled organization employs a two-dimensional row-column representation, rather than a one-dimensional arrangement in columns as used for the classical parallel coordinates. The usefulness of the new method, referred to as tiled parallel coordinates, is demonstrated by one particular type of EEG data. It can be applied to an arbitrary number of time steps, for the maximum number of channels currently in use. The general setup of the method makes it widely applicable to other time-varying multivariate data types.
GVis: A Scalable Visualization Framework for Genomic Data
(The Eurographics Association, 2005) Hong, Jin; Jeong, Dong Hyun; Shaw, Chris D; Ribarsky, William; Borodovsky, Mark; Song, Chang; Ken Brodlie and David Duke and Ken Joy
This paper describes a framework we have developed for the visual analysis of large-scale phylogeny hierarchies populated with the genomic data of various organisms. This framework allows the user to quickly browse the phylogeny hierarchy of organisms from the highest level down to the level of an individual genome for the desired organism of interest. Based on this framework, the user can initiate gene-finding and gene-matching analyses and view the resulting annotated coding potential graphs in the same multi-scale visualization framework, permitting correlative analysis and further investigation. This paper introduces our framework and describes the data structures and algorithms that support it.
Hardware-Accelerated Glyphs for Mono- and Dipoles in Molecular Dynamics Visualization
(The Eurographics Association, 2005) Reina, Guido; Ertl, Thomas; Ken Brodlie and David Duke and Ken Joy
We present a novel visualization method for mono- and dipolar molecular simulations from thermodynamics that takes advantage of modern graphics hardware to interactively render specifically tailored glyphs. Our approach allows domain experts to visualize the results of molecular dynamics simulations with a higher number of particles than before and furthermore offers much better visual quality. We achieve this by transferring only visualization parameters to the GPU and by generating implicit surfaces directly in the fragment program. As a result, we can render up to 500.000 glyphs with about 10 fps displaying all the simulation results as geometrical properties that resemble the classical abstract representation used in this research area. Thus we enable researchers to visually assess the results of simulations of greater scale than before. We believe that the proposed method can be generalized to create other kinds of parametrized surfaces directly on graphics hardware to overcome the bandwidth bottleneck that exists between CPU and GPU.
High-Quality Volume Rendering with Resampling in the Frequency Domain
(The Eurographics Association, 2005) Artner, Martin; Möller, Torsten; Viola, Ivan; Gröller, Meister E.; Ken Brodlie and David Duke and Ken Joy
This work introduces a volume rendering technique that is conceptually based on the shear-warp factorization. We propose to perform the shear transformation in the frequency domain. Unlike the standard shear-warp algorithm, we allow for arbitrary sampling distances along the viewing rays, independent from the view direction. The accurate scaling of the volume slices is achieved by using the zero padding interpolation property. Finally, a high quality gradient estimation scheme is presented which uses the derivative theorem of the Fourier transform. Experimental results show that the presented method outperforms established algorithms in the quality of the produced images. If the data is sampled above the Nyquist rate the presented method is capable of a perfect reconstruction of the original function.
Scalable, Robust Visualization of Very Large Trees
(The Eurographics Association, 2005) Beermann, Dale; Munzner, Tamara; Humphreys, Greg; Ken Brodlie and David Duke and Ken Joy
The TreeJuxtaposer system [MGT*03] allowed visual comparison of large trees with guaranteed visibility of landmarks and Focus+Context navigation. While that system allowed exploration and comparison of larger datasets than previous work, it was limited to a single tree of 775,000 nodes by a large memory footprint. In this paper, we describe the theoretical limitations to TreeJuxtaposer's architecture that severely restrict its scalability. We provide two scalable, robust solutions to these limitations: TJC and TJC-Q. TJC is a system that supports browsing trees up to 15 million nodes by exploiting leading-edge graphics hardware while TJC-Q allows browsing trees up to 5 million nodes on commodity platforms. Both of these systems use a fast new algorithm for drawing and culling and benefit from a complete redesign of all data structures for more efficient memory usage and reduced preprocessing time.
BioBrowser: A Framework for Fast Protein Visualization
(The Eurographics Association, 2005) Halm, Andreas; Offen, Lars; Fellner, Dieter W.; Ken Brodlie and David Duke and Ken Joy
This paper presents a protein visualization system called BioBrowser, which provides high quality images at interactive frame rates for molecules of extreme size and complexity. This is achieved by a shift in the tessellation approach: triangle meshes are not produced a priori on a 'just-in-case' basis. Instead, tessellation happens 'justin- time' given a certain camera position, image size and interaction demand. Thus, our approach is based on multiresolution meshes and on new extensions of graphics hardware. The paper shows how to reduce geometric data by using subdivision surfaces for ribbon structures and molecular surfaces and by using billboards instead of spheres consisting of triangles. It also shows how to use fragment shaders to create a three dimensional appearance and realistic sphere intersections. The combination of these approaches leads to an image quality not yet seen in interactive visualization environments for molecules of that size/complexity. All the above methods are combined to gain a high performance configurable visualization system on standard hardware.
