DevLan/vispubs huggingface dataset:
Efficient computation of the topology of level sets
Authors: Valerio Pascucci, Kree Cole-McLaughlin
Published at Vis, 2002

This paper introduces two efficient algorithms that compute the Contour Tree of a 3D scalar field /spl Fscr/ and its augmented version with the Betti numbers of each isosurface. The Contour Tree is a fundamental data structure in scientific visualization that is used to preprocess the domain mesh to allow optimal computation of isosurfaces with minimal overhead storage. The Contour Tree can also be used to build user interfaces reporting the complete topological characterization of a scalar field. The first part of the paper presents a new scheme that augments the Contour Tree with the Betti numbers of each isocontour in linear time. We show how to extend the scheme with the Betti number computation without increasing its complexity. Thus, we improve on the time complexity from our previous approach from O(m log m) to O(n log n+m), where m is the number of tetrahedra and n is the number of vertices in the domain of /spl Fscr/. The second part of the paper introduces a new divide-and-conquer algorithm that computes the Augmented Contour Tree with improved efficiency. The central part of the scheme computes the output Contour Tree by merging two intermediate Contour Trees and is independent of the interpolant. In this way we confine any knowledge regarding a specific interpolant to an oracle that computes the tree for a single cell. We have implemented this oracle for the trilinear interpolant and plan to replace it with higher order interpolants when needed. The complexity of the scheme is O(n+t log n), where t is the number of critical points of /spl Fscr/. For the first time we can compute the Contour Tree in linear time in many practical cases when t=O(n/sup 1-/spl epsi//). Lastly, we report the running times for a parallel implementation of our algorithm, showing good scalability with the number of processors.
Efficient simplification of point-sampled surfaces
Authors: Mark Pauly, Markus H. Gross, Leif Kobbelt
Published at Vis, 2002

We introduce, analyze and quantitatively compare a number of surface simplification methods for point-sampled geometry. We have implemented incremental and hierarchical clustering, iterative simplification, and particle simulation algorithms to create approximations of point-based models with lower sampling density. All these methods work directly on the point cloud, requiring no intermediate tesselation. We show how local variation estimation and quadric error metrics can be employed to diminish the approximation error and concentrate more samples in regions of high curvature. To compare the quality of the simplified surfaces, we have designed a new method for computing numerical and visual error estimates for point-sampled surfaces. Our algorithms are fast, easy to implement, and create high-quality surface approximations, clearly demonstrating the effectiveness of point-based surface simplification.
Evaluation of a multimodal interface for 3D terrain visualization
Authors: David M. Krum, Olugbenga Omoteso, William Ribarsky, Thad Starner, Larry F. Hodges
Published at Vis, 2002

Novel speech and/or gesture interfaces are candidates for use in future mobile or ubiquitous applications. This paper describes an evaluation of various interfaces for visual navigation of a whole Earth 3D terrain model. A mouse driven interface, a speech interface, a gesture interface, and a multimodal speech and gesture interface were used to navigate to targets placed at various points on the Earth. This study measured each participant's recall of target identity, order, and location as a measure of cognitive load. Timing information as well as a variety of subjective measures including discomfort and user preference were taken. While the familiar and mature mouse interface scored best by most measures, the speech interface also performed well. The gesture and multimodal interface suffered from weaknesses in the gesture modality. Weaknesses in the speech and multimodal modalities are identified and areas for improvement are discussed.
Exploring scalar fields using critical isovalues
Authors: Gunther H. Weber, Gerik Scheuermann, Hans Hagen, Bernd Hamann
Published at Vis, 2002

