DevLan/vispubs huggingface dataset:
Fast Algorithms for Visualizing Fluid Motion in Steady Flow on Unstructured Grids
Authors: Shyh-Kuang Ueng, Kris Sikorski, Kwan-Liu Ma
Published at Vis, 1995

The plotting of streamlines is an effective way of visualizing fluid motion in steady flows. Additional information about the flowfield, such as local rotation and expansion, can be shown by drawing in the form of a ribbon or tube. In this paper, we present efficient algorithms for the construction of streamlines, streamribbons and streamtubes on unstructured grids. A specialized version of the Runge-Kutta method has been developed to speed up the integration of particle pathes. We have also derived close-form solutions for calculating angular rotation rate and radius to construct streamribbons and streamtubes, respectively. According to our analysis and test results, these formulations are two to four times better in performance than previous numerical methods. As a large number of traces are calculated, the improved performance could be significant.
Fast multiresolution surface meshing
Authors: Markus H. Gross, Roger Gatti, Oliver G. Staadt
Published at Vis, 1995

Presents a new method for adaptive surface meshing and triangulation which controls the local level-of-detail of the surface approximation by local spectral estimates. These estimates are determined by a wavelet representation of the surface data. The basic idea is to decompose the initial data set by means of an orthogonal or semi-orthogonal tensor product wavelet transform (WT) and to analyze the resulting coefficients. In surface regions where the partial energy of the resulting coefficients is low, the polygonal approximation of the surface can be performed with larger triangles without losing too much fine-grain detail. However, since the localization of the WT is bound by the Heisenberg principle, the meshing method has to be controlled by the detail signals rather than directly by the coefficients. The dyadic scaling of the WT stimulated us to build a hierarchical meshing algorithm which transforms the initially regular data grid into a quadtree representation by rejection of unimportant mesh vertices. The optimum triangulation of the resulting quadtree cells is carried out by selection from a look-up table. The tree grows recursively, as controlled by the detail signals, which are computed from a modified inverse WT. In order to control the local level-of-detail, we introduce a new class of wavelet space filters acting as "magnifying glasses" on the data.
Fast normal estimation using surface characteristics
Authors: Byeong-Seok Shin, Yeong-Gil Shin
Published at Vis, 1995

To visualize the volume data acquired from computation or sampling, it is necessary to estimate normals at the points corresponding to object surfaces. Volume data does not holds the geometric information for the surface comprising points, so it is necessary to calculate normals using local information at each point. The existing normal estimation methods have some problems of estimating incorrect normals at discontinuous, aliased or noisy points. Yagel et al. (1992) solved some of these problems using their context-sensitive method. However, this method requires too much processing time and it loses some information on detailed parts of the object surfaces. This paper proposes the surface-characteristic-sensitive normal estimation method which applies different operators according to characteristics of each surface for the normal calculation. This method has the same advantages of the context-sensitive method, and also some other advantages such as less processing time and the reduction of the information loss on detailed parts.
Flow visualization in a hypersonic fin/ramp flow
Authors: Hans-Georg Pagendarm, Thomas Gerhold
Published at Vis, 1995

A recent study of a flow detail of an engine intake of future ground to orbit transport systems provided extremely complex data from numerical flow simulation and experimental flow visualization. The data posed a challenging problem to flow visualization, computational flow imaging (CFI), and the comparison of experimental imaging techniques versus computational imaging techniques. Some new visualization techniques have been implemented to provide compact representations of the complex features in the data. It turned out to be most useful to combine various specialized techniques for an icon-like representation of phenomena in a single image in order to study interaction of flow features. Some lessons were learned by simulating experimental visualization techniques on the numerical data.
High Dimensional Brushing for Interactive Exploration of Multivariate Data
Authors: Allen R. Martin, Matthew O. Ward
Published at Vis, 1995

Brushing is an operation found in many data visualization systems. It is a mechanism for interactively selecting subsets of the data so that they may be highlighted, deleted, or masked. Traditionally, brushes have been defined in screen space via methods such as painting and rubberband rectangles. In this paper we describe the design of N-dimensional brushes which are defined in data space rather than screen space, and show how they have been integrated into XmdvTool, a visualization package for displaying multivariate data. Depending on the data display technique in use, brushes may be specified and manipulated via direct or indirect methods, and the specification may be demand-driven or data-driven. Various brush operations such as highlighting, linking, masking, moving average, and quantitative display have been developed to apply to the selected data. In addition, we have explored several new brush concepts, such as non-discrete brush boundaries, simultaneous display of multiple brushes, and creating composite brushes via logical operators. Preliminary experimental evaluation with test subjects supports the usefulness of N-dimensional brushes in data exploration tasks.
High-speed volume rendering using redundant block compression
Authors: Günter Knittel
Published at Vis, 1995

