Robust Epsilon Visibility

Florent Duguet 1 George Drettakis 1
1 REVES - Rendering and virtual environments with sound
CRISAM - Inria Sophia Antipolis - Méditerranée
Abstract : Analytic visibility algorithms, for example methods which compute a subdivided mesh to represent shadows, are notoriously unrobust and hard to use in practice. We present a new method based on a generalized definition of extremal stabbing lines, which are the extremities of shadow boundaries. We treat scenes containing multiple edges or vertices in degenerate configurations, (e.g., collinear or coplanar). We introduce a robust ε method to determine whether each generalized extremal stabbing line is blocked, or is touched by these scene elements, and thus added to the line's generators. We develop robust blocker predicates for polygons which are smaller than ε. For larger ε values, small shadow features merge and eventually disappear. We can thus robustly connect generalized extremal stabbing lines in degenerate scenes to form shadow boundaries. We show that our approach is consistent, and that shadow boundary connectivity is preserved when features merge. We have implemented our algorithm, and show that we can robustly compute analytic shadow boundaries to the precision of our chosen ε threshold for non-trivial models, containing numerous degeneracies.
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Communication dans un congrès
John Hughes. Proceedings of ACM SIGGRAPH, 2002, San Antonio, United States. ACM Press / ACM SIGGRAPH, pp.567 -- 575, 2002, Annual Conference Series. 〈10.1145/566654.566618〉
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Florent Duguet, George Drettakis. Robust Epsilon Visibility. John Hughes. Proceedings of ACM SIGGRAPH, 2002, San Antonio, United States. ACM Press / ACM SIGGRAPH, pp.567 -- 575, 2002, Annual Conference Series. 〈10.1145/566654.566618〉. 〈inria-00606723〉

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