Isosurfaces are commonly used to visualize scalar fields. Critical isovalues indicate isosurface topology changes: the creation of new surface components, merging of surface components or the formation of holes in a surface component. Therefore, they highlight interesting isosurface behavior and are helpful in exploration of large trivariate data sets. We present a method that detects critical isovalues in a scalar field defined by piecewise trilinear interpolation over a rectilinear grid and describe how to use them when examining volume data. We further review varieties of the marching cubes (MC) algorithm, with the intention of preserving topology of the trilinear interpolant when extracting an isosurface. We combine and extend two approaches in such a way that it is possible to extract meaningful isosurfaces even when a critical value is chosen as the isovalue.
Exploring surface characteristics with interactive Gaussian images (a case study)
Authors: Bradley C. Lowekamp, Penny Rheingans, Terry S. Yoo
Published at Vis, 2002

The Gauss map projects surface normals to a unit sphere, providing a powerful visualization of the geometry of a graphical object. it can be used to predict visual events caused by changes in lighting, shading, and camera control. We present an interactive technique for portraying the Gauss map of polygonal models, mapping surface normals and the magnitudes of surface curvature using a spherical projection. Unlike other visualizations of surface curvature, we create our Gauss map directly from polygonal meshes without requiring any complex intermediate calculations of differential geometry. For anything other than simple shapes, surface information is densely mapped into the Gaussian normal image, inviting the use of visualization techniques to amplify and emphasize details hidden within the wealth of data. We present the use of interactive visualization tools such as brushing and linking to explore the surface properties of solid shapes. The Gauss map is shown to be simple to compute, easy to view dynamically, and effective at portraying important features of polygonal models.
Face-based luminance matching for perceptual colormap generation
Authors: Gordon L. Kindlmann, Erik Reinhard, Sarah H. Creem-Regehr
Published at Vis, 2002

Most systems used for creating and displaying colormap-based visualizations are not photometrically calibrated. That is, the relationship between RGB input levels and perceived luminance is usually not known, due to variations in the monitor, hardware configuration, and the viewing environment. However, the luminance component of perceptually based colormaps should be controlled, due to the central role that luminance plays in our visual processing. We address this problem with a simple and effective method for performing luminance matching on an uncalibrated monitor. The method is akin to the minimally distinct border technique (a previous method of luminance matching used for measuring luminous efficiency), but our method relies on the brain's highly developed ability to distinguish human faces. We present a user study showing that our method produces equivalent results to the minimally distinct border technique, but with significantly improved precision. We demonstrate how results from our luminance matching method can be directly applied to create new univariate colormaps.
Fast and reliable space leaping for interactive volume rendering
Authors: Ming Wan, Aamir Sadiq, Arie E. Kaufman
Published at Vis, 2002

We present a fast and reliable space-leaping scheme to accelerate ray casting during interactive navigation in a complex volumetric scene, where we combine innovative space-leaping techniques in a number of ways. First, we derive most of the pixel depths at the current frame by exploiting the temporal coherence during navigation, where we employ a novel fast cell-based reprojection scheme that is more reliable than the traditional intersection-point based reprojection. Next, we exploit the object space coherence to quickly detect the remaining pixel depths, by using a precomputed accurate distance field that stores the Euclidean distance from each empty (background) voxel toward its nearest object boundary. In addition, we propose an effective solution to the challenging new-incoming-objects problem during navigation. Our algorithm has been implemented on a 16-processor SGI Power Challenge and reached interactive rendering rates at more than 10 Hz during the navigation inside 512/sup 3/ volume data sets acquired from both a simulation phantom and actual patients.
Fast view-dependent level-of-detail rendering using cached geometry
Authors: Joshua Levenberg
Published at Vis, 2002

