DevLan/vispubs huggingface dataset:
Multi-projector displays using camera-based registration
Authors: Ramesh Raskar, Michael S. Brown, Ruigang Yang, Wei-Chao Chen, Greg Welch, Herman Towles, W. Brent Seales, Henry Fuchs
Published at Vis, 1999

Conventional projector-based display systems are typically designed around precise and regular configurations of projectors and display surfaces. While this results in rendering simplicity and speed, it also means painstaking construction and ongoing maintenance. In previously published work, we introduced a vision of projector-based displays constructed from a collection of casually-arranged projectors and display surfaces. In this paper, we present flexible yet practical methods for realizing this vision, enabling low-cost mega-pixel display systems with large physical dimensions, higher resolution, or both. The techniques afford new opportunities to build personal 3D visualization systems in offices, conference rooms, theaters, or even your living room. As a demonstration of the simplicity and effectiveness of the methods that we continue to perfect, we show in the included video that a 10-year old child can construct and calibrate a two-camera, two-projector, head-tracked display system, all in about 15 minutes.
Multi-resolution multi-field ray tracing: a mathematical overview
Authors: Charidimos E. Gasparakis
Published at Vis, 1999

A rigorous mathematical review of ray tracing is presented. The concept of a generic voxel decoder acting on flexible voxel formats is introduced. The necessity of interpolating opacity weighted colors is proved, using a new definition of the blending process in terms of functional integrals. The continuum limit of the discrete opacity accumulation formula is presented, and its convexity properties are investigated. The issues pertaining to interpolation/classification order are discussed. The lighting equation is expressed in terms of opacity weighted colors. The multi-resolution (along the ray) correction of the opacity-weighted color is derived. The mathematics of filtering on the image plane are studied, and an upper limit of the local pixel size on the image plane is obtained. Interpolation of pixel values on the image plane is shown to be in-equivalent to blending of interpolated samples.
Multiresolution Techniques for Interactive Texture-based Volume Visualization
Authors: Eric LaMar, Bernd Hamann, Kenneth I. Joy
Published at Vis, 1999

We present a multiresolution technique for interactive texture-based volume visualization of very large data sets. This method uses an adaptive scheme that renders the volume in a region-of-interest at a high resolution and the volume away from this region at progressively lower resolutions. The algorithm is based on the segmentation of texture space into an octree, where the leaves of the tree define the original data and the internal nodes define lower-resolution versions. Rendering is done adaptively by selecting high-resolution cells close to a center of attention and low-resolution cells away from this area. We limit the artifacts introduced by this method by modifying the transfer functions in the lower-resolution data sets and utilizing spherical shells as a proxy geometry. It is possible to use this technique to produce viewpoint-dependent renderings of very large data sets.
New quadric metric for simplifying meshes with appearance attributes
Authors: Hugues Hoppe
Published at Vis, 1999

Complex triangle meshes arise naturally in many areas of computer graphics and visualization. Previous work has shown that a quadric error metric allows fast and accurate geometric simplification of meshes. This quadric approach was recently generalized to handle meshes with appearance attributes. In this paper we present an improved quadric error metric for simplifying meshes with attributes. The new metric, based on geometric correspondence in 3D, requires less storage, evaluates more quickly, and results in more accurate simplified meshes. Meshes often have attribute discontinuities, such as surface creases and material boundaries, which require multiple attribute vectors per vertex. We show that a wedge-based mesh data structure captures such discontinuities efficiently and permits simultaneous optimization of these multiple attribute vectors. In addition to the new quadric metric, we experiment with two techniques proposed in geometric simplification, memoryless simplification and volume preservation, and show that both of these are beneficial within the quadric framework. The new scheme is demonstrated on a variety of meshes with colors and normals.
Optimal triangular Haar bases for spherical data
Authors: Georges-Pierre Bonneau
Published at Vis, 1999

Multiresolution analysis based on FWT (Fast Wavelet Transform) is now widely used in scientific visualization. Spherical biorthogonal wavelets for spherical triangular grids were introduced by P. Schroder and W. Sweldens (1995). In order to improve on the orthogonality of the wavelets, the concept of nearly orthogonality, and two new piecewise-constant (Haar) bases were introduced by G.M. Nielson (1997). We extend the results of Nielson. First we give two one-parameter families of triangular Haar wavelet bases that are nearly orthogonal in the sense of Nielson. Then we introduce a measure of orthogonality. This measure vanishes for orthogonal bases. Eventually, we show that we can find an optimal parameter of our wavelet families, for which the measure of orthogonality is minimized. Several numerical and visual examples for a spherical topographic data set illustrates our results.
PLIC: bridging the gap between streamlines and LIC
Authors: Vivek Verma, David L. Kao, Alex T. Pang
Published at Vis, 1999

