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Computer Graphics and Applications, 2000. Proceedings. The Eighth Pacific Conference on

Date 5-5 Oct. 2000

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Displaying Results 1 - 25 of 61
  • Proceedings the Eighth Pacific Conference on Computer Graphics and Applications

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    Freely Available from IEEE
  • Optimizing network 3D data transmissions for interactive applications

    Page(s): 419 - 420
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    3D object data transfer was optimized to accelerate interactive 3D scene design and virtual-space layout applications. In these applications, downloading many 3D objects reduces the interactivity of the clients. We used level-of-detail based loading sequences and timing control methods to interleave data downloading and interactions. Experiments showed that the maximum interval between interactions was up to 6.42 times shorter. View full abstract»

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  • Authors index

    Page(s): 461 - 462
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    Freely Available from IEEE
  • Compression of indoor video sequences using homography-based segmentation

    Page(s): 290 - 450
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    We present a new compression algorithm for video sequences of indoor scenes, or more generally, sequences containing mostly planar and near-planar surfaces. Our approach utilizes edge and optical flow information in order to segment selected keyframes into regions of general shape, such that the motion of each region is predicted well by a planar homography. With this kind of motion prediction, the errors between the predicted intermediate frames and the actual ones are very small, and can be compactly encoded. Our results demonstrate significant improvements in the accuracy of the compressed video sequences, compared to standard general purpose video compression View full abstract»

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  • Practical texture mapping on free-form surfaces

    Page(s): 97 - 440
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    Concerns the problem of mapping photographic images on to the surface of a 3D object whose geometric data are already known. Although the minimal view selection algorithm of K. Matsushita and T. Kaneko (1999) enables the selection of a minimal number of camera positions, it often results in untextured patches due to camera misalignment: a deviation of actual camera position from the specified position. This paper proposes two new practical algorithms (double and product viewing) to ensure that all the polygons are textured even if there are unavoidable human errors in camera alignment. The performance of the algorithms is evaluated by simulation experiments View full abstract»

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  • Interactive behavioural update of large flocks

    Page(s): 425 - 426
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    The availability of powerful and affordable 3D PC graphics boards has made the rendering of rich immersive environments possible at interactive speeds. The scene update rate and the appropriate behaviour of objects within the world are central to this immersive feeling. We explore new techniques for increasing the efficiency of the flocking algorithm, which has been used extensively to emulate the flocking behaviour of creatures found in nature. The main contribution of this paper is a new method for imposing a hierarchical structure on the flock so that each members nearby neighbours can be determined more efficiently. This allows for far larger flocks to be updated at interactive speeds on a PC View full abstract»

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  • Visibility in the presence of occluders with curved boundaries

    Page(s): 105 - 441
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    Accurate global visibility information has become essential in global illumination rendering. Combinatorial structures, such as the visibility complex, aspect graphs and the visibility skeleton, are the seeds of a new topic of research motivated by practical problems in computer graphics and global illumination rendering. This is now attracting interest from the computational geometry, combinatorics, CAD and robotics communities. The initial motivation has been to accurately represent shadow boundaries generated by occluding surfaces in the path of light from emitting surfaces (sources) to receiving surfaces (receivers). This article adds to the rich body of research in this field by presenting solutions to the problem of occluders with curved boundaries. This has profound implications in three main areas: (1) the generation, maintenance and search functions associated with the global visibility complex, (2) mesh generation, and (3) global illumination rendering. We present a new visibility complex based on the proposed visibility skeleton. The new visibility complex has been designed to handle not only polygonal elements but also surfaces with curved boundaries. We have found that, even in simple 3D scenes, the new visibility complex generates less polygons in the meshing phase and a more accurate global illumination View full abstract»

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  • Implementation of a graphics design framework on the Web