Presents a novel volume rendering method which offers high rendering speed on standard workstations. It is based on a lossy data compression scheme which drastically reduces the memory bandwidth and computing requirements of perspective raycasting. Starting from classified and shaded data sets, we use block truncation coding or color cell compression to compress a block of 12 voxels into 32 bits. All blocks of the data set are processed redundantly, yielding a data structure which avoids multiple memory accesses per raypoint. As a side effect, the tri-linear interpolation of data coded in such a way is very much simplified. These techniques allow us to perform walkthroughs at interactive frame rates. Furthermore, the algorithm provides depth-cueing and the semi-transparent display of different materials. The algorithm achieves a sustained frame generation rate of about 2 Hz for large data sets (/spl sim/200/sup 3/) at an acceptable image quality on an SGI Indy workstation. A number of examples are shown.
Iconic techniques for feature visualization
Authors: Frank J. Post, Theo van Walsum, Frits H. Post, Deborah Silver
Published at Vis, 1995

Presents a conceptual framework and a process model for feature extraction and iconic visualization. Feature extraction is viewed as a process of data abstraction, which can proceed in multiple stages, and corresponding data abstraction levels. The features are represented by attribute sets, which play a key role in the visualization process. Icons are symbolic parametric objects, designed as visual representations of features. The attributes are mapped to the parameters (or degrees of freedom) of an icon. We describe some generic techniques to generate attribute sets, such as volume integrals and medial axis transforms. A simple but powerful modeling language was developed to create icons, and to link the attributes to the icon parameters. We present illustrative examples of iconic visualization created with the techniques described, showing the effectiveness of this approach.
IFS fractal interpolation for 2D and 3D visualization
Authors: Craig M. Wittenbrink
Published at Vis, 1995

Reconstruction is used frequently in visualization of one, two, and three dimensional data. Data uncertainty is typically ignored, and a deficiency of many interpolation schemes is smoothing which may indicate features or characteristics of the data that are not there. The author investigates the use of iterated function systems (IFS's) for interpolation. He shows new derivations for fractal interpolation in two and three dimensional scalar data, and new point and polytope rendering algorithms with tremendous speed advantages over ray tracing. The interpolations may be used to give an indication of the uncertainty of the data, statistically represent the data at a variety of scales, allow tunability from the data, and may allow more accurate data analysis.
Interactive 3D visualization of actual anatomy and simulated chemical time-course data for fish
Authors: Penny Rheingans, Martin Marietta, John Nichols
Published at Vis, 1995

Outputs from a physiologically based toxicokinetic (PB-TK) model for fish were visualized by mapping time series data for specific tissues onto a three dimensional representation of a rainbow trout. The trout representation was generated in stepwise fashion: cross sectional images were obtained from an anesthetized fish using a magnetic resonance imaging (MRI) system; images were processed to classify tissue types; images were stacked and processed to create a three dimensional representation of the fish, encapsulating five volumes corresponding to the liver, kidney, muscle, gastrointestinal tract, and fat. Kinetic data for the disposition of pentachloroethane in trout were generated using a PB-TK model. Model outputs were mapped onto corresponding tissue volumes, representing chemical concentration as color intensity. The visualization was then animated, to show the accumulation of pentachloroethane in each tissue during a continuous branchial (gill) exposure.
Interactive maximum projection volume rendering
Authors: Michael D. McCool, Wolfgang Heidrich, John Stevens
Published at Vis, 1995

Maximum projection is a volume rendering technique that, for each pixel, finds the maximum intensity along a projector. For certain important classes of data, this is an approximation to summation rendering which produces superior visualizations. We show how maximum projection rendering with additional depth cues can be implemented using simple affine transformations in object space. This technique can be used together with 3D graphics libraries and standard graphics hardware, thus allowing interactive manipulations of the volume data. The algorithm presented allows for a wide range of tradeoffs between interactivity and image quality.
Interactive realism for visualization using ray tracing
Authors: Robert A. Cross
Published at Vis, 1995

Visual realism is necessary for many virtual reality applications. In order to convince the user that the virtual environment is real, the scene presented should faithfully model the expected actual environment. A highly accurate, fully modeled, interactive environment is thus seen as "virtually real". The paper addresses the problem of interactive visual realism and discusses a possible solution: a hybrid rendering paradigm that ties distributed graphics hardware and ray tracing systems together for use in interactive, high visual realism applications. This new paradigm is examined in the context of a working rendering system. This system is capable of producing images of higher fidelity than possible through the use of graphics hardware alone, able both to render images at speeds useful for interactive systems and to progressively refine static, high quality snapshots.
Interactive visualization of mixed scalar and vector fields
Authors: Lichan Hong, Xiaoyang Mao, Arie E. Kaufman
Published at Vis, 1995

