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Now showing 1 - 8 of 8
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    A Statistical Comparison of Two Hidden Surface Techniques: the Scan-line and Z-buffer Algorithms
    (Blackwell Science Ltd and the Eurographics Association, 1992) Slater, Mel; Drake, Kieron; Davison, Allan; Kordakis, Emmanouell and Billyard, Adam and Miranda, Eliot
    This paper compares two image space hidden surface removal algorithms for polygonal scenes. These are the z-buffer and scan-line algorithms. There is first an overview of each algorithm, followed by a simulation experiment, designed to compare the number of polygons per second which can be rendered by each algorithm. The simulation varies the number of polygons in the scene, and the size and distribution of polygons over the display. The results suggest that the z-buffer is preferred for a large enough number of polygons, however, smaller polygons and uniform distribution of polygons favour the scan-line approach. The analysis does not take into account the complexity of the shading rule, which is likely also to favour the scan-line method.
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    A Multiprocessor Implementation of Radiosity
    (Blackwell Science Ltd and the Eurographics Association, 1993) Ng, Adelene; Slater, Mel
    This paper describes a multi-processor implementation of form factor computation in the radiosity method. Form factors are computed using the ray casting method and the algorithm is enhanced with Binary Space Partition (BSP) Trees and bounding boxes. Experimental results are presented together with a discussion of load balance efficiency.
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    Liberation from Rectangles: A Tiling Method for Dynamic Modification of Objects on Raster Displays
    (Eurographics Association, 1988) Slater, Mel; Davison, Allan; Smith, Mark
    When graphics objects (also called segments) are used on raster display hardware, problems arise because of the mismatch between the high level requirements of object manipulation, and the low level representation from which the image is refreshed. This paper describes a tiling algorithm which provides a solution to the problems of damage repair and hit detection. In particular methods for handling object priority are discussed and experimental results showing the performance of the algorithm for a number of cases are presented.
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    A Top Down Method for Interactive Drawing
    (Blackwell Publishing Ltd and the Eurographics Association, 1988) Slater, Mel
    Traditional interactive drawing programs adopt a bottom-up approach, allowing the user to construct a picture by the use of discrete tools, for example, lines, circles, rectangles, and so on. This paper presents a different approach, which allows users to construct graphical objects by stretching and cutting existing objects. The representation is simply implemented, based on a ring of cubic Bezier curves, and use of the de Casteljau algorithm.
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    Liberation from Flatland: 3D Interaction Based on the Desktop Bat
    (Eurographics Association, 1991) Slater, Mel; Davison, Allan
    A novel device for 3D interaction is introduced, the Desktop Bat. This device is an evolutionary development of a mouse. It is like a mouse in that it is used on a desktop, but provides 5 degrees of freedom since in conjunction with translations it can be used to effect rotations about any combination of the principal axes. We discuss the requirements for 3D interaction which led to the design of the Desktop Bat, and the interaction models and software which allow it to be used as a 6 degrees of freedom input device.
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    Graphics Object Management in The X Window System
    (Blackwell Publishing Ltd and the Eurographics Association, 1990) Davison, Allan; Slater, Mel; Smith, Mark
    This paper describes a library for the creation and manipulation of geometrically defined graphical objects in The X Window System Objects are arranged in a 2.5D space, and can be transformed, made invisible or visible, or have their priority changed. Transformation of objects occurs immediately and with full damage repair, thus providing an essential requirement for the support of interactive graphics. The paper reports on an experimental implementation of the library and also discusses the implications of graphical objects in the X environment.
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    3D Interaction with the Desktop Bat
    (Blackwell Science Ltd and the Eurographics Association, 1995) Steed, Anthony; Slater, Mel
    Many applications now demand interaction with visualizations of 3D scenes and data sets. Current flat 2D displays are limited in their capacity to provide this not only by the display technology but the interaction metaphors and devices used. The Desktop Bat is a device that has 5 degrees of freedom whilst retaining the simplicity of use o fa mouse. To use it for general 3D interaction several metaphors were created for the tasks of navigation and cursor manipulation and a set of experiments were conducted to determine which metaphors were the most efficient in use. Of these metaphors, a velocity control metaphor was the best for navigation and a metaphor that applied rotations and translations relative to the eyepoint coordinate system was best for object control.
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    Dynamic Polygon Visibility Ordering for Head-Slaved Viewing in Virtual Environments
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Sadagic, Amela; Slater, Mel
    This paper presents an approach to visibility called the Viewpoint Movement Space (VpMS) algorithm which supports the concept of dynamic polygon visibility orderings for head-slaved viewing in virtual environments (VE). The central idea of the approach is that the visibility, in terms of back-to-front polygon visibility ordering, does not change dramatically as the viewpoint moves. Moreover, it is possible to construct a partition of the space into cells, where for each cell the ordering is invariant. As the viewpoint moves across a cell boundary typically only a small and predictable change is made to the visibility ordering. The cost to perform this operation represents a notable reduction when compared with the cost of resolving the visibility information from the BSP tree where the classification of the viewpoint with every node plane has to be performed. The paper demonstrates how the subdivision into such cells can represent the basic source for an acceleration of the rendering process. We also discuss how the same supportive data structure can be exploited to solve other tasks in the graphics pipeline.