[vtkusers] How to know a coordinate inside or outside a vtkPolyData?

[Simon]

Thankx, very Helpful.

vtkImplicitFunction specifies an abstract interface for implicit functions.
Implicit functions are real valued functions defined in 3D space, w =
F(x,y,z). Two primitive operations are required: the ability to evaluate the
function, and the function gradient at a given point. The implicit function
divides space into three regions: on the surface (F(x,y,z)=w), outside of
the surface (F(x,y,z)>c), and inside the surface (F(x,y,z)<c). (When c is
zero, positive values are outside, negative values are inside, and zero is
on the surface. Note also that the function gradient points from inside to
outside.)

Implicit functions are very powerful. It is possible to represent almost any
type of geometry with the level sets w = const, especially if you use
boolean combinations of implicit functions (see vtkImplicitBoolean).

vtkImplicitFunction provides a mechanism to transform the implicit
function(s) via a vtkAbstractTransform. This capability can be used to
translate, orient, scale, or warp implicit functions. For example, a sphere
implicit function can be transformed into an oriented ellipse.



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