This paper explores mapping strategies for generating LIC-like images from streamlines and streamline-like images from LIC. The main contribution of this paper is a technique which we call pseudo-LIC or PLIC. By adjusting a small set of key parameters, PLIC can generate flow visualizations that span the spectrum of streamline-like to LIC-like images. Among the advantages of PLIC are: image quality comparable with LIC, performance speedup over LIC, use of a template texture that is independent of the size of the flow field, handles the problem of multiple streamlines occupying the same pixel in image space, reduced aliasing, applicability to time varying data sets, and variable speed animation.
Progressive compression and transmission of arbitrary triangular meshes
Authors: Chandrajit L. Bajaj, Valerio Pascucci, Guozhong Zhuang
Published at Vis, 1999

The recent growth in the size and availability of large triangular surface models has generated interest in compact multi-resolution progressive representation and data transmission. An ongoing challenge is to design an efficient data structure that encompasses both compactness of geometric representations and visual quality of progressive representations. We introduce a topological layering based data structure and an encoding scheme to build a compact progressive representation of an arbitrary triangular mesh (a 2D simplicial complex in 3D) with attached attribute data. This compact representation is composed of multiple levels of detail that can be progressively transmitted and displayed. The global topology, which is the number of holes and connected components, can be flexibly changed among successive levels while still achieving guaranteed size of the coarsest level mesh for very complex models. The flexibility in our encoding scheme also allows topology preserving progressivity.
Real-time visualization of scalably large collections of heterogeneous objects
Authors: Douglass Davis, William Ribarsky, Tian-Yue Jiang, Nickolas Faust, Sean Ho
Published at Vis, 1999

This paper presents results for real-time visualization of out-of-core collections of 3D objects. This is a significant extension of previous methods and shows the generality of hierarchical paging procedures applied both to global terrain and any objects that reside on it. Applied to buildings, the procedure shows the effectiveness of using a screen-based paging and display criterion within a hierarchical framework. The results demonstrate that the method is scalable since it is able to handle multiple collections of buildings (e.g., cities) placed around the earth with full interactivity and without extensive memory load. Further the method shows efficient handling of culling and is applicable to larger, extended collections of buildings. Finally, the method shows that levels of detail can be incorporated to provide improved detail management.
Rendering on a budget: a framework for time-critical rendering
Authors: James T. Klosowski, Cláudio T. Silva
Published at Vis, 1999

We present a technique for optimizing the rendering of high-depth complexity scenes. Prioritized-Layered Projection (PLP) does this by rendering an estimation of the visible set. The novelty in our work lies in the fact that we do not explicitly compute visible sets. Instead, our work is based on computing on demand a priority order for the polygons that maximizes the likelihood of rendering visible polygons before occluded ones for any given scene. Given a fixed budget, e.g. time or number of triangles, our rendering algorithm makes sure to render geometry, respecting the computed priority. There are two main steps to our technique: (1) an occupancy based tessellation of space; and (2) a solidity based traversal algorithm. PLP works by computing an occupancy based tessellation of space, which tends to have smaller cells where there are more geometric primitives, e.g., polygons. In this spatial tessellation, each cell is assigned a solidity value, which is directly proportional to its likelihood of occluding other cells. In its simplest form, a cell's solidity value is directly proportional to the number of polygons contained within it. During our traversal algorithm, cells are marked for projection, and the geometric primitives contained within them actually rendered. The traversal algorithm makes use of the cells' solidity, and other view-dependent information to determine the ordering in which to project cells. By tailoring the traversal algorithm to the occupancy based tessellation, we can achieve very good frame rates with low preprocessing and rendering costs. We describe our technique and its implementation in detail. We also provide experimental evidence of its performance and briefly discuss extensions of our algorithm.
Simplified representation of vector fields
Authors: Alexandru C. Telea, Jarke J. van Wijk
Published at Vis, 1999

Vector field visualization remains a difficult task. Many local and global visualization methods for vector fields such as flow data exist, but they usually require extensive user experience on setting the visualization parameters in order to produce images communicating the desired insight. We present a visualization method that produces simplified but suggestive images of the vector field automatically, based on a hierarchical clustering of the input data. The resulting clusters are then visualized with straight or curved arrow icons. The presented method has a few parameters with which users can produce various simplified vector field visualizations that communicate different insights on the vector data.
Skip Strips: maintaining triangle strips for view-dependent rendering
Authors: Jihad El-Sana, Elvir Azanli, Amitabh Varshney
Published at Vis, 1999

