Flying over a polyhedral terrain

We consider the problem of computing shortest paths in three-dimensions in the presence of a single-obstacle polyhedral terrain, and present a new algorithm that for any p>=1, computes a ([email protected])-approximation to the L"p-shortest path above a polyhedral terrain in O([email protected]) time and O(nlogn) space, where n is the number of vertices of the terrain, and c=2^(^p^-^1^)^/^p. This leads to a FPTAS for the problem in L"1 metric, a ([email protected])-factor approximation algorithm in Euclidean space, and a 2-approximation algorithm in the general L"p metric.