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Now showing 1 - 9 of 9
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    The Priority Face Determination Tree for Hidden Surface Removal
    (Blackwell Publishers Ltd and the Eurographics Association, 1998) James, A.; Day, A. M.
    Many virtual environments are built from a set of polygons that form the basis of objects in the scene. Using priority-list algorithms, the sequence in which these polygons are drawn is dependent upon the location of an observer; the polygons must be ordered correctly before a realistic image can be displayed. It is necessary for a scene to be drawn correctly in real time from all locations before the observer can move interactively around the scene with complete freedom.The binary-space partitioning (BSP) tree developed by Fuchs, Kedem and Naylor in 1980 stores the view independent priority of a set of polygons which can be used to obtain the correct order for any given view-point. However, the number of polygons grows significantly due to the BSP splitting stage, increasing the number of nodes in the tree. This affects linearly the number of tests necessary to traverse the tree to obtain the priority of the set of polygons.The algorithm presented here is built using its associated BSP tree, but attempts to reduce the number of tests to, log4/3n, at the cost of a tree of size of O(N1.5log4/3n?1), where n is the initial number of polygons in the scene, and N the resulting number after BSP splitting. To achieve the increase in run-time efficiency, a height plane is used to restrict the view point of the observer to a fixed height, but the key to the efficiency of the algorithm is in the use of polygonal dependencies. In the scene; if we know our location relative to the front or back of a polygon, then our position relative to one-quarter of the remaining polygons, in the expected worst-case, can be determined.
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    Five-dimensional Adaptive Subdivision for Ray Tracing
    (Blackwell Science Ltd and the Eurographics Association, 1994) Simiakakis, G.; Day, A. M.
    This paper presents a directional subdivision method for speeding up ray tracing. This method is easy to use, because it automatically adapts the subdivision to the scene relieving the user from having to set parameters for the subdivision. It also attempts a balance between 5D and spatial subdivision in order to benefit from both methods. A memory saving scheme is introduced and experimental results are presented.
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    Recent Developments and Applications of Haptic Devices
    (Blackwell Publishers, Inc and the Eurographics Association, 2003) Laycock, S. D.; Day, A. M.
    Over recent years a variety of haptic feedback devices have been developed and are being used in a number of important applications. They range from joysticks used in the entertainment industry to specialised devices used in medical applications. This paper will describe the recent developments of these devices and show how they have been applied. It also examines how haptic feedback has been combined with visual display devices, such as virtual reality walls and workbenches, in order to improve the immersive experience.ACM CSS: H.5.2 Information Interfaces and Presentation-Haptic I/O; I.3.8 Computer Graphics-Applications; I.6 Simulation and Modelling-Applications
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    Compression of Large-Scale Terrain Data for Real-Time Visualization Using a Tiled Quad Tree
    (The Eurographics Association and Blackwell Publishing Ltd., 2004) Platings, M.; Day, A. M.
    The aim of the rapid world modeling project is to implement a system to visualize the topography of the entire world on consumer-level hardware. This presents a significant problem in terms of both storage requirements and rendering speed. This paper presents the a??Tiled Quad Treea??, a technique and format for the storage of digital terrain models, to work as part of an integrated system for the visualization of global terrain data. We show how this format efficiently stores and compresses elevation data, in a way that allows the data to be read very rapidly from hard disk or similar storage medium, to facilitate real-time rendering. The results of compressing several distinct data sets are presented.
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    Planar Convex Hull Algorithms in Theory and Practice
    (Blackwell Publishing Ltd and the Eurographics Association, 1988) Day, A. M.
    Sequential and parallel planar convex hull algorithms, their applications and some of the problems encountered on implementations are described. Details of Pascal implementations are given for three of the sequential algorithms: Graham s, Floyd-Eddy and the Approximation method. The programs are compared experimentally.
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    Image Registration in a Coarse Three-Dimensional Virtual Environment
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Laycock, R. G.; Day, A. M.
    In recent years, the availability of off-the-shelf geometric data for an urban environment has increased. During rendering, ground level images are mapped onto the facades of the buildings to improve the visual quality of the scene. This paper focuses on a technique that enables ground level images to be automatically integrated into an existing coarse three-dimensional environment. The approach utilises the planar nature of architectural scenes to enable the automatic extraction of a building facade from an image and its registration into the virtual environment.
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    Survey of Real-Time Rendering Techniques for Crowds
    (The Eurographics Association and Blackwell Publishing Ltd., 2005) Ryder, G.; Day, A. M.
    Real-time rendering of photo-realistic humans is considerably outside the scope of current consumer-level computer hardware. There are many techniques, which attempt to bridge the gap between what is desired and what is possible. This paper aims to give an overview of the techniques designed to alter the complexity of the model s geometry (level of detail), or replace it with a flat image (visual impostor) and to improve the lighting model (lighting and shadows). Recent years have shown a boom in the power and availability of consumer-level programmable graphics processors, thus techniques that make use of these features are coming to the forefront.
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    Erratum: Conflict Neutralization on Binary Space Partitioning
    (Blackwell Publishers Ltd and the Eurographics Association., 2001) James, A.; Day, A. M.
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    Haptic Device Control - Will it Fit Standardized Input Models?
    (Blackwell Publishers Ltd and the Eurographics Association, 2001) Arnold, D. B.; Day, A. M.; Jennings, V.; Courtenay, A.; Duce, D. A.
    Over recent years a wide variety of interaction devices involving haptic feedback have been brought to the market, but they vary widely in terms of input measures recorded. These range from one dimensional input on a haptic feedback steering wheel to a six degree of freedom position and orientation device and further, to assemblies of such devices. On the surface most of the variations can be accommodated logically with standardized input models combining existing logical input devices and haptic feedback processes as acknowledgement/echos. However it is very uncertain whether such a model can adequately model the system requirements for effective haptic feedback.In this paper we review the input models that have developed over the past 20 years and ask "Is it the end of the road for the conceptual model of input incorporated into the early graphics standards and elaborated over the years?" In addition, to highlight the problems of implementation with haptic interaction, we describe a typical application, the simulation of a collision with a virtual wall.