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GVU Technical Report Series

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Now showing 1 - 10 of 309
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    Repo: An Interpreted Language for Exploratory Programming of Highly Interactive, Distributed Applications
    (Georgia Institute of Technology, 1999) MacIntyre, Blair
    In this paper we present Repo, an interpreted language for exploratory programming of distributed interactive applications. Repo is based on Obliq, a distributed language that supports client-server distribution semantics of all data items (objects, arrays and variables). Repo extends Obliqs type system uniformly so that all its data items can also be distributed with unsynchronized or synchronized replication semantics, both of which are needed by highly interactive applications. Since all of Repos data items can take on any distribution semantic and be mixed in arbitrary ways, a wide range of interesting data structures can be developed in Repo in a straightforward manner. Since Repo allows distributed applications to be developed in a few lines of interpreted code, it turns out to be an excellent language for exploratory programming of distributed interactive applications. We discuss the design and implementation of Repo, and provide illustrative examples taken from prototypes build using it.
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    Efficient Ray Intersection for Visualization and Navigation of Global Terrain using Spheroidal Height-Augmented Quadtrees
    (Georgia Institute of Technology, 1999) Wartell, Zachary Justin ; Ribarsky, William ; Hodges, Larry F.
    We present an algorithm for efficiently computing ray intersections with multi-resolution global terrain partitioned by spheroidal height-augmented quadtrees. While previous methods support terrain defined on a Cartesian coordinate system, our methods support terrain defined on a two-parameter ellipsoidal coordinate system. This curvilinear system is necessary for an accurate model of global terrain. Supporting multi-resolution terrain and quadtrees on this curvilinear coordinate system raises a surprising number of complications. We describe the complexities and present solutions. The final algorithm is suited for interactive terrain selection, collision detection and simple LOS (line-of-site) queries on global terrain.
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    Discovery Visualization and Visual Data Mining
    (Georgia Institute of Technology, 1999) Ribarsky, William ; Katz, Jochen ; Jiang, Frank ; Holland, Aubrey
    This paper describes discovery visualization, a new visual data mining approach that has as a key element the heightened awareness of the user by the machine. Discovery visualization promotes the concept of continuous interaction with constant feedback between man and machine and constant unfolding of the data. It does this by providing a combination of automated response and user selection to achieve and sustain animated action while the user explores time-dependent data. The process begins by automatically generating an overview using a fast clustering approach, where the clusters are then followed as time-dependent features. Discovery visualization is applied to both test data and real application data. The results show that the method is accurate and scalable, and it offers a straightforward, error-based process for improvement of accuracy.
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    Matchmaker: Manifold Breps for Non-manifold r-sets
    (Georgia Institute of Technology, 1999) Rossignac, Jarek ; Cardoze, David Enrique Fabrega
    Many solid modeling construction techniques produce non-manifold r-sets (solids). With each non-manifold model N we can associate a family of manifold solid models that are infinitely close to N in the geometric sense. For polyhedral solids, each non-manifold edge of N with 2k incident faces will be replicated k times in any manifold model M of that family. Furthermore, some non-manifold vertices of N must also be replicated in M, possibly several times. M can be obtained by defining, in N, a single adjacent face TA(E,F) for each pair (E,F) that combines an edge E and an incident face F. The adjacency relation satisfies TA(E,TA(E,F))=F. The choice of the map A defines which vertices of N must be replicated in M and how many times. The resulting manifold representation of a non-manifold solid may be encoded using simpler and more compact data-structures, especially for triangulated model, and leads to simpler and more efficient algorithms, when it is used instead of a non-manifold representation for a variety of tasks, such as simplification, compression, interference detection or rendering. Most choices of the map A lead to invalid (self-intersecting) boundaries and to unnecessary vertex replications for M. We propose an efficient algorithm, called Matchmaker, which computes a map A, such that there exists an infinitely small perturbation of the vertices and edges of M that produces a valid (non self-intersecting) boundary of a manifold solid. Furthermore, our approach avoids most unnecessary vertex replications.
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    The Conference Assistant: Combining Context-Awareness with Wearable Computing
    (Georgia Institute of Technology, 1999) Dey, Anind K. ; Futakawa, Masayasu ; Salber, Daniel ; Abowd, Gregory D.
    We describe the Conference Assistant, a prototype mobile, context-aware application that assists conference attendees. We discuss the strong relationship between context-awareness and wearable computing and apply this relationship in the Conference Assistant. The application uses a wide variety of context and enhances user interactions with both the environment and other users. We describe how the application is used and the context-aware architecture on which it was based.
