DevLan/vispubs huggingface dataset:
Detecting null alleles with vasarely charts
Authors: Carl Manaster, Elizabeth Nanthakumar, Phillip A. Morin
Published at Vis, 1999

Microsatellite genotypes can have problems that are difficult to detect with existing tools. One such problem is null alleles. This paper presents a new visualization tool that helps to find and characterize these errors. The paper explains how the tool is used to analyze groups of genotypes and proposes other possible uses.
Detecting vortical phenomena in vector data by medium-scale correlation
Authors: Hans-Georg Pagendarm, Birgit Henne, Markus Rütten
Published at Vis, 1999

The detection of vortical phenomena in vector data is one of the key issues in many technical applications, in particular in flow visualization. Many existing approaches rely on purely local evaluation of the vector data. In order to overcome the limits of a local approach, we choose to combine a local method with a correlation of a pre-defined generic vortex with the data in a medium-scale region. Two different concepts of generic vortices were tested on various sets of flow velocity vector data. The approach is not limited to the two generic patterns suggested here. The method was found to successfully detect vortices in cases were other methods fail.
Digital design of a surgical simulator for interventional MR imaging
Authors: Terry S. Yoo, Penny Rheingans
Published at Vis, 1999

We present the design of a simulator for a prototype interventional magnetic resonance imaging scanner. This MRI scanner is integrated with an operating theater, enabling new techniques in minimally invasive surgery. The simulator is designed with a threefold purpose: to provide a rehearsal apparatus for practicing and modifying conventional procedures for use in the magnetic environment; to serve as a visualization workstation for procedure planning and previewing as well as a post-operative review; and to form the foundation of a laboratory workbench for the development of new surgical tools and procedures for minimally invasive surgery. The simulator incorporates pre-operative data, either MRI or CT exams, as well as data from commercial surgical planning systems. Dynamic control of the simulation and interactive display of pre-operative data in lieu of intra-operative data is handled via an opto-electronic tracking system. The resulting system is contributing insights into how best to perform visualization for this new surgical environment.
Efficient compression of non-manifold polygonal meshes
Authors: André Guéziec, Frank Bossen, Gabriel Taubin, Cláudio T. Silva
Published at Vis, 1999

We present a method for compressing non-manifold polygonal meshes, i.e. polygonal meshes with singularities, which occur very frequently in the real-world. Most efficient polygonal compression methods currently available are restricted to a manifold mesh: they require a conversion process, and fail to retrieve the original model connectivity after decompression. The present method works by converting the original model to a manifold model, encoding the manifold model using an existing mesh compression technique, and clustering, or stitching together during the decompression process vertices that were duplicated earlier to faithfully recover the original connectivity. This paper focuses on efficiently encoding and decoding the stitching information. By separating connectivity from geometry and properties, the method avoids encoding vertices (and properties bound to vertices) multiple times; thus a reduction of the size of the bit-stream of about 10% is obtained compared with encoding the model as a manifold.
Enabling Classification and Shading for 3D Texture Mapping based Volume Rendering using OpenGL and Extensions
Authors: Michael Meißner, Ulrich Hoffmann, Wolfgang Straßer
Published at Vis, 1999

We present a new technique which enables direct volume rendering based on 3D texture mapping hardware, enabling shading as well as classification of the interpolated data. Our technique supports accurate lighting for a one directional light source, semi-transparent classification, and correct blending. To circumvent the limitations of one general classification, we introduce multiple classification spaces which are very valuable to understand the visualized data, and even mandatory to comprehensively grasp the 3D relationship of different materials present in the volumetric data. Furthermore, we illustrate how multiple classification spaces can be realized using existing graphics hardware. In contrast to previously reported algorithms, our technique is capable of performing all the above mentioned tasks within the graphics pipeline. Therefore, it is very efficient: The three dimensional texture needs to be stored only once and no load is put onto the CPU. Besides using standard OpenGL functionality, we exploit advanced per pixel operations and make use of available OpenGL extensions.
Exploring geo-scientific data in virtual environments
Authors: Bernd Fröhlich 0001, Stephen Barrass, Björn Zehner, John Plate, Martin Göbel
Published at Vis, 1999

