3D envelopes

3D envelopes. In: Cgal User and Reference Manual: ... The Envelope-Traits Concept: The implementation of the envelope-computation algorithm is generic and can handle arbitrary surfaces. It is parameterized with a traits class, which defines the geometry of surfaces it handles, and supports all the necessary functionality on these surfaces, and on their projections onto the xy-plane. The traits class must model the EnvelopeTraits_3 concept, the details of which are given below.