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Now showing 1 - 10 of 482
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    Progressive Hulls for Intersection Applications
    (Blackwell Publishers, Inc and the Eurographics Association, 2003) Platis, Nikos; Theoharis, Theoharis
    Progressive meshes are an established tool for triangle mesh simplification. By suitably adapting the simplification process, progressive hulls can be generated which enclose the original mesh in gradually simpler, nested meshes. We couple progressive hulls with a selective refinement framework and use them in applications involving intersection queries on the mesh. We demonstrate that selectively refinable progressive hulls considerably speed up intersection queries by efficiently locating intersection points on the mesh. Concerning the progressive hull construction, we propose a new formula for assigning edge collapse priorities that significantly accelerates the simplification process, and enhance the existing algorithm with several conditions aimed at producing higher quality hulls. Using progressive hulls has the added advantage that they can be used instead of the enclosed object when a lower resolution of display can be tolerated, thus speeding up the rendering process.ACM CSS: I.3.3 Computer Graphics-Picture/Image Generation, I.3.5 Computer Graphics-Computational Geometry and Object Modeling, I.3.7 Computer Graphics-Three-Dimensional Graphics and Realism
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    Efficient Illumination by High Dynamic Range Images
    (The Eurographics Association, 2003) Kollig, Thomas; Keller, Alexander; Philip Dutre and Frank Suykens and Per H. Christensen and Daniel Cohen-Or
    We present an algorithm for determining quadrature rules for computing the direct illumination of predominantly diffuse objects by high dynamic range images. The new method precisely reproduces fine shadow detail, is much more efficient as compared to Monte Carlo integration, and does not require any manual intervention.
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    Gearbox Widget for Fine Adjustments by Hand Motion
    (The Eurographics Association, 2003) OSAWA, Noritaka; REN, Xiangshi; Andreas Kunz and Joachim Deisinger
    manipulation by hand is not suitable for making fine adjustments to virtual objects in an immersive environment because it is difficult to hold an unsupported hand in midair and then to release an object at a fixed point. Therefore we propose a virtual 3D gearbox widget. This gearbox widget enables the user to adjust a value precisely. A combination technique of this widget and hand manipulation can move virtual objects and place them in a target position quickly and precisely. For a comparison, we tested the usability of four techniques. Experiments showed that using the proposed gearbox in combination with direct manipulation was the best of the four techniques in terms of both performance data and subjective preference.
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    Ray Differentials and Multiresolution Geometry Caching for Distribution Ray Tracing in Complex Scenes
    (Blackwell Publishers, Inc and the Eurographics Association, 2003) Christensen, Per H.; Laur, David M.; Fong, Julian; Wooten, Wayne L.; Batali, Dana
    When rendering only directly visible objects, ray tracing a few levels of specular reflection from large, low-curvaturesurfaces, and ray tracing shadows from point-like light sources, the accessed geometry is coherentand a geometry cache performs well. But in many other cases, the accessed geometry is incoherent and a standardgeometry cache performs poorly: ray tracing of specular reflection from highly curved surfaces, tracing rays thatare many reflection levels deep, and distribution ray tracing for wide glossy reflection, global illumination, widesoft shadows, and ambient occlusion. Fortunately, less geometric accuracy is necessary in the incoherent cases.This observation can be formalized by looking at the ray differentials for different types of scattering: coherentrays have small differentials, while incoherent rays have large differentials. We utilize this observation to obtainefficient multiresolution caching of geometry and textures (including displacement maps) for classic and distributionray tracing in complex scenes. We use an existing multiresolution caching scheme (originally developed forscanline rendering) for textures and displacement maps, and introduce a multiresolution geometry caching schemefor tessellated surfaces. The multiresolution geometry caching scheme makes it possible to efficiently render scenesthat, if fully tessellated, would use 100 times more memory than the geometry cache size.
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    Visual Hierarchical Dimension Reduction for Exploration of High Dimensional Datasets
    (The Eurographics Association, 2003) Yang, J.; Ward, M.O.; Rundensteiner, E.A.; Huang, S.; G.-P. Bonneau and S. Hahmann and C. D. Hansen
    Traditional visualization techniques for multidimensional data sets, such as parallel coordinates, glyphs, and scatterplot matrices, do not scale well to high numbers of dimensions. A common approach to solving this problem is dimensionality reduction. Existing dimensionality reduction techniques usually generate lower dimensional spaces that have little intuitive meaning to users and allow little user interaction. In this paper we propose a new approach to handling high dimensional data, named Visual Hierarchical Dimension Reduction (VHDR), that addresses these drawbacks. VHDR not only generates lower dimensional spaces that are meaningful to users, but also allows user interactions in most steps of the process. In VHDR, dimensions are grouped into a hierarchy, and lower dimensional spaces are constructed using clusters of the hierarchy. We have implemented the VHDR approach into XmdvTool, and extended several traditional multidimensional visualization methods to convey dimension cluster characteristics when visualizing the data set in lower dimensional spaces. Our case study of applying VHDR to a real data set supports our belief that this approach is effective in supporting the exploration of high dimensional data sets.
