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Now showing 1 - 6 of 6
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    Faster Phong Shading via Angular Interpolation
    (Blackwell Publishing Ltd and the Eurographics Association, 1989) Kuijk, AAM.; Blake, E.H.
    One of the most successful algorithms that brought realism to the world of 3D image generation is Phong shading. It is an algorithm for smooth shading meshes of planar polygons used to represent curved surfaces. The level of realism and depth perception that can be obtained by Phong shading is attractive for 3D CAD applications and related areas. However, per pixel computation costs which were too high and/or artifacts, introduced by some of the more efficient evaluation methods and apparent only when displaying moving objects, are major factors mat blocked the common usage of Phong shading in highly interactive applications.In this paper we present angular interpolation for Phong shading planar polygons. Angular interpolation was a method especially designed to meet requirements as imposed by special purpose hardware we developed1, but turned out to be generally applicable. The angular interpolation method appears to be very efficient and reduces artifacts when displaying moving objects. Ideally a shading algorithm imposes no need for subdivision of patches as presented by the solid modelling system. Shading calculation via angular interpolation yields such an ideal algorithm. We will describe two alternative evaluation methods that trade off evaluation cost against level of accuracy. They both can handle light source and view point at arbitrary distances, but differ in level of accuracy. As a consequence these alternative evaluation methods do impose restrictions on the topology of patches and light sources. However, generally, the limitations imposed by these alternative shading methods are much more liberal than the limitations on patch size imposed by the geometry.The most economic evaluation method we present can incrementally compute the colour intensity along a scanline by two additions per pixel. The methods presented are generally applicable and can easily be implemented in hardware.
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    Experience with a Difference Engine for Graphics
    (The Eurographics Association, 1994) Kuijk, A.A.M.; Blake, E.H.; Steffens, E.H.; W. Strasser
    "The prototype of a novel raster graphics architecture has now become operational. The display hardware can be regarded as a very fast difference engine that works in two-dimensions. The speed is partly achieved by the use of custom VLSI components for the lowest level primitive operations and this permits the video rate reconstruction of images and other signals com pressed by encoding them on various polynomial bases. A novel feature of the architecture is that it avoids the use of a frame buffer. The paper describes our experience with the new hardware in terms of positive and negative performance aspects. We discuss the architecture and its operating parameters. Another part of the paper evaluates our ex perience of hardware development in an academic set ting. We believe there are significant lessons here for graphics researchers who might want to develop their own systems."
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    An Architecture for Interactive Raster Graphics
    (The Eurographics Association, 1992) Kuijk, A.A.M.; Blake, E.H.; Hagen, P.J.W. ten; P F Lister
    A radical reappraisal of the 3-D Interactive raster graphics pipeline has resulted In an experimentalarchitecture for a workstation which is currently being evaluated at the CWI. The principal features of thisarchitecture are that It:- concentrates exclusively on real-time interactive 3-D graphics (initially for CAD).- uses object space rather than Image space methods where possible.- avoids using a frame buffer.- only uses custom VLSI where commercial products are unlikely to suffice In the near term.Four years Into the proJect the system design Is complete and the major components have been acquired andthe custom VLSI chips hove been packaged and tested. The current experience with the system is based ondetailed simulations which gave a fairiy clear Idea on Its strengths and limitations. A complete, but reducedresolution, experimental prototype system is now being assembled."
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    The Mesh Propagation Algorithm for Isosurface Construction
    (Blackwell Science Ltd and the Eurographics Association, 1994) Howic, C.T.; Blake, E.H.
    A new algorithm, Mesh Propagation, is presented for the generation of isosurfaces from three-dimensional discrete data sets. While producing the same surface mesh as that generated by a corrected Marching Cubes algorithm, its characteristic is that it constructs an isosurface using connected strips of dynamically triangulated polygons. This compact data structure speeds up surface construction and reduces surface storage requirements. The surface can also be displayed more quickly, particularly where there is hardware support for rendering triangle strips.With engineering as well as medical imaging applications in mind, the algorithm can be used with both irregular and rectilinear grids of data, the primitive volume elements need not be hexahedral only, and volumes of heterogeneous polyhedral elements are supported without traversal complications.The algorithm propagates through the cells in the grid and uses the same lookup table topologies as Marching Cubes to determine patches of surface-element intersection- additional tables are used for non-hexahedral elements. The surface patches are dynamically coded into triangle strips which are then concatenated and linked to construct the surface. The data structures used for propagating through the volume overcome the topological ambiguities associated with table-based methods of surface construction and no holes are generated in the final mesh.
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    Report on the Third Eurographics Workshop on Graphics Hardware
    (Blackwell Publishing Ltd and the Eurographics Association, 1988) Blake, E.H.
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    XInPosse: Structural Simulation for Graphics Hardware
    (The Eurographics Association, 1991) Guravage, M.A.; Blake, E.H.; Kuijk, A.A.M.; A. Kaufman
    A structural simulator is used both to test hardware and to visualizesoftware that should run on that hardware. In a layered set of graphical hardwaresimulators, a structural simulator bridges the gap between hardware fidelity on theone side and sufficient performance to visualize graphics algorithms on the other. Essential design requirements were code extensibility and reusability. In order to achieve this, object-oriented methods were adopted. Important design criteria for graphical hardware simulators at this level are that both the exact digital state of the hardware and the graphical output be visualized interactively. The experience with using the XInPosse simulator is presented and analysed. XInPosse simulates a large systolicarray in custom VLSI for second order interpolation; in this case to produce shadedscanlines. XInPosse provides the user with a means of tracing commands within thearray while interactively setting breakpoints and displaying processors of particularinterest. It verified that the hardware could execute the graphics algorithms correctlyand that the limitations on numerical accuracy and range were graphically acceptable.An unexpected use was to facilitate communication between chip designers andthe graphics researchers. Problems in the documentation of the hardware and workarounds for hardware ""bugs"" were found more easily through the common reference frame provided by the simulator. It is the intention of the authors to use the modularity provided by the object-oriented design to produce a toolkit for building graphical hardware simulators."