DevLan/vispubs huggingface dataset:
Isosurfaces on Optimal Regular Samples
Authors: Hamish A. Carr, Thomas Theußl, Torsten Möller
Published at EuroVis, 2003

Volumetric samples on Cartesian lattices are less efficient than samples on body-centred cubic (BCC) lattices. We show how to construct isosurfaces on BCC lattices using several different algorithms. Since the mesh that arises from BCC lattices involves a large number of cells, we show two alternate methods of reducing the number of cells by clumping tetrahedra into either octahedra or hexahedra. We also propose a theoretical model for estimating triangle counts for various algorithms, and present experimental results to show that isosurfaces generated using one of our algorithms can be competitive with isosurfaces generated using Marching Cubes on similar Cartesian grids.
MCMR: A Fluid View on Time Dependent Volume Data
Authors: Wim C. de Leeuw, Robert van Liere
Published at EuroVis, 2003

Mass Conservative Motion Reconstruction is a new method for estimating motion in time dependent volume data. A time dependent vector field representing the movement of the data is computed from a sequence of scalar volume data sets. The principle of mass conservation in a continuum is used during the reconstruction. Standard fiow visualization techniques are used for the visualization of the derived vector field.This paper presents the underlying concepts of MCMR, its implementation, its accuracy and applicability.
Path Seeds and Flexible Isosurfaces - Using Topology for Exploratory Visualization
Authors: Hamish A. Carr, Jack Snoeyink
Published at EuroVis, 2003

Morse theory and the Reeb graph give topological summaries of the behaviour of continuous scalar functions. The contour tree augments the Reeb graph for the isosurfaces in a volume to store seed sets, which are starting points for extracting isosurfaces by the continuation method. We replace the minimal seed sets of van Kreveld et al. with path seeds, which generate paths that correspond directly to the individual components of an isosurface. From a path we get exactly one seed per component, which reduces storage and simplifies isosurface extraction. Moreover, the correspondence allows us to extend the contour spectrum of Bajaj et al. to an interface that we call flexible isosurfaces, in which individual contours with different isovalues can be displayed, manipulated and annotated. The largest contour segmentation, in which separate surfaces are generated for each local maximum of the field, is a special case of the flexible isosurface.
Post-convolved Splatting
Authors: Neophytos Neophytou, Klaus Mueller 0001
Published at EuroVis, 2003

One of the most expensive operations in volume rendering is the interpolation of samples in volume space. The number of samples, in turn, depends on the resolution of the final image. Hence, viewing the volume at high magnification will incur heavy computation. In this paper, we explore an approach that limits the number of samples to the resolution of the volume, independent of the magnification factor, using a cheap post-convolution process on the interpolated samples to generate the missing samples. For X-ray, this post-convolution is needed only once, after the volume is fully projected, while in full volume rendering, the post-convolution must be applied before each shading and compositing step. Using this technique, we are able to achieve speedups of two and more, without compromising rendering quality. We demonstrate our approach using an image-aligned sheet-buffered splatting algorithm, but our conclusions readily generalize to any volume rendering algorithm that advances across the volume in a slice-based fashion.
Rendering Vector Data over Global, Multiresolution 3D Terrain
Authors: Zachary Wartell, Eunjung Kang, Tony Wasilewski, William Ribarsky, Nickolas Faust
Published at EuroVis, 2003

Modern desktop PCs are capable of taking 2D Geographic Information System (GIS) applications into the realm of interactive 3D virtual worlds. In prior work we developed and presented graphics algorithms and data management methods for interactive viewing of a 3D global terrain system for desktop and virtual reality systems. In this paper we present a key data structure and associated render-time algorithm for the combined display of multi-resolution 3D terrain and traditional GIS polyline vector data. Such vector data is traditionally used for representing geographic entities such as political borders, roads, rivers and cadastral information.
ShellSplatting: Interactive Rendering of Anisotropic Volumes
Authors: Charl P. Botha, Frits H. Post
Published at EuroVis, 2003

This work presents an extension of shell rendering that is moreflexible and yields higher quality volume renderings. Shell rendering consists of efficient data-structures and methods to manipulate and render structures with non-precise boundaries in volume data. We have updated these algorithms by creating an implementation that makes effective use of ubiquitously available commercial graphics hardware. More significantly, we have extended the algorithm to make use of elliptical Gaussian splats instead of straight-forward voxel projection. This dramatically increases the quality of the renderings, especially with anisotropically sampled volumes. The use of the graphics hardware alleviates the performance penalty of using splats.
Shrouds: Optimal Separating Surfaces for Enumerated Volumes
Authors: Gregory M. Nielson, Gary Graf, Ryan Holmes, Adam Huang, Mariano Phielipp
Published at EuroVis, 2003