Level-of-detail rendering is essential for rendering very large, detailed worlds in real-time. Unfortunately, level-of-detail computations can be expensive, creating a bottleneck at the CPU. This paper presents the CABTT algorithm, an extension to existing binary-triangle-tree-based level-of-detail algorithms. Instead of manipulating triangles, the CABTT algorithm instead operates on clusters of geometry called aggregate triangles. This reduces CPU overhead, eliminating a bottleneck common to level-of-detail algorithms. Since aggregate triangles stay fixed over several frames, they may be cached on the video card. This further reduces CPU load and fully utilizes the hardware accelerated rendering pipeline on modern video cards. These improvements result in a fourfold increase in frame rate over ROAM at high detail levels. Our implementation renders an approximation of an 8 million triangle height field at 42 frames per second with an maximum error of 1 pixel on consumer hardware.
Fast visualization of plane-like structures in voxel data
Authors: Steffen Prohaska, Hans-Christian Hege
Published at Vis, 2002

We present a robust, noise-resistant criterion characterizing plane-like skeletons in binary voxel objects. It is based on a distance map and the geodesic distance along the object's boundary. A parameter allows us to control the noise sensitivity. If needed, homotopy with the original object might be reconstructed in a second step, using an improved distance ordered thinning algorithm. The skeleton is analyzed to create a geometric representation for rendering. Plane-like parts are transformed into an triangulated surface not enclosing a volume by a suitable triangulation scheme. The resulting surfaces have lower triangle count than those created with standard methods and tend to maintain the original geometry, even after simplification with a high decimation rate. Our algorithm allows us to interactively render expressive images of complex 3D structures, emphasizing independently plane-like and rod-like structures. The methods are applied for visualization of the microstructure of bone biopsies.
GeneVis: visualization tools for genetic regulatory network dynamics
Authors: Charles A. H. Baker, Sheelagh Carpendale, Przemyslaw Prusinkiewicz, Michael G. Surette
Published at Vis, 2002

GeneVis provides a visual environment for exploring the dynamics of genetic regulatory networks. At present time, genetic regulation is the focus of intensive research worldwide, and computational aids are being called for to help in the research of factors that are difficult to observe directly. GeneVis provides a particle-based simulation of genetic networks and visualizes the process of this simulation as it occurs. Two dynamic visualization techniques are provided, a visualization of the movement of the regulatory proteins and a visualization of the relative concentrations of these proteins. Several interactive tools relate the dynamic visualizations to the underlying genetic network structure.
Geometric surface smoothing via anisotropic diffusion of normals
Authors: Tolga Tasdizen, Ross T. Whitaker, Paul Burchard, Stanley J. Osher
Published at Vis, 2002

This paper introduces a method for smoothing complex, noisy surfaces, while preserving (and enhancing) sharp, geometric features. It has two main advantages over previous approaches to feature preserving surface smoothing. First is the use of level set surface models, which allows us to process very complex shapes of arbitrary and changing topology. This generality makes it well suited for processing surfaces that are derived directly from measured data. The second advantage is that the proposed method derives from a well-founded formulation, which is a natural generalization of anisotropic diffusion, as used in image processing. This formulation is based on the proposition that the generalization of image filtering entails filtering the normals of the surface, rather than processing the positions of points on a mesh.
Geometric verification of swirling features in flow fields
Authors: Ming Jiang 0005, Raghu Machiraju, David S. Thompson
Published at Vis, 2002

In this paper, we present a verification algorithm for swirling features in flow fields, based on the geometry of streamlines. The features of interest in this case are vortices. Without a formal definition, existing detection algorithms lack the ability to accurately identify these features, and the current method for verifying the accuracy of their results is by human visual inspection. Our verification algorithm addresses this issue by automating the visual inspection process. It is based on identifying the swirling streamlines that surround the candidate vortex cores. We apply our algorithm to both numerically simulated and procedurally generated datasets to illustrate the efficacy of our approach.
Horizon occlusion culling for real-time rendering of hierarchical terrains
Authors: Brandon Lloyd, Parris K. Egbert
Published at Vis, 2002