Vector Field Analysis and Visualization through Variational Clustering
(The Eurographics Association, 2005) McKenzie, Alexander; Lombeyda, Santiago V.; Desbrun, Mathieu; Ken Brodlie and David Duke and Ken Joy
Scientific computing is an increasingly crucial component of research in various disciplines. Despite its potential, exploration of the results is an often laborious task, owing to excessively large and verbose datasets output by typical simulation runs. Several approaches have been proposed to analyze, classify, and simplify such data to facilitate an informative visualization and deeper understanding of the underlying system. However, traditional methods leave much room for improvement. In this article we investigate the visualization of large vector fields, departing from accustomed processing algorithms by casting vector field simplification as a variational partitioning problem. Adopting an iterative strategy, we introduce the notion of vector "proxies" to minimize the distortion error of our simplification by clustering the dataset into multiple best-fitting characteristic regions. This error driven approach can be performed with respect to various similarity metrics, offering a convenient set of tools to design clear and succinct representations of high dimensional datasets. We illustrate the bene fits of such tools through visualization experiments of three-dimensional vector fields.
Non-manifold Mesh Extraction from Time-varying Segmented Volumes used for Modeling a Human Heart
(The Eurographics Association, 2005) Bertram, Martin; Reis, Gerd; Lengen, Rolf H. van; Köhn, Sascha; Hagen, Hans; Ken Brodlie and David Duke and Ken Joy
We present a new algorithm extracting and fairing surfaces from segmented volumes composed of multiple materials. In a first pass, the material boundaries in the volume are smoothed considering signed distance functions for the individual materials. Second, we apply a marching-cubes-like contouring method providing initial meshes defining material boundaries. Non-manifold features emerge along lines where more than two materials encounter. Finally, the mesh geometry is relaxed in a constrained fairing process. We use our algorithm to construct a heart model from segmented time-varying magnetic resonance images. Information concerning the heart ontology is used to merge certain structures to functional units.
Visualization for Validation and Improvement of Three-dimensional Segmentation Algorithms
(The Eurographics Association, 2005) Weber, Gunther H.; Hendriks, Cris L. Luengo; Keränen, Soile V. E.; Dillard, Scott E.; Ju, Derek Y.; Sudar, Damir; Hamann, Bernd; Ken Brodlie and David Duke and Ken Joy
The Berkeley DrosophilaTranscription Network Project (BDTNP) is developing a suite of methods that will allow a quantitative description and analysis of three dimensional (3D) gene expression patterns in an animal with cel- lular resolution. An important component of this approach are algorithms that segment 3D images of an organism into individual nuclei and cells and measure relative levels of gene expression. As part of the BDTNP, we are devel- oping tools for interactive visualization, control, and verification of these algorithms. Here we present a volume visualization prototype system that, combined with user interaction tools, supports validation and quantitative determination of the accuracy of nuclear segmentation. Visualizations of nuclei are combined with information obtained from a nuclear segmentation mask, supporting the comparison of raw data and its segmentation. It is possible to select individual nuclei interactively in a volume rendered image and identify incorrectly segmented objects. Integration with segmentation algorithms, implemented in MATLAB, makes it possible to modify a segmentation based on visual examination and obtain additional information about incorrectly segmented objects. This work has already led to significant improvements in segmentation accuracy and opens the way to enhanced analysis of images of complex animal morphologies.
Isosurface Extraction Using Fixed-Sized Buckets
(The Eurographics Association, 2005) Waters, Kenneth W.; Co, Christopher S.; Joy, Kenneth I.; Ken Brodlie and David Duke and Ken Joy
We present a simple and output optimal algorithm for accelerated isosurface extraction from volumetric data sets. Output optimal extraction algorithms perform an amount of work dominated by the size of the (output) isosurface rather than the size of the (input) data set. While several optimal methods have been proposed to accelerate isosurface extraction, these algorithms are relatively complicated to implement or require quantized values as input. Our method is based on a straightforward array data structure that only requires an auxiliary sorting routine for construction. The method works equally well for floating point data as it does for quantized data sets. We demonstrate how the data structure can exploit coherence between isosurfaces by performing searches incrementally. We show results for real application data validating the method's optimality.
Mail Explorer - Spatial and Temporal Exploration of Electronic Mail
(The Eurographics Association, 2005) Keim, Daniel A.; Mansmann, Florian; Panse, Christian; Schneidewind, Jörn; Sips, Mike; Ken Brodlie and David Duke and Ken Joy
In today s world, e-mail has become one of the most important means of communication in business and private lives due to its efficiency. However, the problems start as soon as mail volumes go beyond the scope of human information processing capabilities. Firstly, time does not allow for leaving certain messages unanswered for a long time, and in certain cases, for reading all messages. Secondly, the dilemma of electronic filters leaves a choice of too many junk mails getting through versus a risk of solicited mails being dumped. In this paper we present a new interactive visual data mining approach for analyzing individual e-mail communication. It combines classical visual analytics (help to identify pattern such as peaks and trends over time) with geo-spatial map distortions (help to understand the routes of e-mails). Experiments show that our visual e-mail explorer produces useful and interesting visualizations of large collections of e-mail and is practical for exploring temporal and geo-spatial patterns hidden in the e-mail data.

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