The concept of genericity is central to understanding intersections of geometric data structures in ePiX. For a working definition, two objects that are disjoint, tangent, or coincident intersect ``non-generically''. (Geometers will note that this differs substantially from the usual definition.) ePiX's intersection operators throw exceptions when the operands are non-generic. If a run of epix terminates with an error message, check that you are not trying to intersect badly-formed or situated objects.
In ePiX, a segment is extended into a line for purposes of
intersecting. Table 3.1 lists types of (generic!)
intersections in ePiX. Intersection is commutative, so only the top
half of the table is shown. Not all intersections are defined.