Robust polygon modelling

The paper provides a set of algorithms for performing set operations on polygonal regions in the plane using standard floating-point arithmetc. The algorithms are robust, guaranteeing both topological consistency and numerical accuracy. Each polygon edge is modelled as an implicit or explicit polygonal curve which stays within some distance fl of the original line segment. If the curve is implicit, fl is bounded by a small multiple of the rounding unit. If the curves are explicit, the bound on fl may grow with the number of curves. One can mix implicit and explicit representations to suit the application.