We describe new techniques for computing a smooth triangular mesh surface that surrounds an enumerated volume consisting of a collection of points from a 3D rectilinear grid. The surface has the topology of an isosurface computed by a marching cubes method applied to a field function that has the value one at the points in the volume and zero for points not in the volume. The vertices are confined to the edges of the grid that penetrate this separating surface and the precise positions are computed so as to optimize a certain energy functional applied to the surface. We use efficient iterative methods to compute the optimal separating surfaces. We lift the concept of energy functionals for planar curves to isosurfaces by means of the 4*-network which is a unique collection of orthogonal planar polygons lying on the isosurface. The general strategy that we describe here leads to methods that are simple, efficient, and effective.
Smart Hardware-Accelerated Volume Rendering
Authors: Stefan Röttger, Stefan Guthe, Daniel Weiskopf, Thomas Ertl, Wolfgang Straßer
Published at EuroVis, 2003

For volume rendering of regular grids the display of view-plane aligned slices has proven to yield both good quality and performance. In this paper we demonstrate how to merge the most important extensions of the original 3D slicing approach, namely the pre-integration technique, volumetric clipping, and advanced lighting. Our approach allows the suppression of clipping artifacts and achieves high quality while offering the fiexibility to explore volume data sets interactively with arbitrary clip objects. We also outline how to utilize the proposed volumetric clipping approach for the display of segmented data sets. Moreover, we increase the rendering quality by implementing efficient over-sampling with the pixel shader of consumer graphics accelerators. We give prove that at least 4-times over-sampling is needed to reconstruct the ray integral with sufficient accuracy even with pre-integration. As an alternative to this brute-force over-sampling approach we propose a hardware-accelerated ray caster which is able to perform over-sampling only where needed and which is able to gain additional speed by early ray termination and space leaping.
Using Graphs for Fast Error Term Approximation of Time-varying Datasets
Authors: Christof Nuber, Eric LaMar, Valerio Pascucci, Bernd Hamann, Kenneth I. Joy
Published at EuroVis, 2003

We present a method for the efficient computation and storage of approximations of error tables used for error estimation of a region between different time steps in time-varying datasets. The error between two time steps is defined as the distance between the data of these time steps. Error tables are used to look up the error between different time steps of a time-varying dataset, especially when run time error computation is expensive. However, even the generation of error tables itself can be expensive. For n time steps, the exact error look-up table (which stores the error values for all pairs of time steps in a matrix) has a memory complexity and pre-processing time complexity of O(n2), and O(1) for error retrieval.Our approximate error look-up table approach uses trees, where the leaf nodes represent original time steps, and interior nodes contain an average (or best-representative) of the children nodes. The error computed on an edge of a tree describes the distance between the two nodes on that edge. Evaluating the error between two different time steps requires traversing a path between the two leaf nodes, and accumulating the errors on the traversed edges. For n time steps, this scheme has a memory complexity and pre-processing time complexity of O(n log(n)), a significant improvement over the exact scheme; the error retrieval complexity is O(log(n)). As we do not need to calculate all possible n2 error terms, our approach is a fast way to generate the approximation.
Vector field visualization using Markov Random Field texture synthesis
Authors: Francesca Taponecco, Marc Alexa
Published at EuroVis, 2003

Vector field visualization aims at generating images in order to convey the information existing in the data. We use Markov Random Field (MRF) texture synthesis methods to generate the visualization from a set of sample textures. MRF texture synthesis methods allow generating images that are locally similar to a given example image. We extend this idea for vector field visualization by identifying each vector value with a representative example image, e.g. a strongly directed texture that is rotated according to a 2D vector. The visualization is synthesized pixel by pixel, where each pixel is chosen from the sample texture according to the vector values of the local pixel. The visualization locally communicates the vector information as each pixel is chosen from a sample that is representative of the vector. Furthermore it is smooth, as MRF texture synthesis searches for best fitting neighborhoods. This leads to dense and smooth visualizations with the additional freedom to use arbitrary representation textures for any vector value.
Visual Hierarchical Dimension Reduction for Exploration of High Dimensional Datasets
Authors: Jing Yang 0001, Matthew O. Ward, Elke A. Rundensteiner, Shiping Huang
Published at EuroVis, 2003

