“…Finally, there is some work in GIS and virtual environment communities on finding paths that are occluded from a given set of observers [8,13,14,17]. All these papers sample a set of points on the terrain or polygonal environment, assign a weight to each point based on the visibility from a given set of observers, and use a steepest-descent, A* search, or Dijkstra's algorithm to compute a desired path.…”