    Page(s): 421 - 422
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    We propose a client-server graphics design framework and implement a room design system using CORBA. We have integrated technologies used in distributed computation (Java and CORBA) and computer graphics (VRML). To support multiuser collaborative design, we propose a supplier-consumer communication approach and implement it using the event service in CORBA. Our system can be applied in electronic commerce to improve the existing systems by allowing customers to select furniture and to visualize the whole furnished room in 3D View full abstract»

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  • Using isosurface methods for visualizing the envelope of a swept trivariate solid

    Page(s): 272 - 280
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    We present a method for calculating the envelope surface of a parametric solid object swept along a path in three-dimensional space. The boundary surface of the solid is the combination of parametric surfaces and an implicit surface where the Jacobian of the defining function has a rank deficiency condition. Using this condition, we determine a set of square sub-Jacobian determinants that must all vanish simultaneously on the implicit surface. When the generator of the swept surface is a trivariate tensor-product B-spline solid and the path is a B-spline curve, we can give a robust algorithm to determine the implicit surface. This algorithm is based upon the “marching tetrahedra” method, which is adapted to work on 4-simplices. The envelope of the swept solid is given by the union of the parametric and implicit surfaces View full abstract»

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  • Efficient coding of non-triangular mesh connectivity

    Page(s): 235 - 242
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    Describes an efficient algorithm for coding the connectivity information of general polygon meshes. In contrast to most existing algorithms, which are suitable only for triangular meshes and pay a penalty for the treatment of non-triangular faces, this algorithm codes the connectivity information in a direct manner. Our treatment of the special case of triangular meshes is shown to be equivalent to the Edgebreaker algorithm. Using our methods, any triangle mesh may be coded in no more than two bits/triangle (approximately four bits/vertex), a quadrilateral mesh in no more than 3.5 bits/quad (approximately 3.5 bits/vertex), and the most common case of a quadrilateral mesh with few triangles in no more than four bits/polygon View full abstract»

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  • Acceleration of Monte Carlo path tracing in general environments

    Page(s): 71 - 439
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    The paper describes a two pass algorithm capable of computing solutions to the global illumination in general environments (diffuse or glossy surfaces, anisotropically scattering participating media) faster than previous methods, by combining the strengths of finite element and Monte Carlo methods. A quick coarse solution is first computed with a clustered directional hierarchical method. This intermediate solution is used by a Monte Carlo method to accelerate computation of a final accurate solution by importance sampling, by means of link probabilities and adaptive probability density functions. Results from a first implementation of the algorithm for diffuse surfaces are presented View full abstract»

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  • A method for modeling and rendering dunes with wind-ripples

    Page(s): 427 - 428
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    This paper proposes a method for modeling and rendering realistic desert scenes. A desert terrain includes sand dunes and wind ripples. We use two types of scale models to form them. We render the dunes with the wind-ripples by bump-mapping using LOD (levels of detail) View full abstract»

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  • Virtual spectrophotometric measurements for biologically and physically-based rendering

    Page(s): 398 - 399
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    The main topic of the paper is virtual spectrophotometers, virtual spectrophotometry and strategies for reducing the number of samples required to obtain asymptotically convergent measurements. A brief section on applications of virtual spectrophotometry is presented. This is followed by a careful formulation of virtual spectrophotometers. A virtual spectrophotometer, being a virtual device, is only described by its geometry View full abstract»

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  • Interactive manipulation planning for animated characters

    Page(s): 417 - 418
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    Presents a brief overview of an algorithm for interactively animating object grasping and manipulation tasks for human figures. The technique is designed to efficiently generate feasible single-arm manipulation motions given high-level task commands. For moving an object, the motions necessary for a human arm to reach and grasp the object, re-position it and return the arm to rest are generated automatically within a few seconds on average. The method synthesizes motion “on-the-fly” by directly searching the configuration space of the arm. Goal configurations for the arm are computed using an inverse kinematics algorithm that attempts to select a natural posture. A collision-free trajectory connecting the arm's initial configuration to the goal configuration is computed using a randomized path planner. A high-level description of the methods is given, along with results from some computed examples using a human character model View full abstract»

