In visad/DelaunayCustom.java the method:
public static Irregular2DSet fill(Gridded2DSet set)
produces an Irregular2DSet for the interior of the boundary
defined by the argument 'Gridded2DSet set', which must have
manifold dimension = 1. If the ShapefileAdapter returns a
UnionSet of many Gridded2DSets, then you must extract the
one for the boundary of interest, or even combine multiple
Gridded2DSets into one for the entire boundary.