This paper describes an approach for interactive visualization of mixed scalar and vector fields, in which vector icons are generated from pre-voxelized icon templates and volume-rendered together with the volumetric scalar data. This approach displays simultaneously the global structure of the scalar field and the detailed features of the vector field. Interactive visualization is achieved with incremental image update, by re-rendering only a small portion of the image wherever and whenever a change occurs. This technique supports a set of interactive visualization tools, including change of vector field visualization parameters, real-time animation of vector icons advected within the scalar field, a zooming lens, and a local probe.
Interval set: a volume rendering technique generalizing isosurface extraction
Authors: Baining Guo
Published at Vis, 1995

A scalar volume V={(x,f(x))|x/spl isin/R} is described by a function f(x) defined over some region R of the three dimensional space. The paper presents a simple technique for rendering interval sets of the form I/sub g/(a,b)={(x,f(x))|a/spl les/g(x)/spl les/b}, where a and b are either real numbers of infinities. We describe an algorithm for triangulating interval sets as /spl alpha/ shapes, which can be accurately and efficiently rendered as surfaces or semi transparent clouds. On the theoretical side, interval sets provide an unified approach to isosurface extraction and direct volume rendering. On the practical side, interval sets add flexibility to scalar volume visualization-we may choose to, for example, have an interactive, high quality display of the volume surrounding or "inside" an isosurface when such display for the entire volume is too expensive to produce.
Interval volume: a solid fitting technique for volumetric data display and analysis
Authors: Issei Fujishiro, Yuji Maeda, Hiroshi Sato
Published at Vis, 1995

Proposes as a generalization of isosurfaces, the 'interval volume', which is a new type of geometric model representing 3D subvolumes with field values belonging to a closed interval. A dominant surface fitting algorithm called 'marching cubes' is extended to obtain a solid fitting algorithm, which extracts from a given volumetric dataset a high-resolution polyhedral solid data structure of the interval volume. Rendering methods for the interval volume and principal related operations are also presented. The effectiveness of this approach is illustrated with 4D simulated data from atomic collision research.
Legibility enhancement for information visualisation
Authors: Rob Ingram, Steve Benford
Published at Vis, 1995

Navigation in computer generated information spaces may be difficult, resulting in users getting "lost in hyperspace". This work aims to build on research from the area of city planning to try to solve this problem. We introduce the concepts of legibility and cognitive maps and the five features of urban landscape with which they are associated. Following this will be descriptions of techniques and algorithms which we have developed to allow these features to be introduced to three dimensional spaces for information visualisation. Next we describe a specific application of these techniques in the visualisation of the World Wide Web and conclude with a look at future development of the system.
Marching through the Visible Man
Authors: William E. Lorensen
Published at Vis, 1995

The National Library of Medicine is creating a digital atlas of the human body. This project, called the Visible Human, has already produced computed tomography, magnetic resonance imaging and physical cross-sections of a human male cadaver. This paper describes a methodology and results for extracting surfaces from the Visible Male's CT data. We use surface connectivity and isosurface extraction techniques to create polygonal models of the skin, bone, muscle and bowels. We also report early experiments with the physical cross-sections.
On enhancing the speed of splatting with indexing
Authors: Insung Ihm, Rae Kyoung Lee
Published at Vis, 1995

Splatting is an object space direct volume rendering algorithm that produces images of high quality, but is computationally expensive like many other volume rendering algorithms. The paper presents a new technique that enhances the speed of splatting without trading off image quality. This new method reduces rendering time by employing a simple indexing mechanism which allows to visit and splat only the voxels of interest. It is shown that this algorithm is suitable for the dynamic situation in which viewing parameters and opacity transfer functions change interactively. We report experimental results on several test data sets of useful site and complexity, and discuss the cost/benefit trade off of our method.
Optimization of time-dependent particle tracing using tetrahedral decomposition
Authors: David N. Kenwright, David A. Lane
Published at Vis, 1995

An efficient algorithm is presented for computing particle paths, streak lines and time lines in time-dependent flows with moving curvilinear grids. The integration, velocity interpolation, and step size control are all performed in physical space which avoids the need to transform the velocity field into computational space. This leads to higher accuracy because there are no Jacobian matrix approximations, and expensive matrix inversions are eliminated. Integration accuracy is maintained using an adaptive step size control scheme which is regulated by the path line curvature. The problem of point location and interpolation in physical space is simplified by decomposing hexahedral cells into tetrahedral cells. This enables the point location to be done analytically and substantially faster than with a Newton-Raphson iterative method. Results presented show this algorithm is up to six times faster than particle tracers which operate on hexahedral cells, and produces almost identical traces.
Pictorial statistics-visualization of high-dimensional statistical distributions
Authors: Andreas A. Müller
Published at Vis, 1995

