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Visualization and Computer Graphics, IEEE Transactions on

Issue 1 • Date Jan-Mar 1997

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Displaying Results 1 - 8 of 8
  • Virtual Data Visualizer

    Publication Year: 1997 , Page(s): 65 - 74
    Cited by:  Papers (12)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (872 KB)  

    Te authors present the Virtual Data Visualizer, a highly interactive, immersive environment for visualizing and analyzing data. VDV is a set of tools for exploratory data visualization that does not focus on just one type of application. It employs a data organization with data arranged hierarchically in classes that can be modified by the user within the virtual environment. The class structure is the basis for bindings or mappings between data variables and glyph elements, which the user can make, change, or remove. The binding operation also has a set of defaults so that the user can quickly display the data. The VDV requires a user interface that is fairly complicated for a virtual environment. They have taken the approach that a combination of more-or-less traditional menus and more direct means of icon manipulation will do the job. This work shows that a useful interface and set of tools can be built. Controls in VDV include a panel for controlling animation of the data and zooming in and out. Tools include a workbench for changing the glyphs and setting glyph/variable ranges and a boundary tool for defining new classes spatially View full abstract»

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  • On compatible star decompositions of simple polygons

    Publication Year: 1997 , Page(s): 87 - 95
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    The authors introduce the notion of compatible star decompositions of simple polygons. In general, given two polygons with a correspondence between their vertices, two polygonal decompositions of the two polygons are said to be compatible if there exists a one-to-one mapping between them such that the corresponding pieces are defined by corresponding vertices. For compatible star decompositions, they also require correspondence between star points of the star pieces. Compatible star decompositions have applications in computer animation and shape representation and analysis. They present two algorithms for constructing compatible star decompositions of two simple polygons. The first algorithm is optimal in the number of pieces in the decomposition, providing that such a decomposition exists without adding Steiner vertices. The second algorithm constructs compatible star decompositions with Steiner vertices, which are not minimal in the number of pieces but are asymptotically worst-case optimal in this number and in the number of added Steiner vertices. They prove that some pairs of polygons require Ω(n2) pieces, and that the decompositions computed by the second algorithm possess no more than O(n2) pieces. In addition to the contributions regarding compatible star decompositions, the paper also corrects an error in the only previously published polynomial algorithm for constructing a minimal star decomposition of a simple polygon, an error which might lead to a nonminimal decomposition View full abstract»

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  • Error and complexity of random walk Monte Carlo radiosity

    Publication Year: 1997 , Page(s): 23 - 38
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    The author studies the error and complexity of the discrete random walk Monte Carlo technique for radiosity, using both the shooting and gathering methods. The author shows that the shooting method exhibits a lower complexity than the gathering one, and under some constraints, it has a linear complexity. This is an improvement over a previous result that pointed to an O(n log n) complexity. The author gives and compares three unbiased estimators for each method, and obtains closed forms and bounds for their variances. The author also bounds the expected value of the mean square error (MSE). Some of the results obtained are also shown to be valid for the nondiscrete gathering case. The author also gives bounds for the variances and MSE for the infinite path length estimators; these bounds might be useful in the study of biased estimators resulting from cutting off the infinite path View full abstract»

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  • The discrete analytical hyperspheres

    Publication Year: 1997 , Page(s): 75 - 86
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    An analytical definition of a discrete hypersphere with arbitrary center, radius, and thickness in dimension n is introduced. The new discrete hypersphere is called a discrete analytical hypersphere. The hypersphere has important original properties including exact point localization, space tiling, k-separation, etc. These properties are almost obvious with this new discrete analytical definition contrary to the classical approaches based on digitization schemes. The analytically defined circle is compared to Pham's (1992) classically defined circle. Efficient incremental circle and hypersphere generation algorithms are provided View full abstract»

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  • Multipole expansion of the light vector