This paper describes tools and techniques for the exploration of gee-scientific data from the oil and gas domain in stereoscopic virtual environments. The two main sources of data in the exploration task are seismic volumes and multivariate well logs of physical properties down a bore hole. We have developed a props-based interaction device called the cubic mouse to allow more direct and intuitive interaction with a cubic seismic volume. This device effectively places the seismic cube in the user's hand. Geologists who have tried this device have been enthusiastic about the ease of use, and were adept only a few moments after picking it up. We have also developed a multi-modal, visualisation and sonification technique for the dense, multivariate well log data. The visualisation can show two well log variables mapped along the well geometry in a bivariate colour scheme, and another variable on a sliding lens. A sonification probe is attached to the lens so that other variables can be heard. The sonification is based on a Geiger-counter metaphor that is widely understood and which makes it easy to explain. The data is sonified at higher or lower resolutions depending on the speed of the lens. Sweeps can be made at slower rates and over smaller intervals to home in on peaks, boundaries or other features in the full resolution data set.
Feature Comparisons Of 3-D Vector Fields Using Earth Mover's Distance
Authors: Rajesh Batra, Lambertus Hesselink
Published at Vis, 1999

A method for comparing three-dimensional vector fields constructed from simple critical points is described. This method is a natural extension of previous work (Y. Lavin et al., 1998), which defined a distance metric for comparing two-dimensional fields. The extension to three-dimensions follows the path of our previous work, rethinking the representation of a critical point signature and the distance measure between the points. Since the method relies on topologically based information, problems such as grid matching and vector alignment which often complicate other comparison techniques are avoided. In addition, since only feature information is used to represent, and is therefore stored for each field, a significant amount of compression occurs.
Forward image mapping
Authors: Baoquan Chen, Frank Dachille, Arie E. Kaufman
Published at Vis, 1999

We present a novel forward image mapping algorithm, which speeds up perspective warping, as in texture mapping. It processes the source image in a special scanline order instead of the normal raster scanline order. This special scanline has the property of preserving parallelism when projecting to the target image. The algorithm reduces the complexity of perspective-correct image warping by eliminating the division per pixel and replacing it with a division per scanline. The method also corrects the perspective distortion in Gouraud shading with negligible overhead. Furthermore, the special scanline order is suitable for antialiasing using a more accurate antialiasing conic filter, with minimum additional cost. The algorithm is highlighted by incremental calculations and optimized memory bandwidth by reading each source pixel only once, suggesting a potential hardware implementation.
Geo-spatial visualization for situational awareness
Authors: Eliot Feibush, Nikhil Gagvani, Daniel Williams
Published at Vis, 1999

Situational awareness applications require a highly detailed geospatial visualization covering a large geographic area. Conventional polygon based terrain modeling would exceed the capacity of current computer rendering. Terrain visualization techniques for a situational awareness application are described in this case study. Visualizing large amounts of terrain data has been achieved using very large texture maps. Sun shading is applied to the terrain texture map to enhance perception of relief features. Perception of submarine positions has been enhanced using a translucent, textured water surface.
Hierarchical parallel coordinates for exploration of large datasets
Authors: Ying-Huey Fua, Matthew O. Ward, Elke A. Rundensteiner
Published at Vis, 1999

