Analogously to the Hessian normal form of a line, the normal form
of a planar curve is defined. Thus any planar curve for which
the normal form exists can be considered as an implicit curve and all such
curves can be treated in a uniform way. Hence the simple implicit blending
methods are applicable. Offsets are just level curves of the oriented
distance function h. Bisectors of two curves have simple implicit
representations.
-blending of two Bézier curves