A general framework for visualization of statistical properties of high-dimensional pattern samples and the related computational steps are introduced. These procedures are exemplified on applications in anthropometrical research (shape information in faces) but can be easily generalized to various other morphometrical questions and data sets with pattern structure, e.g., data stemming from sensor arrays. Presently, the visualization techniques illustrated concentrate on (higher) moments of first order. It is suggested, how moments of second order can be visualized by animations and how this approach can be used in the context of comparative visualization.
Propositional n-traces: visualizing a problem in philosophical logic
Authors: Nathalie Prevost, Ray E. Jennings, Loki Jörgenson, F. David Fracchia
Published at Vis, 1995

As part of an inter-disciplinary effort, we are visually exploring a current problem in philosophical logic related to information processing. Given a set of inconsistent sentences or inputs, a processor cannot unambiguously infer any specific consequence. Traces represent subsets of possible consequences which can be inferred classically from partitions of the set of inputs. We are interested in the relationship between a given set of Boolean inputs and its respective trace(s). We have developed a visualization paradigm which allows us to view and explore this relationship effectively.
Qualitative analysis of invariant tori in a dynamical system
Authors: Daryl H. Hepting, Gianne Derks, Kossi D. Edoh, Robert D. Russell
Published at Vis, 1995

Invariant tori are examples of invariant manifolds in dynamical systems. Usual tools in dynamical systems such as analysis and numerical simulations alone are often not sufficient to understand the complicated mechanisms that cause changes in these manifolds. Computer-graphical visualization is a natural and powerful addition to these tools used for the qualitative study of dynamical systems, especially for the study of invariant manifolds. The dynamics of two linearly coupled oscillators is the focus of this case study. With little or no coupling between the oscillators, an invariant torus is present but it breaks down for strong coupling. Visualization has been employed to gain a qualitative understanding of this breakdown process. The visualization has allowed key features of the tori to be recognized, and it has proven to be indispensable in developing and testing hypotheses about the tori.
Recursive pattern: a technique for visualizing very large amounts of data
Authors: Daniel A. Keim, Mihael Ankerst, Hans-Peter Kriegel
Published at Vis, 1995

An important goal of visualization technology is to support the exploration and analysis of very large amounts of data. In this paper, we propose a new visualization technique called a 'recursive pattern', which has been developed for visualizing large amounts of multidimensional data. The technique is based on a generic recursive scheme which generalizes a wide range of pixel-oriented arrangements for displaying large data sets. By instantiating the technique with adequate data- and application-dependent parameters, the user may greatly influence the structure of the resulting visualizations. Since the technique uses one pixel for presenting each data value, the amount of data which can be displayed is only limited by the resolution of current display technology and by the limitations of human perceptibility. Beside describing the basic idea of the 'recursive pattern' technique, we provide several examples of useful parameter settings for the various recursion levels. We further show that our 'recursive pattern' technique is particularly advantageous for the large class of data sets which have a natural order according to one dimension (e.g. time series data). We demonstrate the usefulness of our technique by using a stock market application.
Space walking
Authors: Andrew J. Hanson, Hui Ma
Published at Vis, 1995

Proposes an interactive method for exploring topological spaces based on the natural local geometry of the space. Examples of spaces appropriate for this visualization approach occur in abundance in mathematical visualization, surface and volume visualization problems, and scientific applications such as general relativity. Our approach is based on using a controller to choose a direction in which to "walk" a manifold along a local geodesic path. The method automatically generates orientation changes that produce a maximal viewable region with each step of the walk. The proposed interaction framework has many natural properties to help the user develop a useful cognitive map of a space and is well-suited to haptic interfaces that may be incorporated into desktop virtual reality systems.
Splatting of curvilinear volumes
Authors: Xiaoyang Mao, Lichan Hong, Arie E. Kaufman
Published at Vis, 1995

The paper presents a splatting algorithm for volume rendering of curvilinear grids. A stochastic sampling technique called Poisson sphere/ellipsoid sampling is employed to adaptively resample a curvilinear grid with a set of randomly distributed points whose energy support extents are well approximated by spheres and ellipsoids. Filter kernels corresponding to these spheres and ellipsoids are used to generate the volume rendered image of the curvilinear grid with a conventional footprint evaluation algorithm. Experimental results show that our approach can be regarded as an alternative to existing fast volume rendering techniques of curvilinear grids.