    Publication Year: 1997 , Page(s): 12 - 22
    Cited by:  Papers (5)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Computing the light field due to an area light source remains an interesting problem in computer graphics. The paper presents a series approximation of the light field due to an unoccluded area source, by expanding the light field in spherical harmonics. The source can be nonuniform and need not be a planar polygon. The resulting formulas give expressions whose cost and accuracy can be chosen between the exact and expensive Lambertian solution for a diffuse polygon, and the fast but inexact method of replacing the area source by a point source of equal power. The formulas break the computation of the light vector into two phases: the first phase represents the light source's shape and brightness with numerical coefficients, and the second uses these coefficients to compute the light field at arbitrary locations. The author examines the accuracy of the formulas for spherical and rectangular Lambertian sources, and applies them to obtain light gradients. The author also shows how to use the formulas to estimate light from uniform polygonal sources, sources with polynomially varying radiosity, and luminous textures View full abstract»

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  • Incremental algorithms for collision detection between polygonal models

    Publication Year: 1997 , Page(s): 51 - 64
    Cited by:  Papers (55)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    Fast and accurate collision detection between general polygonal models is a fundamental problem in physically based and geometric modeling, robotics, animation, and computer-simulated environments. Most earlier collision detection algorithms are either restricted to a class of models (such as convex polytopes) or are not fast enough for practical applications. The authors present an incremental algorithm for collision detection between general polygonal models in dynamic environments. The algorithm combines a hierarchical representation with incremental computation to rapidly detect collisions. It makes use of coherence between successive instances to efficiently determine the number of object features interacting. For each pair of objects, it tracks the closest features between them on their respective convex hulls. It detects the objects' penetration using pseudo internal Voronoi cells and constructs the penetration region, thus identifying the regions of contact on the convex hulls. The features associated with these regions are represented in a precomputed hierarchy. The algorithm uses a coherence based approach to quickly traverse the precomputed hierarchy and check for possible collisions between the features. They highlight its performance on different applications View full abstract»

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  • Animation of deformable models using implicit surfaces

    Publication Year: 1997 , Page(s): 39 - 50
    Cited by:  Papers (30)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1876 KB)  

    The paper presents a general approach for designing and animating complex deformable models with implicit surfaces. Implicit surfaces are introduced as an extra layer coating any kind of structure that moves and deforms over time. Offering a compact definition of a smooth surface around an object, they provide an efficient collision detection mechanism. The implicit layer deforms in order to generate exact contact surfaces between colliding bodies. A simple physically based model approximating elastic behavior is then used for computing collision response. The implicit formulation also eases the control of the object's volume with a new method based on local controllers. We present two different applications that illustrate the benefits of these techniques. First, the animation of simple characters made of articulated skeletons coated with implicit flesh exploits the compactness and enhanced control of the model. The second builds on the specific properties of implicit surfaces for modeling soft inelastic substances capable of separation and fusion that maintain a constant volume when animated View full abstract»

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  • The topology of symmetric, second-order 3D tensor fields

    Publication Year: 1997 , Page(s): 1 - 11
    Cited by:  Papers (26)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2480 KB)  

    The authors study the topology of symmetric, second-order tensor fields. The results of the study can be readily extended to include general tensor fields through linear combination of symmetric tensor fields and vector fields. The goal is to represent their complex structure by a simple set of carefully chosen points, lines, and surfaces analogous to approaches in vector field topology. They extract topological skeletons of the eigenvector fields and use them for a compact, comprehensive description of the tensor field. Their approach is based on the premise: “analyze, then visualize”. The basic constituents of tensor topology are the degenerate points, or points where eigenvalues are equal to each other. Degenerate points play a similar role as critical points in vector fields. In tensor fields they identify two kinds of elementary degenerate points, which they call wedge points and trisector points. They can combine to form more familiar singularities-such as saddles, nodes, centers, or foci. However, these are generally unstable structures in tensor fields. Based on the notions developed for 2D tensor fields, they extend the theory to include 3D degenerate points. Examples are given on the use of tensor field topology for the interpretation of physical systems View full abstract»

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Aims & Scope

Visualization techniques and methodologies; visualization systems and software; volume visualization; flow visualization; multivariate visualization; modeling and surfaces; rendering; animation; user interfaces; visual progranuning; applications.

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Meet Our Editors

Editor-in-Chief
Leila De Floriani
Department of Computer Science, Bioengineering, Robotics and Systems Engineering
University of Genova
16146 Genova (Italy)
ldf4tvcg@umiacs.umd.edu