Our ability to accumulate large, complex (multivariate) data sets has far exceeded our ability to effectively process them in searching for patterns, anomalies and other interesting features. Conventional multivariate visualization techniques generally do not scale well with respect to the size of the data set. The focus of this paper is on the interactive visualization of large multivariate data sets based on a number of novel extensions to the parallel coordinates display technique. We develop a multi-resolution view of the data via hierarchical clustering, and use a variation of parallel coordinates to convey aggregation information for the resulting clusters. Users can then navigate the resulting structure until the desired focus region and level of detail is reached, using our suite of navigational and filtering tools. We describe the design and implementation of our hierarchical parallel coordinates system which is based on extending the XmdvTool system. Lastly, we show examples of the tools and techniques applied to large (hundreds of thousands of records) multivariate data sets.
High performance presence-accelerated ray casting
Authors: Ming Wan, Arie E. Kaufman, Steve Bryson
Published at Vis, 1999

We present a novel presence acceleration for volumetric ray casting. A highly accurate estimation for object presence is obtained by projecting all grid cells associated with the object boundary on the image plane. Memory space and access time are reduced by run-length encoding of the boundary cells, while boundary cell projection time is reduced by exploiting projection templates and multiresolution volumes. Efforts have also been made towards a fast perspective projection as well as interactive classification. We further present task partitioning schemes for effective parallelization of both boundary cell projection and ray traversal procedures. Good load balancing has been reached by taking full advantage of both the optimizations in the serial rendering algorithm and shared-memory architecture. Our experimental results on a 16-processor SGI Power Challenge have shown interactive rendering rates for 256/sup 3/ volumetric data sets at 10-30 Hz. We describe the theory and implementation of our algorithm, and shows its superiority over the shear-warp factorization approach.
Hue-balls and lit-tensors for direct volume rendering of diffusion tensor fields
Authors: Gordon L. Kindlmann, David M. Weinstein
Published at Vis, 1999

With the development of magnetic resonance imaging techniques for acquiring diffusion tensor data from biological tissue, visualization of tensor data has become a new research focus. The diffusion tensor describes the directional dependence of water molecules' diffusion and can be represented by a three-by-three symmetric matrix. Visualization of second-order tensor fields is difficult because the data values have many degrees of freedom. Existing visualization techniques are best at portraying the tensor's properties over a two-dimensional field, or over a small subset of locations within a three-dimensional field. A means of visualizing the global structure in measured diffusion tensor data is needed. We propose the use of direct volume rendering, with novel approaches for the tensors' coloring, lighting, and opacity assignment. Hue-balls use a two-dimensional colormap on the unit sphere to illustrate the tensor's action as a linear operator. Lit-tensors provide a lighting model for tensors which includes as special cases both lit-lines (from streamline vector visualization) and standard Phong surface lighting. Together with an opacity assignment based on a novel two-dimensional barycentric space of anisotropy, these methods are shown to produce informative renderings of measured diffusion tensor data from the human brain.
Image graphs-a novel approach to visual data exploration
Authors: Kwan-Liu Ma
Published at Vis, 1999

For types of data visualization where the cost of producing images is high, and the relationship between the rendering parameters and the image produced is less than obvious, a visual representation of the exploration process can make the process more efficient and effective. Image graphs represent not only the results but also the process of data visualization. Each node in an image graph consists of an image and the corresponding visualization parameters used to produce it. Each edge in a graph shows the change in rendering parameters between the two nodes it connects. Image graphs are not just static representations; users can interact with a graph to review a previous visualization session or to perform new rendering. Operations which cause changes in rendering parameters can propagate through the graph. The user can take advantage of the information in image graphs to understand how certain parameter changes affect visualization results. Users can also share image graphs to streamline the process of collaborative visualization. We have implemented a volume visualization system using the image graph interface, and the examples presented come from this application.
Implant sprays: compression of progressive tetrahedral mesh connectivity
Authors: Renato Pajarola, Jarek Rossignac, Andrzej Szymczak
Published at Vis, 1999