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    PHANToM Haptic Device Implemented in a Projection Screen Virtual Environment
    (The Eurographics Association, 2003) Fischer, A.; Vance, J. M.; Andreas Kunz and Joachim Deisinger
    This research combines the PHANToM 1.5 haptic device with a six-sided projection screen virtual environment in order to explore the benefits haptic devices bring to this type of immersive environment. The PHANToM is placed on a specially designed and constructed work stand which allows the device to be moved anywhere in the virtual environment. An algorithm has been developed which maps the size of the CAD model represented in the virtual environment, or the movement of the CAD model, to the working space of the PHANToM. Two applications are explored which illustrate using the PHANToM for different tasks: exploring a large NURBS surface and installing an aircraft rudder pedal assembly.
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    A vision-based head tracking system for fully immersive displays
    (The Eurographics Association, 2003) Hogue, A.; Robinson, M.; Jenkin, M. R.; Allison, R. S.; Andreas Kunz and Joachim Deisinger
    Six-sided fully immersive projective displays present complex and novel problems for tracking systems. Existing tracking technologies typically require tracking equipment that is placed in locations or at- tached to the user in a way that is suitable for typical displays of five or less walls but which would interfere with the immersive experience within a fully enclosed display. This paper presents a novel vision-based tracking technology for fully-immersive projective displays. The technology relies on the operator wearing a set of laser diodes arranged in a specific configuration and then visually tracking the projection of these lasers on the external walls of the display outside of the user's view. This approach places minimal hardware on the user and no visible tracking equipment is placed within the immersive environment. This paper describes the basic visual tracking system including the hardware and software infrastructure.
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    Frontiers in 3D Photography: Reflectance and Motion
    (The Eurographics Association, 2003) Seitz, Steve; Peter Hall and Philip Willis
    The last decade has seen great progress in 3D shape capture technology, both in terms of research ad- vances and successful commercial systems. So why don't most people own 3D cameras? Aside from such issues as expense and size, there remain fundamental technical problems that restrict the applicability of the current state of the art. One of these problems is modeling realistic materials. If you look around, you'll notice that most objects are shiny and have specular highlights. However, virtually all shape recovery methods perform poorly for such surfaces. For this reason, it is common to paint an object white before scanning with a laser scanner. This limitation seems unnecessary, given that the human visual system appears to have no such problem{in fact, highlights should give us more information for shape inference. Another major limitation is that the 3D capture process is currently slow and laborious. In particular, very few techniques exist that can capture moving scenes. Obtaining accurate and complete models of moving scenes is challenging, due to the limited measurements that can be obtained at each instant in time. In this talk, I will describe new work from my research group that seeks to address these two problems{ modeling shiny scenes and moving scenes from photographs. We have recently developed shape capture methods that produce laser-scanner-quality results but for scenes with general re ective properties, including shiny surfaces and even anisotropic materials like brushed fur. I will also describe motion- scanning techniques that yield dense shape reconstructions of moving scenes.
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    A Fast Rendering Method for Refractive and Reflective Caustics Due to Water Surfaces
    (Blackwell Publishers, Inc and the Eurographics Association, 2003) Iwasaki, Kei; Dobashi, Yoshinori; Nishita, Tomoyuki
    In order to synthesize realistic images of scenes that include water surfaces, the rendering of optical effectscaused by waves on the water surface, such as caustics and reflection, is necessary. However, rendering causticsis quite complex and time-consuming. In recent years, the performance of graphics hardware has made significantprogress. This fact encourages researchers to study the acceleration of realistic image synthesis. We present herea method for the fast rendering of refractive and reflective caustics due to water surfaces. In the proposed method,an object is expressed by a set of texture mapped slices. We calculate the intensities of the caustics on the objectby using the slices and store the intensities as textures. This makes it possible to render caustics at interactive rateby using graphics hardware. Moreover, we render objects that are reflected and refracted due to the water surfaceby using reflection/refraction mapping of these slices.Categories and Subject Descriptors (according to ACM CCS): I.3.1 [Computer Graphics]: Hardware Architecture I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism
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    Mobile Augmented Reality for Environmental Management (MARE)
    (Eurographics Association, 2003) Danado, Jose; Dias, Eduardo; Romao, Teresa; Correia, Nuno; Trabuco, Adelaide; Santos, Carlos; Araujo, David; Duarte, Pedro; Rebocho, Rui; Palmeiro, Jose; Serpa, Joao; Costa, Manuel; Camara, Antonio
    Access to real-time data while in field observations is often a requested issue in environmental management. Additionally, it is easier to see that information spatially distributed where it makes sense, leveraging users of the task of searching for the context where the retrieved information can be applied. Augmented Reality (AR) is a technology that allows the superimposition of synthetic images over real images, providing augmented knowledge about the environment in the users vicinity. AR will also make the task more pleasant and effective for the user, since the required information is spatially superimposed over real information related to it. This short paper describes ANTS (Augmented Environments), an AR project for environmental management providing geo-referenced information to the user. The systems architecture has a flexible design based on a client/ server model, where several independent, but functionally interdependent modules are articulated. Therefore, modules can be moved from the server side to the client side or vice-versa, according to the client processing capacity. The system is being deployed in laptop computers and work is in progress to deploy the system using Personal Digital Assistant (PDA) devices. A 3D model and a geo-referenced database are used in the server for user positioning, and presentation components are used in the client to superimpose synthetic information over real images. Several applications for the system are being developed and will also be discussed in this short paper.