Traditional visualization techniques for multidimensional data sets, such as parallel coordinates, glyphs, and scatterplot matrices, do not scale well to high numbers of dimensions. A common approach to solving this problem is dimensionality reduction. Existing dimensionality reduction techniques usually generate lower dimensional spaces that have little intuitive meaning to users and allow little user interaction. In this paper we propose a new approach to handling high dimensional data, named Visual Hierarchical Dimension Reduction (VHDR), that addresses these drawbacks. VHDR not only generates lower dimensional spaces that are meaningful to users, but also allows user interactions in most steps of the process. In VHDR, dimensions are grouped into a hierarchy, and lower dimensional spaces are constructed using clusters of the hierarchy. We have implemented the VHDR approach into XmdvTool, and extended several traditional multidimensional visualization methods to convey dimension cluster characteristics when visualizing the data set in lower dimensional spaces. Our case study of applying VHDR to a real data set supports our belief that this approach is effective in supporting the exploration of high dimensional data sets.
Visualizing Spatial Distribution Data Sets
Authors: Alison Luo, David L. Kao, Jennifer L. Dungan, Alex Pang
Published at EuroVis, 2003

In this paper, we define distributions as a new data type and address the challenges of visualizing spatial distribution data sets. Numerous visualization techniques exist today for dealing with scalar data. That is, there is a scalar value at each spatial location, which may also be changing over time. Likewise, techniques exist for dealing with vector, tensor and multivariate data sets. However, there is currently no systematic way of dealing with distribution data where there is a collection of values for the same variable at every location and time. Distribution data is increasingly becoming more common as computers and sensor technologies continue to improve. They have also been used in a number of fields ranging from agriculture, engineering design and manufacturing to weather forecasting. Rather than developing specialized visualization techniques for dealing with distribution data, the approach presented in this paper is to find a systematic way of extending existing visualization methods to handle this new data type. For example, we would like to be able to generate isosurfaces of 3D scalar distribution data sets, or generate streamlines of vector distribution data sets. In order to accomplish this goal, we propose the use of a set of mathematically and procedurally defined operators that allow us to work directly on distributions. Color images can also be found in www.cse.ucsc.edu/research/avis/operator.html.
Designing novel interactional workspaces to support face to face consultations
Authors: Tom Rodden, Yvonne Rogers, John Halloran 0001, Ian Taylor
Published at CHI, 2003

This paper describes the design and deployment of a novel interactional workspace, intended to provide more effective support for face-to-face consultations between two parties. We focus on the initial consultations between customer and agent that take place during the development of complex products. Findings from an ethnographic study of the existing use of technological systems show the interaction during such consultations to be disjointed and not well supported. As an alternative approach, we developed a novel arrangement of multiple displays intended to promote shoulder-to-shoulder collaboration using a variety of interlinked representations and visualizations. The resulting interactional workspace was used by a travel company as part of a large international trade show attended by the general public. The many consultations that took place between agents and customers were quite different, proving to be more equitable, open, fluid and congenial.
Halo: a technique for visualizing off-screen objects
Authors: Patrick Baudisch, Ruth Rosenholtz
Published at CHI, 2003

As users pan and zoom, display content can disappear into off-screen space, particularly on small-screen devices. The clipping of locations, such as relevant places on a map, can make spatial cognition tasks harder. Halo is a visualization technique that supports spatial cognition by showing users the location of off-screen objects. Halo accomplishes this by surrounding off-screen objects with rings that are just large enough to reach into the border region of the display window. From the portion of the ring that is visible on-screen, users can infer the off-screen location of the object at the center of the ring. We report the results of a user study comparing Halo with an arrow-based visualization technique with respect to four types of map-based route planning tasks. When using the Halo interface, users completed tasks 16-33% faster, while there were no significant differences in error rate for three out of four tasks in our study.
Recommending collaboration with social networks: a comparative evaluation
Authors: David W. McDonald
Published at CHI, 2003

Studies of information seeking and workplace collaboration often find that social relationships are a strong factor in determining who collaborates with whom. Social networks provide one means of visualizing existing and potential interaction in organizational settings. Groupware designers are using social networks to make systems more sensitive to social situations and guide users toward effective collaborations. Yet, the implications of embedding social networks in systems have not been systematically studied. This paper details an evaluation of two different social networks used in a system to recommend individuals for possible collaboration. The system matches people looking for expertise with individuals likely to have expertise. The effectiveness of social networks for matching individuals is evaluated and compared. One finding is that social networks embedded into systems do not match individuals' perceptions of their personal social network. This finding and others raise issues for the use of social networks in groupware. Based on the evaluation results, several design considerations are discussed.
Understanding sequence and reply relationships within email conversations: a mixed-model visualization
Authors: Gina Danielle Venolia, Carman Neustaedter
Published at CHI, 2003

