A qualitative and quantitative visibility analysis in urban scenes

In this paper we present a mathematical model of a generic urban scene, whi ch can be used to answer a variety of visibility questions. Aside from its theoretical merit, the mathematical model provides an important analysis to ol to optimize urban walkthrough algorithms. We formulate the probability f or a given object to be visible from a given viewcell as a function of dist ance from the viewcell. We address various issues related to the implementa tion of virtual walkthrough, such as storage requirements, optimal viewcell size and cell-to-cell coherency, from which we derive space-effective data structures. Quantitative simulations verify the validity of our analysis. We simulate visibility in scenes with randomly distributed (Poisson) object s as well in pseudo-random (jittered) scenes, and compare these simulation results with our mathematical model. (C) 1999 Elsevier Science Ltd. All rig hts: reserved.