We present a technique to perform occlusion culling for hierarchical terrains at run-time. The algorithm is simple to implement and requires minimal pre-processing and additional storage, yet leads to 2-4 times improvement in framerate for views with high degrees of occlusion. Our method is based on the well-known occlusion horizon algorithm. We show how to adapt the algorithm for use with hierarchical terrains. The occlusion horizon is constructed as the terrain is traversed in an approximate front to back ordering. Regions of the terrain are compared to the horizon to determine when they are completely occluded from the viewpoint. Culling these regions leads to significant savings in rendering.
Immersive volume visualization of seismic simulations: A case study of techniques invented and lessons learned
Authors: Prashant Chopra, Jörg Meyer 0003, Antonio Fernandez
Published at Vis, 2002

This paper is a documentation of techniques invented, results obtained and lessons learned while creating visualization algorithms to render outputs of large-scale seismic simulations. The objective is the development of techniques for a collaborative simulation and visualization shared between structural engineers, seismologists, and computer scientists. The computer graphics research community has been witnessing a large number of exemplary publications addressing the challenges faced while trying to visualize both large-scale surface and volumetric datasets lately. From a visualization perspective, issues like data preprocessing (simplification, sampling, filtering, etc.); rendering algorithms (surface and volume), and interaction paradigms (large-scale, highly interactive, highly immersive, etc.) have been areas of study. In this light, we outline and describe the milestones achieved in a large-scale simulation and visualization project, which opened the scope for combining existing techniques with new methods, especially in those cases where no existing methods were suitable. We elucidate the data simplification and reorganization schemes that we used, and discuss the problems we encountered and the solutions we found. We describe both desktop (high-end local as well as remote) interfaces and immersive visualization systems that we developed to employ interactive surface and volume rendering algorithms. Finally, we describe the results obtained, challenges that still need to be addressed, and ongoing efforts to meet the challenges of large-scale visualization.
Integration of measurement tools in medical 3d visualizations
Authors: Bernhard Preim, Christian Tietjen, Wolf Spindler, Heinz-Otto Peitgen
Published at Vis, 2002

We discuss 3d interaction techniques for the quantitative analysis of spatial relations in medical visualizations. We describe the design and implementation of measurement tools to measure distances, angles and volumes in 3d visualizations. The visualization of measurement tools as recognizable 3d objects and a 3d interaction, which is both intuitive and precise, determines the usability of such facilities. Measurements may be carried out in 2d visualizations of the original radiological data and in 3d visualizations. The result of a measurement carried out in one view is also displayed in the other view appropriately. We discuss the validation of the obtained measures. Finally, we describe how some important measurement tasks may be solved automatically.
Interactive rendering of large volume data sets
Authors: Stefan Guthe, Michael Wand 0001, Julius Gonser, Wolfgang Straßer
Published at Vis, 2002

We present a new algorithm for rendering very large volume data sets at interactive frame rates on standard PC hardware. The algorithm accepts scalar data sampled on a regular grid as input. The input data is converted into a compressed hierarchical wavelet representation in a preprocessing step. During rendering, the wavelet representation is decompressed on-the-fly and rendered using hardware texture mapping. The level of detail used for rendering is adapted to the local frequency spectrum of the data and its position relative to the viewer. Using a prototype implementation of the algorithm we were able to perform an interactive walkthrough of large data sets such as the visible human on a single off-the-shelf PC.
Interactive spectral volume rendering
Authors: Steven Bergner, Torsten Möller, Mark S. Drew, Graham D. Finlayson
Published at Vis, 2002

We describe a method for volume rendering using a spectral representation of colour instead of the traditional RGB model. It is shown how to use this framework for a novel exploration of datasets through enhanced transfer function design. Furthermore, our framework is extended to allow real-time re-lighting of the scene created with any rendering method. The technique of post-illumination is introduced to generate new spectral images for arbitrary light colours in real-time. Also a tool is described to design a palette of lights and materials having certain properties such as selective metamerism or colour constancy. Applied to spectral transfer functions, different light colours can accentuate or hide specific qualities of the data. In connection with post-illumination this provides a new degree of freedom for guided exploration of volumetric data, which cannot be achieved using the RGB model.
Interactive translucent volume rendering and procedural modeling
Authors: Joe Michael Kniss, Simon Premoze, Charles D. Hansen, David S. Ebert
Published at Vis, 2002

