Visibility and intersectin problems in plane geometry

We develop new data structures for solving various visibility and intersection problems about a simple polygon <italic>P</italic> on <italic>n</italic> vertices. Among our results are a simple <italic>&Ogr;</italic>(<italic>n</italic> log <italic>n</italic>) algorithm for computing the illuminated subpolygon of <italic>P</italic> from a luminous side, and an <italic>&Ogr;</italic>(log <italic>n</italic>) algorithm for determining which side of <italic>P</italic> is first hit by a bullet fired from a point in a certain direction. The latter method requires preprocessing on <italic>P</italic> which takes time <italic>&Ogr;</italic>(<italic>n</italic> log <italic>n</italic>) and space <italic>&Ogr;</italic>(<italic>n</italic>). Our main new tool in attacking these problems is geometric duality on the two-sided plane.

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