View-dependent simplification has emerged as a powerful tool for graphics acceleration in visualization of complex environments. However, view-dependent simplification techniques have not been able to take full advantage of the underlying graphics hardware. Specifically, triangle strips are a widely used hardware-supported mechanism to compactly represent and efficiently render static triangle meshes. However, in a view-dependent framework, the triangle mesh connectivity changes at every frame, making it difficult to use triangle strips. We present a novel data structure, Skip Strip, that efficiently maintains triangle strips during such view-dependent changes. A Skip Strip stores the vertex hierarchy nodes in a skip-list-like manner with path compression. We anticipate that Skip Strips will provide a road map to combine rendering acceleration techniques for static datasets, typical of retained-mode graphics applications, with those for dynamic datasets found in immediate-mode applications.
Spiraling Edge: fast surface reconstruction from partially organized sample points
Authors: Patricia Crossno, Edward Angel
Published at Vis, 1999

Many applications produce three-dimensional points that must be further processed to generate a surface. Surface reconstruction algorithms that start with a set of unorganized points are extremely time-consuming. Sometimes however, points are generated such that there is additional information available to the reconstruction algorithm. We present Spiraling Edge, a specialized algorithm for surface reconstruction that is three orders of magnitude faster than algorithms for the general case. In addition to sample point locations, our algorithm starts with normal information and knowledge of each point's neighbors. Our algorithm produces a localized approximation to the surface by creating a star-shaped triangulation between a point and a subset of its nearest neighbors. This surface patch is extended by locally triangulating each of the points along the edge of the patch. As each edge point is triangulated, it is removed from the edge and new edge points along the patch's edge are inserted in its place. The updated edge spirals out over the surface until the edge encounters a surface boundary and stops growing in that direction, or until the edge reduces to a small hole that is filled by the final triangle.
Splatting without the blur
Authors: Klaus Mueller 0001, Torsten Möller, Roger Crawfis
Published at Vis, 1999

Splatting is a volume rendering algorithm that combines efficient volume projection with a sparse data representation. Only voxels that have values inside the iso-range need to be considered, and these voxels can be projected via efficient rasterization schemes. In splatting, each projected voxel is represented as a radially symmetric interpolation kernel, equivalent to a fuzzy ball. Projecting such a basis function leaves a fuzzy impression, called a footprint or splat, on the screen. Splatting traditionally classifies and shades the voxels prior to projection, and thus each voxel footprint is weighted by the assigned voxel color and opacity. Projecting these fuzzy color balls provides a uniform screen image for homogeneous object regions, but leads to a blurry appearance of object edges. The latter is clearly undesirable, especially when the view is zoomed on the object. In this work, we manipulate the rendering pipeline of splatting by performing the classification and shading process after the voxels have been projected onto the screen. In this way volume contributions outside the iso-range never affect the image. Since shading requires gradients, we not only splat the density volume, using regular splats, but we also project the gradient volume, using gradient splats. However alternative to gradient splats, we can also compute the gradients on the projection plane using central differencing. This latter scheme cuts the number of footprint rasterization by a factor of four since only the voxel densities have to be projected.
Structured spatial domain image and data comparison metrics
Authors: Nivedita Sahasrabudhe, John West 0001, Raghu Machiraju, Mark Janus
Published at Vis, 1999

Often, images or datasets have to be compared to facilitate choices of visualization and simulation parameters respectively. Common comparison techniques include side-by-side viewing and juxtaposition, in order to facilitate visual verification of verisimilitude. We propose quantitative techniques which accentuate differences in images and datasets. The comparison is enabled through a collection of partial metrics which, essentially, measure the lack of correlation between the datasets or images being compared. That is, they attempt to expose and measure the extent of the inherent structures in the difference between images or datasets. Besides yielding numerical attributes, the metrics also produce images which can visually highlight differences. Our metrics are simple to compute and operate in the spatial domain. We demonstrate the effectiveness of our metrics through examples for comparing images and datasets.
Tensorlines: Advection-Diffusion based Propagation through Diffusion Tensor Fields
Authors: David M. Weinstein, Gordon L. Kindlmann, Eric C. Lundberg
Published at Vis, 1999

Tracking linear features through tensor field datasets is an open research problem with widespread utility in medical and engineering disciplines. Existing tracking methods, which consider only the preferred local diffusion direction as they propagate, fail to accurately follow features as they enter regions of local complexity. This shortcoming is a result of partial voluming; that is, voxels in these regions often contain contributions from multiple features. These combined contributions result in ambiguities when deciding local primary feature orientation based solely on the preferred diffusion direction. We introduce a novel feature extraction method which we term tensorline propagation. Our method resolves the above ambiguity by incorporating information about the nearby orientation of the feature, as well as the anisotropic classification of the local tensor. The nearby orientation information is added in the spirit of an advection term in a standard diffusion based propagation technique, and has the effect of stabilizing the tracking. To demonstrate the efficacy of tensorlines, we apply this method to the neuroscience problem of tracking white-matter bundles within the brain.
Tetrahedral Mesh Compression with the Cut-Border Machine
Authors: Stefan Gumhold, Stefan Guthe, Wolfgang Straßer
Published at Vis, 1999