It has been proposed that email clients could be improved if they presented messages grouped into conversations. An email conversation is the tree of related messages that arises from the use of the reply operation. We propose two models of conversation. The first model characterizes a conversation as a chronological sequence of messages; the second as a tree based on the reply relationship. We show how existing email clients and prior research projects implicitly support each model to a greater or lesser degree depending on their design, but none fully supports both models simultaneously. We present a mixed-model visualization that simultaneously presents sequence and reply relationships among the messages of a conversation, making both visible at a glance. We describe the integration of the visualization into a working prototype email client. A usability study indicates that the system meets our usability goals and verifies that the visualization fully conveys both types of relationships within the messages of an email conversation.
A case study in selective visualization of unsteady 3D flow
Authors: Dirk Bauer, Ronald Peikert, Mie Sato, Mirjam Sick
Published at Vis, 2002

In this case study, we explore techniques for the purpose of visualizing isolated flow structures in time-dependent data. Our primary industrial application is the visualization of the vortex rope, a rotating helical structure which builds up in the draft tube of a water turbine. The vortex rope can be characterized by high values of normalized helicity, which is a scalar field derived from the given CFD velocity data. In two related applications, the goal is to visualize the cavitation regions near the runner blades of a Kaplan turbine and a water pump, respectively. Again, the flow structure of interest can be defined by a scalar field, namely by low pressure values. We propose a particle seeding scheme based on quasi-random numbers, which minimizes visual artifacts such as clusters or patterns. By constraining the visualization to a region of interest, occlusion problems are reduced and storage efficiency is gained.
A case study on automatic camera placement and motion for visualizing historical data
Authors: Stanislav L. Stoev, Wolfgang Straßer
Published at Vis, 2002

In this paper, we address the problem of automatic camera positioning and automatic camera path generation in the context of historical data visualization. After short description of the given data, we elaborate on the constraints for the positioning of a virtual camera in such a way that not only the projected area is maximized, but also the depth of the displayed scene. This is especially important when displaying terrain models, which do not provide good 3D impression when only the projected area is maximized. Based on this concept, we present a method for computing an optimal camera position for each instant of time. Since the explored data are not static, but change depending on the explored scene time, we also discuss a method for animation generation. In order to avoid sudden changes of the camera position, when the previous method is applied for each frame (point in time), we introduce pseudo-events in time, which expand the bounding box defined by the currently active events of interest. In particular, this technique allows events happening in a future point in time to be taken into account such that when this time becomes current, all events of interest are already within the current viewing frustum of the camera.
A case study on multiresolution visualization of local rainfall from weather radar measurements
Authors: Thomas Gerstner, Dirk Meetschen, Susanne Crewell, Michael Griebel, Clemens Simmer
Published at Vis, 2002

Weather radars can measure the backscatter from rain drops in the atmosphere. A complete radar scan provides three-dimensional precipitation information. For the understanding of the underlying atmospheric processes interactive visualization of these data sets is necessary. This is a challenging task due to the size, structure and required context of the data. In this case study, a multiresolution approach for real-time simultaneous visualization of radar measurements together with the corresponding terrain data is illustrated.
A case study on the applications of a generic library for low-cost polychromatic passive stereo
Authors: Simon Stegmaier, Dirc Rose, Thomas Ertl
Published at Vis, 2002

Active stereo has been used by engineers and industrial designers for several years to enhance the perception of computer generated three-dimensional images. Unfortunately, active stereo requires specialized hardware. Therefore, as ubiquitous computing and teleworking gain importance, using active stereo becomes a problem. The goal of this case study is to examine the concept of a generic library for polychromatic passive stereo to make stereo vision available everywhere.
A model for the visualization exploration process
Authors: T. J. Jankun-Kelly, Kwan-Liu Ma, Michael Gertz 0001
Published at Vis, 2002

The current state of the art in visualization research places strong emphasis on different techniques to derive insight from disparate types of data. However, little work has investigated the visualization process itself. The information content of the visualization process - the results, history, and relationships between those results - is addressed by this work. A characterization of the visualization process is discussed, leading to a general model of the visualization exploration process. The model, based upon a new parameter derivation calculus, can be used for automated reporting, analysis, or visualized directly. An XML-based language for expressing visualization sessions using the model is also described. These sessions can then be shared and reused by collaborators. The model, along with the XML representation, provides an effective means to utilize information within the visualization process to further data exploration.
A multiphase approach to efficient surface simplification
Authors: Michael Garland, Eric Shaffer
Published at Vis, 2002

We present a new multiphase method for efficiently simplifying polygonal surface models of arbitrary size. It operates by combining an initial out-of-core uniform clustering phase with a subsequent in-core iterative edge contraction phase. These two phases are both driven by quadric error metrics, and quadrics are used to pass information about the original surface between phases. The result is a method that produces approximations of a quality comparable to quadric-based iterative edge contraction, but at a fraction of the cost in terms of running time and memory consumption.