This class is used to define a surface via a function f(x) -> R, where for a point y on the surface f(y) = 0. WARNING: This class is experimental and likely to change.
Signed distance function surface. If f0(p) = 0, the point p is possibly on the surface, which case ImplicitSurface::f1 can be called to check.
For a point for which f0 pprox 0, return <= is point is on is on the surface. Can be used for creating open surfaces by discarding with any artificial closure.
The membership flag