Nef polygon

Nef polygons and Nef polyhedra are the sets of polygons (resp. polyhedra) which can be obtained from a finite set of halfplanes (halfspaces) by Boolean operations of set intersection and set complement. The objects are named after the Swiss mathematician Walter Nef (1919–), who introduced them in his 1978 book on polyhedra.[1][2]

Since other Boolean operations, such as union or difference, may be expressed via intersection and complement operations, the sets of Nef polygons (polyhedra) are closed with respect to these operations as well.[3]

In addition, the class of Nef polyhedra is closed with respect to the topological operations of taking closure, interior, exterior, and boundary. Boolean operations, such as difference or intersection, may produce non-regular sets. However the class of Nef polyhedra is also closed with respect to the operation of regularization. [4]

Convex polytopes are a special subclass of Nef polyhedra, being the set of polyhedra which are the intersections of a finite set of half-planes.[5]

References

  1. ^ Nef, W. 1978. Beiträge zur Theorie der Polyeder. Herbert Lang, Bern.
  2. ^ Bieri, H. "Nef polyhedra: A brief introduction". Computational Suppl. 1995, 10, 43–60.
  3. ^ "2D Boolean Operations on Nef Polygons", the CGAL package overview
  4. ^ AutoCAD Nef Polyhedron Implementation by Jeremy Tammik, 2007
  5. ^ Boolean Operations on 3D Selective Nef Complexes: Optimized Implementation and Experiments. Peter Hachenberger and Lutz Kettner. In: Proc. of 2005 ACM Symposium on Solid and Physical Modeling (SPM), Boston, MA. June, 2005.