## Abstract

Given a terrain T and a point p on or above it, we wish to compute the region R_{p} that is visible from p. We present a generic radar-like algorithm for computing an approximation of R_{p}. The algorithm extrapolates the visible region between two consecutive rays (emanating from p) whenever the rays are close enough; that is, whenever the difference between the sets of visible segments along the cross sections in the directions specified by the rays is below some threshold. Thus the density of the sampling by rays is sensitive to the shape of the visible region. We suggest a specific way to measure the resemblance (difference) and to extrapolate the visible region between two consecutive rays. We also present an alternative algorithm, which uses circles of increasing radii centered at p instead of rays emanating from p. Both algorithms compute a representation of the (approximated) visible region that is especially suitable for visibility from p queries. Finally, we report on the experiments that we performed with these algorithms and with their corresponding fixed versions, using a natural error measure. Our main conclusion is that the radar-like algorithm is significantly better than the others.

Original language | English |
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Title of host publication | Proceedings of the Sixth Workshop on Algorithm Engineering and Experiments and the First Workshop on Analytic Algoritms and Combinatorics |

Editors | L. Arge, G.F. Italiano, R. Sedgewick |

Pages | 120-128 |

Number of pages | 9 |

State | Published - 22 Nov 2004 |

Event | Proceedings of the Sixth Workshop on Algorithm Engineering and Experiments and the First Workshop on Analytic Algorithms and Combinatorics - New Orleans, LA, United States Duration: 10 Jan 2004 → 10 Jan 2004 |

### Conference

Conference | Proceedings of the Sixth Workshop on Algorithm Engineering and Experiments and the First Workshop on Analytic Algorithms and Combinatorics |
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Country/Territory | United States |

City | New Orleans, LA |

Period | 10/01/04 → 10/01/04 |

## ASJC Scopus subject areas

- General Engineering