Probing a scene of nonconvex polyhedra

We show, in this paper, how the exact shapes of a class of polyhedral scenes can be computed by means of a simple sensory device issuing probes. A scene in this class consists of disjoint polyhedra with no collinear edges, no coplanar faces, and such that no edge is contained in the supporting plane of a nonincident face. The basic step of our method is a strategy for probing a single simple polygon with no collinear edges. When each probe outcome consists of a contact point and the normal to the object at the point, we present a strategy that allows us to compute the exact shape of a simple polygon with no collinear edges by means of at most3n — 3 probes, wheren is the number of edges of the polygon. This is optimal in the worst case. This strategy can be extended to probe a family of disjoint polygons. It can also be applied in planar sections of a scene of polyhedra of the class above to find out, in turn, each edge of the scene. If the scene consists ofk polyhedra with altogethern faces andm edges, we show that probes are sufficient to compute the exact shapes of the polyhedra.This work has been supported in part by the ESPRIT Basic Research Action No. 3075 (ALCOM).