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    Image-Driven Simplification
    (Georgia Institute of Technology, 1999) Lindstrom, Peter ; Turk, Greg
    We introduce the notion of image-driven simplification, a framework that uses images to decide which portions of a model to simplify. This is a departure from approaches that make polygonal simplification decisions based on geometry. As with many methods, we use the edge collapse operator to make incremental changes to a model. Unique to our approach, however, is the use of comparisons between images of the original model against those of a simplified model to determine the cost of an edge collapse. We use common graphics rendering hardware to accelerate the creation of the required images. As expected, this method produces models that are close to the original model according to image differences. Perhaps more surprising, however, is that the method yields models that have high geometric fidelity as well. Our approach also solves the quandary of how to weight the geometric distance versus appearance properties such as normals, color and texture. All of these tradeoffs are balanced by the image metric. Benefits of this approach include high fidelity silhouettes, extreme simplification of hidden portions of a model, attention to shading interpolation effects, and simplification that is sensitive to the content of a texture. In order to better preserve the appearance of textured models, we introduce a novel technique for assigning texture coordinates to the new vertices of the mesh. This method is based on a geometric heuristic that can be integrated with any edge collapse algorithm to produce high quality textured surfaces.
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    Connectivity Compression for Irregular Quadrilateral Meshes
    (Georgia Institute of Technology, 1999) King, Davis ; Szymczak, Andrzej ; Rossignac, Jarek
    Many 3D models used in engineering, scientific, and visualization applications are represented by an irregular mesh of bounding quadrilaterals. We propose a scheme for compressing the connectivity of irregular quadrilateral meshes in 0.26-1.7 bits/quad, a 25-45% savings over randomly splitting quads into triangles and applying triangle mesh compression. Our approach is an extension of the Edgebreaker compression approach and of the Wrap&Zip decompression technique.
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    Variational Implicit Surfaces
    (Georgia Institute of Technology, 1999) Turk, Greg ; O'Brien, James F.
    We introduce a new method of creating smooth implicit surfaces of arbitrary manifold topology. These surfaces are described by specifying locations in 3D through which the surface should pass, and also identifying locations that are interior or exterior to the surface. A 3D implicit function is created from these constraints using a variational scattered data interpolation approach. We call the iso-surface of this function a \emph{variational implicit surface}. Like other implicit surface descriptions, these surfaces can be used for CSG and interference detection, may be interactively manipulated, are readily approximated by polygonal tilings, and are easy to ray trace. A key strength is that variational implicit surfaces allow the direct specification of both the location of points on the surface and surface normals. These are two important manipulation techniques that are difficult to achieve using other implicit surface representations such as sums of spherical or ellipsoidal Gaussian functions (``blobbies''). We show that these properties make variational implicit surfaces particularly attractive for interactive sculpting using the particle sampling technique introduced by Witkin and Heckbert in~\cite{Witkin}. Our formulation also yields a simple method for converting a polygonal model to a smooth implicit model.
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    CWIC: Using Images to Passively Browse the Web
    (Georgia Institute of Technology, 1999) Brown, Quasedra Y. ; McCrickard, D. Scott
    The World Wide Web has emerged as one of the most widely available and diverse information sources of all time, yet the options for accessing this information are limited. This paper introduces CWIC, the Continuous Web Image Collector, a system that automatically traverses selected Web sites collecting and analyzing images, then presents them to the user using one of a variety of available display mechanisms and layouts. The CWIC mechanisms were chosen because they present the images in a non-intrusive method: the goal is to allow users to stay abreast of Web information while continuing with more important tasks. The various display layouts allow the user to select one that will provide them with as little interruptions as possible yet will be aesthetically pleasing.
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    Tracking and Modifying Upper-Body Human Mortion Data with Dynamic Simulation
    (Georgia Institute of Technology, 1999) Zordan, Victor B. ; Hodgins, Jessica K.
    Character animations generated with motion capture data contain many of the stylistic details seen in human motion while those generated with simulation are physically realistic for the dynamic parameters of the character. We combine these two approaches by tracking and modifying human motion capture data using dynamic simulation and constraints. The tracking system generates motion that is appropriate for the graphical character while maintaining characteristics of the original human motion. The system imposes contact and task constraints to add dynamic impacts for interactions with the environment and to modify motions at the behavior level. The system is able to edit motion data to account for changes in characters and the environment as well as create smooth transitions between motion capture sequences. We demonstrate the power of combining these two approaches by tracking data for a variety of upper-body motions and by animating models with differing kinematic and dynamic parameters.