Computing the connected components of simple rectilinear geometrical objects in d-space

Two or more geometrical objects (solids) are said to be connected whenever their union is a connected point set in the usual sense. Sets of geometrical objects are naturally divided into connected components, which are maximal connected subsets. We show that the connected components of a given collection of n horizontal and vertical line segments in the plane can be computed in O (n log n) time and O (n) space and prove that this is essentially optimal. The result is generalized to compute the connected components of a set of n rectilinearly-oriented rectangles in the plane with the same time and space bounds. Several extensions of the results to higher dimensions and to dynamic sets of objects are discussed.