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Visualization and Computer Graphics, IEEE Transactions on

Issue 3 • Date Jul-Sep 2000

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Displaying Results 1 - 6 of 6
  • Dynamic modeling of butterfly subdivision surfaces

    Publication Year: 2000 , Page(s): 265 - 287
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1588 KB)  

    The authors develop integrated techniques that unify physics based modeling with geometric subdivision methodology and present a scheme for dynamic manipulation of the smooth limit surface generated by the (modified) butterfly scheme using physics based “force” tools. This procedure based surface model obtained through butterfly subdivision does not have a closed form analytic formulation (unlike other well known spline based models), and hence poses challenging problems to incorporate mass and damping distributions, internal deformation energy, forces, and other physical quantities required to develop a physics based model. Our primary contributions to computer graphics and geometric modeling include: (1) a new hierarchical formulation for locally parameterizing the butterfly subdivision surface over its initial control polyhedron, (2) formulation of dynamic butterfly subdivision surface as a set of novel finite elements, and (3) approximation of this new type of finite elements by a collection of existing finite elements subject to implicit geometric constraints. Our new physics based model can be sculpted directly by applying synthesized forces and its equilibrium is characterized by the minimum of a deformation energy subject to the imposed constraints. We demonstrate that this novel dynamic framework not only provides a direct and natural means of manipulating geometric shapes, but also facilitates hierarchical shape and nonrigid motion estimation from large range and volumetric data sets using very few degrees of freedom (control vertices that define the initial polyhedron) View full abstract»

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  • Fast ray-tracing of rectilinear volume data using distance transforms

    Publication Year: 2000 , Page(s): 236 - 252
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2004 KB)  

    The paper discusses and experimentally compares distance based acceleration algorithms for ray tracing of volumetric data with an emphasis on the Chessboard Distance (CD) voxel traversal. The acceleration of this class of algorithms is achieved by skipping empty macro regions, which are defined for each background voxel of the volume. Background voxels are labeled in a preprocessing phase by a value, defining the macro region size, which is equal to the voxel distance to the nearest foreground voxel. The CD algorithm exploits the chessboard distance and defines the ray as a nonuniform sequence of samples positioned at voxel faces. This feature assures that no foreground voxels are missed during the scene traversal. Further, due to parallelepipedal shape of the macro region, it supports accelerated visualization of cubic, regular, and rectilinear grids. The CD algorithm is suitable for all modifications of the ray tracing/ray casting techniques being used in volume visualization and volume graphics. However, when used for rendering based on local surface interpolation, it also enables fast search of intersections between rays and the interpolated surface, further improving speed of the process View full abstract»

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  • Accessibility analysis using computer graphics hardware

    Publication Year: 2000 , Page(s): 208 - 219
    Cited by:  Papers (16)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (972 KB)  

    Analyzing the accessibility of an object's surface to probes or tools is important for many planning and programming tasks that involve spatial reasoning and arise in robotics and automation. The paper presents novel and efficient algorithms for computing accessible directions for tactile probes used in 3D digitization with Coordinate Measuring Machines. The algorithms are executed in standard computer graphics hardware. They are a nonobvious application of rendering hardware to scientific and technological areas beyond computer graphics View full abstract»

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  • A perceptually-driven parallel algorithm for efficient radiosity simulation

    Publication Year: 2000 , Page(s): 220 - 235
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1800 KB)  

    The authors describe a novel algorithm for computing view-independent finite element radiosity solutions on distributed shared memory parallel architectures. Our approach is based on the notion of a subiteration being the transfer of energy from a single source to a subset of the scene's receiver patches. By using an efficient queue based scheduling system to process these subiterations, we show how radiosity solutions can be generated without the need for processor synchronization between iterations of the progressive refinement algorithm. The only significant source of interprocessor communication required by our method is for visibility calculations. We also describe a perceptually driven approach to visibility estimation, which employs an efficient volumetric grid structure and attempts to reduce the amount of interprocessor communication by approximating visibility queries between distant patches. Our algorithm also eliminates the need for dynamic load balancing until the end of the solution process and is shown to achieve a superlinear speedup in many situations View full abstract»

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  • Spectral volume rendering

    Publication Year: 2000 , Page(s): 196 - 207
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3580 KB)  

    Volume renderers for interactive analysis must be sufficiently versatile to render a broad range of volume images: unsegmented “raw” images as recorded by a 3D scanner, labeled segmented images, multimodality images, or any combination of these. The usual strategy is to assign to each voxel a three component RGB color and an opacity value α. This so-called RGBα approach offers the possibility of distinguishing volume objects by color. However, these colors are connected to the objects themselves, thereby bypassing the idea that in reality the color of an object is also determined by the light source and light detectors c.q. human eyes. The physically realistic approach presented, models light interacting with the materials inside a voxel causing spectral changes in the light. The radiated spectrum falls upon a set of RGB detectors. The spectral approach is investigated to see whether it could enhance the visualization of volume data and interactive tools. For that purpose, a material is split into an absorbing part (the medium) and a scattering part (small particles). The medium is considered to be either achromatic or chromatic, while the particles are considered to scatter the light achromatically, elastically, or inelastically. Inelastic scattering particles combined with an achromatic absorbing medium offer additional visual features: objects are made visible through the surface structure of a surrounding volume object and volume and surface structures can be made visible at the same time. With one or two materials the method is faster than the RGBα approach, with three materials the performance is equal. The spectral approach can be considered as an extension of the RGBα approach with greater visual flexibility and a better balance between quality and speed View full abstract»

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  • Perturbation methods for interactive specular reflections

    Publication Year: 2000 , Page(s): 253 - 264
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1540 KB)  

    We describe an approach for interactively approximating specular reflections in arbitrary curved surfaces. The technique is applicable to any smooth implicitly defined reflecting surface that is equipped with a ray intersection procedure; it is also extremely efficient as it employs local perturbations to interpolate point samples analytically. After ray tracing a sparse set of reflection paths with respect to a given vantage point and static reflecting surfaces, the algorithm rapidly approximates reflections of arbitrary points in 3-space by expressing them as perturbations of nearby points with known reflections. The reflection of each new point is approximated to second-order accuracy by applying a closed-form perturbation formula to one or more nearby reflection paths. This formula is derived from the Taylor expansion of a reflection path and is based on first and second-order path derivatives. After preprocessing, the approach is fast enough to compute reflections of tessellated diffuse objects in arbitrary curved surfaces at interactive rates using standard graphics hardware. The resulting images are nearly indistinguishable from ray traced images that take several orders of magnitude longer to generate 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