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Visualization and Computer Graphics, IEEE Transactions on

Issue 4 • Date Dec. 1995

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Displaying Results 1 - 8 of 8
  • 1995 Index IEEE Transactions on Visualization and Computer Graphics Vol. 1

    Publication Year: 1995
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    Freely Available from IEEE
  • Hybrid scan-conversion of circles

    Publication Year: 1995 , Page(s): 311 - 318
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    Conventional algorithms for scan-conversion of circles select one pixel in each iteration. Run-length slice circle algorithms have therefore been suggested. These algorithms determine a run of pixels in each iteration. The speed of scan-conversion is therefore increased due to I/O. A hybrid approach to the scan-conversion of circles is presented. The new approach combines the advantages of the two methods into a hybrid algorithm. Speedup is achieved in the hybrid algorithm not only due to the reduction in the number of I/O operations, but also due to a reduction in the number of arithmetic operations View full abstract»

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  • Modeling and visualization of knitwear

    Publication Year: 1995 , Page(s): 302 - 310
    Cited by:  Papers (11)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1420 KB)  

    Visualization and modeling of textile materials has already been investigated in detail in the computer graphics literature. Most of the work, however, concentrates on woven fabrics. We present a novel approach to the modeling and rendering of knitwear. After the topological specification of a knitting pattern a subdivision into basic elements is done. The yarn microstructure within basic elements is approximated by volume data sets. The repetitive structure of knitted fabrics allows an efficient rendering technique. Resulting images are given that demonstrate the feasibility of our approach View full abstract»

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  • Specification by-example of virtual agents behavior

    Publication Year: 1995 , Page(s): 350 - 360
    Cited by:  Papers (7)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1456 KB)  

    The development of virtual agents running within graphic environments which emulate real-life contexts may largely benefit from the use of visual specification by-example. To support this specification, the development system must be able to interpret the examples and cast their underlying rules into an internal representation language. This language must find a suitable trade-off among a number of contrasting requirements regarding expressiveness, automatic executability, and suitability to the automatic representation of rules deriving from the analysis of examples. A language is presented which attains this trade-off by combining together an operational and a declarative fragment to separately represent the autonomous execution of each individual agent and its interaction with the environment, respectively. While the declarative part permits to capture interaction rules emerging from specification examples, the operational part supports the automatic execution in the operation of the virtual environment. A system is presented which embeds this language within a visual shell to support a behavioral training in which the animation rules of virtual agents are defined through visual examples View full abstract»

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  • Exploiting triangulated surface extraction using tetrahedral decomposition

    Publication Year: 1995 , Page(s): 328 - 342
    Cited by:  Papers (51)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2476 KB)  

    Beginning with digitized volumetric data, we wish to rapidly and efficiently extract and represent surfaces defined as isosurfaces in the interpolated data. The Marching Cubes algorithm is a standard approach to this problem. We instead perform a decomposition of each 8-cell associated with a voxel into five tetrahedra. We guarantee the resulting surface representation to be closed and oriented, defined by a valid triangulation of the surface of the body, which in turn is presented as a collection of tetrahedra. The entire surface is “wrapped” by a collection of triangles, which form a graph structure, and where each triangle is contained within a single tetrahedron. The representation is similar to the homology theory that uses simplices embedded in a manifold to define a closed curve within each tetrahedron. We introduce data structures based upon a new encoding of the tetrahedra that are at least four times more compact than the standard data structures using vertices and triangles. For parallel computing and improved cache performance, the vertex information is stored local to the tetrahedra. We can distribute the vertices in such a way that no tetrahedron ever contains more than one vertex, We give methods to evaluate surface curvatures and principal directions at each vertex, whenever these quantities are defined. Finally, we outline a method for simplifying the surface, that is reducing the vertex count while preserving the geometry. We compare the characteristics of our methods with an 8-cell based method, and show results of surface extractions from CT-scans and MR-scans at full resolution View full abstract»

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  • A multiscale model for structure-based volume rendering

    Publication Year: 1995 , Page(s): 291 - 301
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1228 KB)  

    A scalar volume V={(x,f(x))|x∈R} is described by a function f(x) defined over some region R of the 3D space. We present a simple technique for rendering multiscale interval sets of the form Is (a,b)={(x,fs(x))|a⩽gs(x)⩽b}, where a and b are either real numbers or infinities, and fs(x) is a smoothed version of f(x). At each scale s, the constraint a⩽gs (x)⩽b identifies a subvolume in which the most significant variations of V are found. We use a dyadic wavelet transform to construct gs(x) from f(x) and derive subvolumes with the following attractive properties: 1) the information contained in the subvolumes are sufficient for reconstructing the entire V; and 2) the shapes of the subvolumes provide a hierarchical description of the geometric structures of V. Numerically, the reconstruction in 1) is only an approximation, but it is visually accurate as errors reside at fine scales where our visual sensitivity is not so acute. We triangulate interval sets as α-shapes, which can be efficiently rendered as semi-transparent clouds. Because interval sets are extracted in the object space, their visual display can respond to changes of the view point or transfer function quite fast. The result is a volume rendering technique that provides faster, more effective user interaction with practically no loss of information from the original data. The hierarchical nature of multiscale interval sets also makes it easier to understand the usual complicated structures in scalar volumes View full abstract»

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  • Octree-R: an adaptive octree for efficient ray tracing

    Publication Year: 1995 , Page(s): 343 - 349
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1416 KB)  

    Ray tracing requires many ray-object intersection tests. A way of reducing the number of ray-object intersection tests is to subdivide the space occupied by objects into many nonoverlapping subregions, called voxels, and to construct an octree for the subdivided space. We propose the Octree-R, an octree-variant data structure for efficient ray tracing. The algorithm for constructing the Octree-R first estimates the number of ray-object intersection tests. Then, it partitions the space along the plane that minimizes the estimated number of ray-object intersection tests. We present the results of experiments for verifying the effectiveness of the Octree-R. In the experiment, the Octree-R provides a 4% to 47% performance gain over the conventional octree. The result shows the more skewed the object distribution (as is typical for real data), the more performance gain the Octree-R achieves View full abstract»

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  • Automatic isosurface propagation using an extrema graph and sorted boundary cell lists

    Publication Year: 1995 , Page(s): 319 - 327
    Cited by:  Papers (38)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    A high-performance algorithm for generating isosurfaces is presented. In our method, guides to searching for cells intersected by an isosurface are generated as a pre-process. These guides are two kinds of cell lists: an extrema graph, and sorted lists of boundary cells. In an extrema graph, extremum points are connected by arcs, and each arc has a list of cells through which it passes. At the same time, all boundary cells are sorted according to their minimum and maximum values, and two sorted lists are then generated. Isosurfaces are generated by visiting adjacent intersected cells in order. Here, the starting cells for this process are found by searching in an extrema graph and in sorted boundary cell lists. In this process, isosurfaces appear to propagate themselves. Our algorithm is efficient, since it visits only cells that are intersected by an isosurface and cells whose IDs are included in the guides. It is especially efficient when many isosurfaces are interactively generated in a huge volume. Some benchmark tests described in this paper show the efficiency of the algorithm 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