In recent years, substantial progress has been achieved in the area of volume visualization on irregular grids, which is mainly based on tetrahedral meshes. Even moderately fine tetrahedral meshes consume several mega-bytes of storage. For archivation and transmission compression algorithms are essential. In scientific applications lossless compression schemes are of primary interest. This paper introduces a new lossless compression scheme for the connectivity of tetrahedral meshes. Our technique can handle all tetrahedral meshes in three dimensional euclidean space even with non manifold border. We present compression and decompression algorithms which consume for reasonable meshes linear time in the number of tetrahedra. The connectivity is compressed to less than 2.4 bits per tetrahedron for all measured meshes. Thus a tetrahedral mesh can almost be reduced to the vertex coordinates, which consume in a common representation about one quarter of the total storage space. We complete our work with solutions for the compression of vertex coordinates and additional attributes, which might be attached to the mesh.
The "Parallel Vectors" operator-a vector field visualization primitive
Authors: Ronald Peikert, Martin Roth
Published at Vis, 1999

We propose an elementary operation on a pair of vector fields as a building block for defining and computing global line-type features of vector or scalar fields. While usual feature definitions often are procedural and therefore implicit, our operator allows precise mathematical definitions. It can serve as a basis for comparing feature definitions and for reuse of algorithms and implementations. Applications focus on vortex core methods.
Time-critical Multiresolution Scene Rendering
Authors: Enrico Gobbetti, Eric Bouvier
Published at Vis, 1999

We describe a framework for time-critical rendering of graphics scenes composed of a large number of objects having complex geometric descriptions. Our technique relies upon a scene description in which objects are represented as multiresolution meshes. We perform a constrained optimization at each frame to choose the resolution of each potentially visible object that generates the best quality image while meeting timing constraints. The technique provides smooth level-of-detail control and aims at guaranteeing a uniform, bounded frame rate even for widely changing viewing conditions. The optimization algorithm is independent from the particular data structure used to represent multiresolution meshes. The only requirements are the ability to represent a mesh with an arbitrary number of triangles and to traverse a mesh structure at an arbitrary resolution in a short predictable time. A data structure satisfying these criteria is described and experimental results are discussed.
Visual debugging of visualization software: a case study for particle systems
Authors: Patricia Crossno, Edward Angel
Published at Vis, 1999

Visualization systems are complex dynamic software systems. Debugging such systems is difficult using conventional debuggers because the programmer must try to imagine the three-dimensional geometry based on a list of positions and attributes. In addition, the programmer must be able to mentally animate changes in those positions and attributes to grasp dynamic behaviors within the algorithm. We show that representing geometry, attributes, and relationships graphically permits visual pattern recognition skills to be applied to the debugging problem. The particular application is a particle system used for isosurface extraction from volumetric data. Coloring particles based on individual attributes is especially helpful when these colorings are viewed as animations over successive iterations in the program. Although we describe a particular application, the types of tools that we discuss can be applied to a variety of problems.
Visualization needs more visual design!
Authors: J. Edward Swan II, Theresa-Marie Rhyne, David H. Laidlaw, Tamara Munzner, Victoria Interrante
Published at Vis, 1999

During the past decade, much work in the field of Visualization has resulted from the efforts of at least two groups of researchers. One group has focused on rendering techniques for visualization technologies (e.g. volume rendering), while another group has focused on designing visual elements for the purpose of visualizing a certain application domain (e.g. streamlines to visualize flow fields, as well as most applications in Information Visualization). This panel session brings together researchers from both groups. Together we will argue that utilizing visual design is difficult ,but important for visualization, and we need to work harder to tap into the many centuries of design knowledge that exists in fields such as art, music, theater, cartography, architecture, and so forth. Some of the issues we will explore include:
Visualization of conflicts and resolutions in a "Free Flight" scenario
Authors: Ronald T. Azuma, Howard Neely, Michael J. Daily, Mario Correa
Published at Vis, 1999

"Free Flight" will change today's air traffic control system by giving pilots increased flexibility to choose and modify their routes in real time, reducing costs and increasing system capacity. This increased flexibility comes at the price of increased complexity. If Free Flight is to become a reality, future air traffic controllers, pilots, and airline managers will require new conflict detection, resolution and visualization decision support tools. The paper describes a testbed system for building and evaluating such tools, including its current capabilities, lessons we learned and feedback received from expert users. The visualization system provides an overall plan view supplemented with a detailed perspective view, allowing a user to examine highlighted conflicts and select from a list of proposed solutions, as the scenario runs in real time. Future steps needed to improve this system are described.