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[houes <>]

Hello. I encountered 2D polygons that are not closed. These polygons are
formed by the intersection of a set of oriented lines. And I want to
construct Nef_polyhedron_2 to represent them. So I can use the new
representation to do union operations among open/closed polygons.

The problem I found with Nef_polyhedron_2 is that it only support *integer*
construction. 
What I want to do is define two lines, and define two Nef_Polygons using
these two lines, and do the intersection, just as in the sample
nef_2_intersection.cpp, but with *double number type*.
Suppose my lines are l1=(1.5, 2.4 , 3.1), l2=(-1.1, 2.3, 5.7). I have found
no way to represent them using Nef_polyhedron_2::Line, since in the example:

typedef CGAL::*Exact_integer *RT;
typedef CGAL::Filtered_extended_homogeneous<RT> Extended_kernel;
typedef CGAL::Nef_polyhedron_2<Extended_kernel> Nef_polyhedron;

only Exact_integer seems to work. I change this to CGAL::Gmpq,
CGAL::M_float, etc. all gives compiling error. 

So is it that Nef_polygon only work with integer number type?  Since all my
lines, planes using Epick kernel, I really want Nef_polygon to work with
double coordinates.

I also checked the sample code in Nef_3/handling_double_coordinates.cpp,
however it needs to first define a CGAL::Polyhedron_3<Epeck>. In my case,
the intersections of my planes are open, I cannot obtain a Polyhedron_3
first, so this does not solve my problem.

Hope some one could help me.
Thank you very much.



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