Given a simple polygon P in the plane, we present new algorithms and data structures for computing the weak visibility polygon from any query line segment in P . We build a data structure in O(n) time and O(n) space that can compute the visibility polygon for any query line segment s in O(k log n) time, where k is the size of the visibility polygon of s and n is the number of vertices of P . Al...

Unit square (grid) visibility graphs (USV and USGV, resp.) are described by axisparallel visibility between unit squares placed (on integer grid coordinates) in the plane. We investigate combinatorial properties of these graph classes and the hardness of variants of the recognition problem, i. e., the problem of representing USGV with fixed visibilities within small area and, for USV, the gener...

We analyze how to efficiently maintain and update the visibility polygons for a segment observer moving in a polygonal domain. The space and time requirements for preprocessing are O(n) and after preprocessing, visibility change events for weak and strong visibility can be handled in O(log |VP|) and O(log(|VP1| + |VP2|)) respectively, or O(log n) in which |VP| is the size of the line segment’s ...

Limited visibility due to fog poses a significant danger to travelers. Accurate fog forecasts provide travelers with ample time to make preparations for low visibility conditions. Previous to this study, the Miami’s NWS Weather Forecast Office used a combination of factors to forecast fog, mainly moisture and wind speeds derived from forecast and observed soundings. However, a quantitative appr...

The coherence properties of a gas of bosonic atoms above the Bose-Einstein-condensation transition temperature were studied. Bragg diffraction was used to create two spatially separated wave packets, which interfere during expansion. Given sufficient expansion time, high fringe contrast could be observed in a cloud of arbitrary temperature. Fringe visibility greater than 90% was observed, which...

Given a simple polygon P with n vertices, the visibility polygon (VP) of a point q (VP(q)), or a segment pq (VP(pq)) inside P can be computed in linear time. We propose a linear time algorithm to extend VP of a viewer (point or segment), by converting some edges of P into mirrors, such that a given non-visible segment uw can also be seen from the viewer. Various definitions for the visibility o...

We show that the segment endpoint visibility graph of any finite set of 2n line segments contains a planar matching that does not use any segment edge, if the line segments in our set are convexly independent.