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    Correct Shading of Regularized CSG Solids Using a Depth-Interval Buffer

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    117-138.pdf (1.641Mb)
    Date
    1990
    Author
    Rossignac, Jaroslaw R.
    Wu, Jeffrey
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    Abstract
    A convenient interactive design environment requires efficient facilities for shading solid models represented in CSG. Shading techniques based on boundary eval­ uation or ray casting that require calculations of geometric intersections are too ineffi­ cient for interactive graphics when eSG primitives with curved (parametric) surfaces are involved. Projective approaches, where the primitive surfaces are scan-converted using standard hardware-supported graphic functions are preferred. Since not all the points of the faces of a CSG primitive lie on the CSG solid, scan conversion must be combined with a procedure that tests the produced 3D surface-points against the original CSG ex­ pression. Point classifications against primitives defined by arbitrary curved boundaries may be performed, without geometric intersections, through depth-comparisons at each pixel. This approach has been implemented for the Pixel-Power machine by researchers at UNC. It deals with complex CSG trees by converting CSG expressions into sum-of­ product form and repeatedly scan-converting the primitives of each product. The Trickle algorithm, which considerably reduces the number of scan-conversions in the general case has been developed at IBM Research and presented elsewhere. This paper discusses sev­ eral recent improvements to the original Trickle algorithm. The overall algorithm has been simplified. The scan-conversion process and the point classification tests have been modified to correctly handle cases where several primitive faces coincide within an arbi­ trary numerical resolution. These enhancements are not only necessary for on/on cases in regularized Boolean expressions, but also for processing pairs of faces near their common edges. Finally, we point out that a simple two-pass extension of the trickle algorithm using an auxiliary shadow buffer suffices to compute directly from CSG shaded images with shadows.
    BibTeX
    @inproceedings {10.2312:EGGH:EGGH90:117-138,
    booktitle = {Eurographics Workshop on Graphics Hardware},
    editor = {Richard Grimsdale and Arie Kaufman},
    title = {{Correct Shading of Regularized CSG Solids Using a Depth-Interval Buffer}},
    author = {Rossignac, Jaroslaw R. and Wu, Jeffrey},
    year = {1990},
    publisher = {The Eurographics Association},
    ISSN = {1727-3471},
    ISBN = {3-540-54291-4},
    DOI = {10.2312/EGGH/EGGH90/117-138}
    }
    URI
    http://dx.doi.org/10.2312/EGGH/EGGH90/117-138
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    Eurographics Association copyright © 2013 - 2023 
    Send Feedback | Contact - Imprint | Data Privacy Policy | Disable Google Analytics
    Theme by @mire NV
    System hosted at  Graz University of Technology.
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