does anybody know of an (efficient) algorithm to determine if a point

moving in discrete time has crossed a boundary in a multidimensional space?

The boundaries may be described by the union of several multidimensional

convex hulls.

I have seen algorithms for the two dimensional case, but it doesn't seem to

me that they extend easily to many dimensions.

pointers to articles (print, web or whatever), or source code (preferably

in matlab, but i'll take what i can get) would be very much appreciated.