Irregular tetrahedral meshes, which are popular in many engineering and scientific applications, often contain a large number of vertices. A mesh of V vertices and T tetrahedra requires 48 V bits or less to store the vertex coordinates, 4/spl middot/T/spl middot/log/sub 2/(V) bits to store the tetrahedra-vertex incidence relations, also called connectivity information, and kV bits to store the k-bit value samples associated with the vertices. Given that T is 5 to 7 times larger than V and that V often exceeds 32/sup 3/, the storage space required for the connectivity is larger than 300 V bits and thus dominates the overall storage cost. Our "implants spray" compression approach introduced in the paper reduces this cost to about 30 V bits or less-a 10:1 compression ratio. Furthermore, implant spray supports the progressive refinement of a crude model through a series of vertex-splits operations.
Interactive exploration of extra- and interacranial blood vessels
Authors: Dirk Bartz, Wolfgang Straßer, Martin Skalej, Dorothea Welte
Published at Vis, 1999

We present a system for interactive explorations of extra- and intracranial blood vessels. Starting with a stack of images from 3D angiography, we use virtual clips to limit the segmentation of the vessel tree to the parts the neuroradiologists are interested in. Furthermore, methods of interactive virtual endoscopy are applied in order to provide an interior view of the blood vessels.
Interactive exploration of volume line integral convolution based on 3D-texture mapping
Authors: Christof Rezk-Salama, Peter Hastreiter, Christian Teitzel, Thomas Ertl
Published at Vis, 1999

Line integral convolution (LIC) is an effective technique for visualizing vector fields. The application of LIC to 3D flow fields has yet been limited by difficulties to efficiently display and animate the resulting 3D-images. Texture-based volume rendering allows interactive visualization and manipulation of 3D-LIC textures. In order to ensure the comprehensive and convenient exploration of flow fields, we suggest interactive functionality including transfer functions and different clipping mechanisms. Thereby, we efficiently substitute the calculation of LIC based on sparse noise textures and show the convenient visual access of interior structures. Further on, we introduce two approaches for animating static 3D-flow fields without the computational expense and the immense memory requirements for pre-computed 3D-textures and without loss of interactivity. This is achieved by using a single 3D-LIC texture and a set of time surfaces as clipping geometries. In our first approach we use the clipping geometry to pre-compute a special 3D-LIC texture that can be animated by time-dependent color tables. Our second approach uses time volumes to actually clip the 3D-LIC volume interactively during rasterization. Additionally, several examples demonstrate the value of our strategy in practice.
Interactive lens visualization techniques
Authors: Chris Shaw 0002, James A. Hall, David S. Ebert, D. Aaron Roberts
Published at Vis, 1999

The paper describes new techniques for minimally immersive visualization of 3D scalar and vector fields, and visualization of document corpora. In our glyph based visualization system, the user interacts with the 3D volume of glyphs using a pair of button-enhanced 3D position and orientation trackers. The user may also examine the volume using an interactive lens, which is a rectangle that slices through the 3D volume and displays scalar information on its surface. A lens allows the display of scalar data in the 3D volume using a contour diagram, and a texture based volume rendering.
Interactive visualization of fluid dynamics simulations in locally refined cartesian grids
Authors: Martin Schulz 0005, Frank Reck, Wolf Bartelheimer, Thomas Ertl
Published at Vis, 1999

The work presents interactive flow visualization techniques specifically adapted for PowerFLOW/sup TM/, a lattice based CFD code from the EXA corporation. Their Digital Physics/sup TM/ fluid simulation technique is performed on a hierarchy of locally refined cartesian grids with a fine voxel resolution in areas of interesting flow features. Among other applications, the PowerFLOW solver is used for aerodynamic simulations in car body development where the advantages of automatic grid generation from CAD models is of great interest. In a joint project with BMW and EXA, we are developing a visualization tool which incorporates virtual reality techniques for the interactive exploration of the large scalar and vector data sets. We describe the specific data structures and interpolation techniques and we report on fast particle tracing, taking into account collisions with the car body geometry. An OpenGL Optimizer based implementation allows for the inspection of the flow with particle probes and slice probes at interactive frame rates.
Isosurface extraction in time-varying fields using a Temporal Branch-on-Need Tree (T-BON)
Authors: Philip M. Sutton, Charles D. Hansen
Published at Vis, 1999