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  • Arbitrary precise orientation specification for layout of text

    Page(s): 80 - 86
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    A novel method for the layout of text strings over some given free-form parametric base curves is considered. Each letter of the string is represented by a collection of cubic and linear Bezier curves. The layout of the string over the free-form parametric curve is derived as a symbolic composition of the string geometry (i.e. a sequence of Bezier curves) and a free-form parametric surface S(u, v) with the parameters u, v between zero and one, and S(u, 0) given by the base curve. This method has proven to provide great flexibility and give high quality results in layout of text View full abstract»

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  • Proceedings Seventh International Conference on Parallel and Distributed Systems: Workshops

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    The following topics were dealt with: parallel and multi-computing; communication and protocol; object-oriented systems; network architecture; image processing; multimedia database and application; Internet application; simulation and scientific visualisation; modelling, animation and virtual reality; quality of service; network performance; security; VPN; mobile computing; parallel computing application; interactive applications; multiagent framework, platform and tools; flexible network; physical agents; parallel architectures; and parallel algorithms View full abstract»

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  • Efficient processing of large 3D meshes

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    Summary form only given, as follows. Due to their simplicity, triangle meshes are often used to represent geometric surfaces. Their main drawback is the large number of triangles that are required to represent a smooth surface. This problem has been addressed by a large number of mesh simplification algorithms which reduce the number of triangles and approximate the initial mesh. Hierarchical triangle mesh representations provide access to a triangle mesh at a desired resolution, without omitting any information. The article presents an infrastructure for discrete geometry processing, including algorithms for 3D reconstruction, curvature computation, reverse engineering, mesh reduction, interactive multiresolution modeling and progressive transmission of arbitrary unstructured triangle meshes View full abstract»

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  • The intersection of two ringed surfaces

    Page(s): 146 - 444
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    Presents an efficient and robust algorithm to compute the intersection curve of two ringed surfaces, each being the sweep ∪ uCu generated by a moving circle. Given two ringed surfaces ∪uC1u and ∪vC2v, we formulate the condition C 1u∩C2v≠Ø (i.e. that the intersection of the two circles C1u and C 2v is non-empty) as a bivariate equation λ(u,v)= 0 of relatively low degree. Except for some redundant solutions and degenerate cases, there is a rational map from each solution of λ(u,v)=0 to the intersection point C1u∩C2v. Thus, it is trivial to construct the intersection curve once we have computed the zero-set of λ(u,v)=0. We also analyze some exceptional cases and consider how to construct the corresponding intersection curves View full abstract»

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  • Simulating the aurora borealis

    Page(s): 2 - 432
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    We present an algorithm to simulate the aurora borealis, commonly known as the “northern lights”, a natural phenomenon of great visual beauty and considerable scientific interest. The algorithm is based on the current understanding of the physical origin of the aurora. This natural display is mainly caused by high-energy electrons originating in the Sun and entering the Earth's atmosphere in narrow regions centered on the magnetic poles. These electrons collide with atmospheric atoms which are excited to higher energy levels. The excited atoms emit rapidly varying visible light in a curtain-like volume as they return to lower energy levels thereby creating the aurora. By simulating these light emissions along with the spatial and temporal distribution of the entering electrons, we are able to render the major visual aspects of auroral displays. This approach also allows the representation of time-dependent features that characterize the dynamic nature of the aurorae. The applicability of this auroral model for artistic and research purposes is illustrated through comparisons of synthetic images with photographs of real auroral displays View full abstract»

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  • Rendering iridescent colors appearing on natural objects

    Page(s): 15 - 433
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    Iridescent colors appearing on natural objects, such as the feathers of a hummingbird, surfaces inside seashells, and shells of beetles, are beautiful and impressive. The cause of such iridescent colors is interference of light inside multilayer film structures covering the natural objects. The paper proposes a method for realistically rendering iridescent colors appearing on natural surfaces, taking into account interference of light inside multilayer structures. To render the iridescent colors, we have developed an illumination model for multilayer structures fluctuated through the use of a hypertexture. We also have improved the hypertexture to be able to represent fluctuated parametric curved surfaces. Several examples of iridescent colors on the surfaces of a seashell and a beetle demonstrate the usefulness of the proposed method View full abstract»

