A "field of view" (FOV) consists of all possible directions along which scalar valued functions satisfy selected thresholds. This combination of a scalar function and a threshold is called a FOV constraint and a method is used to compute one or more directional contours or horizons that encompass regions of space that comprise FOV. The method is independent from the nature or the number of FOV constraints. If a single constraint produces multiple regions or regions with holes, the constraint is preferably redefined as a set of several simpler constituent constraints combined using logical AND operations. Each constituent constraint produces a single closed boundary contour with constraint region inside or outside of the contour.