Direct volume rendering is a commonly used technique in visualization applications. Many of these applications require sophisticated shading models to capture subtle lighting effects and characteristics of volumetric data and materials. Many common objects and natural phenomena exhibit visual quality that cannot be captured using simple lighting models or cannot be solved at interactive rates using more sophisticated methods. We present a simple yet effective interactive shading model which captures volumetric light attenuation effects to produce volumetric shadows and the subtle appearance of translucency. We also present a technique for volume displacement or perturbation that allows realistic interactive modeling of high frequency detail for real and synthetic volumetric data.
Interactive view-dependent rendering of large isosurfaces
Authors: Benjamin F. Gregorski, Mark A. Duchaineau, Peter Lindstrom 0001, Valerio Pascucci, Kenneth I. Joy
Published at Vis, 2002

We present an algorithm for interactively extracting and rendering isosurfaces of large volume datasets in a view-dependent fashion. A recursive tetrahedral mesh refinement scheme, based on longest edge bisection, is used to hierarchically decompose the data into a multiresolution structure. This data structure allows fast extraction of arbitrary isosurfaces to within user specified view-dependent error bounds. A data layout scheme based on hierarchical space filling curves provides access to the data in a cache coherent manner that follows the data access pattern indicated by the mesh refinement.
Interactive visualization of complex plant ecosystems
Authors: Oliver Deussen, Carsten Colditz, Marc Stamminger, George Drettakis
Published at Vis, 2002

We present a method for interactive rendering of large outdoor scenes. Complex polygonal plant models and whole plant populations are represented by relatively small sets of point and line primitives. This enables us to show landscapes faithfully using only a limited percentage of primitives. In addition, a hierarchical data structure allows us to smoothly reduce the geometrical representation to any desired number of primitives. The scene is hierarchically divided into local portions of geometry to achieve large reduction factors for distant regions. Additionally, the data reduction is adapted to the visual importance of geometric objects. This allows us to maintain the visual fidelity of the representation while reducing most of the geometry drastically. With our system, we are able to interactively render very complex landscapes with good visual quality.
Isometric embedding by surface reconstruction from distances
Authors: Ingrid Hotz
Published at Vis, 2002

To display the intuitive meaning of an abstract metric it is helpful to look on an embedded surface with the same inner geometry as the given metric. The resulting partial differential equations have no standard solution. Only for some special cases satisfactory methods are known. I present a new algorithmic approach which is not based on differential equations. In contrast to other methods this technique also works if the embedding exists only locally. The fundamental idea is to estimate Euclidean distances, from which the surface is built up. In this paper I focus on the reconstruction of a surface from these estimated distances. Particular the influence of a perturbation of the distances on the shape of the resulting surface is investigated.
Kinetic visualization: a technique for illustrating 3D shape and structure
Authors: Eric B. Lum, Aleksander Stompel, Kwan-Liu Ma
Published at Vis, 2002

Motion provides strong visual cues for the perception of shape and depth, as demonstrated by cognitive scientists and visual artists. This paper presents a novel visualization technique-kinetic visualization -that uses particle systems to add supplemental motion cues which can aid in the perception of shape and spatial relationships of static objects. Based on a set of rules following perceptual and physical principles, particles flowing over the surface of an object not only bring out, but also attract attention to, essential information on the shape of the object that might not be readily visible with conventional rendering that uses lighting and view changes. Replacing still images with animations in this fashion, we demonstrate with both surface and volumetric models in the accompanying videos that in many cases the resulting visualizations effectively enhance the perception of three-dimensional shape and structure. The results of a preliminary user study that we have conducted also show evidence that the supplemental motion cues help.