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  • Intuitive virtual grasping for non haptic environments

    Page(s): 373 - 457
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    This paper presents an approach for grasping virtual objects in virtual environments with a data glove. Our focus lies on developing new methods that allow sensible realistic grasping gestures which correspond to human grasping behavior. To meet the demands of industrial applications, users must be able to grasp an object in an intuitive way with one or two hands and, beyond that, manipulate grasped objects between their fingers. To avoid the use of expensive force or touch feedback hardware, but also to ensure a safe grip on virtual objects, several forms of visual feedback are provided. First, we describe the basic algorithm for grasping with one or two hands and finally, we present a method to precisely manipulate the grasped objects between the virtual fingers View full abstract»

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  • Interactive rendering method for displaying shafts of light

    Page(s): 31 - 435
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    Recently graphics hardware has increased in capability, and is, moreover, now available even on standard PCs. These advances have encouraged researchers to develop hardware-accelerated methods for rendering realistic images. One of the important elements in enhancing reality is the effect of atmospheric scattering. The scattering of light due to atmospheric particles has to be taken into account in order to display shafts of light produced by studio spotlights and headlights of automobiles, for example. The purpose of the paper is to develop a method for displaying shafts of light at interactive rates by making use of the graphics hardware. The method makes use of hardware-accelerated volume rendering techniques to display the shafts of light View full abstract»

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  • View-dependent continuous level-of-detail rendering of terrain model

    Page(s): 404 - 405
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    The level-of-detail modeling method is an effective approach for the interactive visualization of complex models. In this paper, we propose a hierarchical tree structure based on the fractal dimension to organize a 3D terrain mesh model and to realize view-dependent continuous level-of-detail rendering of terrain data with a restricted quadtree triangulation method. The total algorithm can be divided into two stages: pre-processing and rendering. In pre-processing, it builds an adaptive hierarchical structure by considering the flatness of the terrain surface evaluated by the fractal dimension. Then it can generate a triangular approximation mesh by dynamically determining preserved data points according to the view-related parameters and performing a restricted quadtree triangulation. Some experiments demonstrate that it is simple and efficient and can be used to support the interactive dynamic rendering of terrain models View full abstract»

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  • Modelling of smoke flow taking obstacles into account

    Page(s): 135 - 443
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    Recently, displaying natural phenomena such as smoke has become a topic of interest in computer graphics. The ability to simulate the complex shapes and motion of the smoke particles is not only important but is also a difficult problem to solve. In this paper, we propose a method of displaying swirling smoke, including the consideration of its passage round obstacles. By using the idea of metaballs, we can easily represent the 3D density distribution of smoke. We solve the physical equation of the flow, and represent the vortices by using the vorticity vector. Therefore, we can make a model of the smoke flow even if there are obstacles in its path View full abstract»

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  • Interactive simulation of surgical cuts

    Page(s): 116 - 442
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    Presents a framework for the interactive simulation of surgical cuts, such as those practiced in surgical treatment. Unlike most existing methods, our framework is based on tetrahedral volume meshes providing more topological flexibility. In order to keep the representation consistent, we apply adaptive subdivision schemes dynamically during the simulation. The detection of collisions between the surgical tool and the tissue is accomplished by using an axis-aligned bounding-box hierarchy which was adapted for deformable objects. For haptic rendering and feedback, we devised a mechanical scalpel model which accounts for the most important interaction forces between the scalpel and the tissue. The relaxation is computed using a localized, semi-implicit ODE (ordinary differential equation) solver. The achieved quality and performance of the presented framework is demonstrated using a human soft-tissue model View full abstract»

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