The Temporal Branch-on-Need Tree (T-BON) extends the three dimensional branch-on-need octree for time-varying isosurface extraction. At each time step, only those portions of the tree and data necessary to construct the current isosurface are read from disk. This algorithm can thus exploit the temporal locality of the isosurface and, as a geometric technique, spatial locality between cells in order to improve performance. Experimental results demonstrate the performance gained and memory overhead saved using this technique.
Isosurface extraction techniques for Web-based volume visualization
Authors: Klaus Engel, Rüdiger Westermann, Thomas Ertl
Published at Vis, 1999

The reconstruction of isosurfaces from scalar volume data has positioned itself as a fundamental visualization technique in many different applications. But the dramatically increasing size of volumetric data sets often prohibits the handling of these models on affordable low-end single processor architectures. Distributed client-server systems integrating high-bandwidth transmission channels and Web based visualization tools are one alternative to attack this particular problem, but therefore new approaches to reduce the load of numerical processing and the number of generated primitives are required. We outline different scenarios for distributed isosurface reconstruction from large scale volumetric data sets. We demonstrate how to directly generate stripped surface representations and we introduce adaptive and hierarchical concepts to minimize the number of vertices that have to be reconstructed, transmitted and rendered. Furthermore, we propose a novel computation scheme, which allows the user to flexibly exploit locally available resources. The proposed algorithms have been merged together in order to build a platform-independent Web based application. Extensive use of VRML and Java OpenGL bindings allows for the exploration of large scale volume data quite efficiently.
Large field visualization with demand-driven calculation
Authors: Patrick J. Moran, Chris Henze
Published at Vis, 1999

Presents a system designed for the interactive definition and visualization of fields derived from large data sets: the Demand-Driven Visualizer (DDV). The system allows the user to write arbitrary expressions to define new fields, and then apply a variety of visualization techniques to the result. Expressions can include differential operators and numerous other built-in functions. Determination of field values, both in space and in time, is directed automatically by the demands of the visualization techniques. The payoff of following a demand-driven design philosophy throughout the visualization system becomes particularly evident when working with large time-series data, where the costs of eager evaluation alternatives can be prohibitive.
LOD-sprite technique for accelerated terrain rendering
Authors: Baoquan Chen, J. Edward Swan II, Eddy Kuo, Arie E. Kaufman
Published at Vis, 1999

We present a novel rendering technique, termed LOD-sprite rendering, which uses a combination of a level-of-detail (LOD) representation of the scene together with reusing image sprites (previously rendered images). Our primary application is accelerating terrain rendering. The LOD-sprite technique renders an initial frame using a high-resolution model of the scene geometry. It renders subsequent frames with a much lower-resolution model of the scene geometry and texture-maps each polygon with the image sprite from the initial high-resolution frame. As it renders these subsequent frames, the technique measures the error associated with the divergence of the view position from the position where the initial frame was rendered. Once this error exceeds a user-defined threshold, the technique re-renders the scene from the high-resolution model. We have efficiently implemented the LOD-sprite technique with texture mapping graphics hardware. Although to date we have only applied LOD-sprite to terrain rendering, it could easily be extended to other applications. We feel LOD-sprite holds particular promise for real time rendering systems.
Mixing translucent polygons with volumes
Authors: Kevin Kreeger, Arie E. Kaufman
Published at Vis, 1999

We present an algorithm which renders opaque and/or translucent polygons embedded within volumetric data. The processing occurs such that all objects are composited in the correct order, by rendering thin slabs of the translucent polygons between volume slices using slice-order volume rendering. We implemented our algorithm with OpenGL on current general-purpose graphics systems. We discuss our system implementation, speed and image quality, as well as the renderings of several mixed scenes.