CGAL users discussion list

[thierry Fernandez <>]

i think you have to use boolean operations like in this example:

Nef_polyhedron N1(Plane_3( 1, 0, 0,-1));

Nef_polyhedron N2(Plane_3(-1, 0, 0,-1));

Nef_polyhedron N3(Plane_3( 0, 1, 0,-1));

Nef_polyhedron N4(Plane_3( 0,-1, 0,-1));

Nef_polyhedron N5(Plane_3( 0, 0, 1,-1));

Nef_polyhedron N6(Plane_3( 0, 0,-1,-1));

Nef_polyhedron I1(!N1 + !N2); // open slice in yz-plane

Nef_polyhedron I2(N3 - !N4); // closed slice in xz-plane

Nef_polyhedron I3(N5 ^ N6); // open slice in yz-plane

Nef_polyhedron Cube1(I2 * !I1);

Cube1 *= !I3;

Nef_polyhedron Cube2 = N1 * N2 * N3 * N4 * N5 * N6;

CGAL_assertion(Cube1 == Cube2); // both are closed cube

CGAL_assertion(Cube1 == Cube1.closure());

CGAL_assertion(Cube1 == Cube1.regularization());

CGAL_assertion((N1 - N1.boundary()) == N1.interior());

CGAL_assertion(I1.closure() == I1.complement().interior().complement());

CGAL_assertion(I1.regularization() == I1.interior().closure());

return 0

2015-06-12 16:23 GMT+02:00 Qingnan Zhou <>:

I have created a minimal example to illustrate this problem.  The code is really short and can be downloaded from

https://gist.github.com/qnzhou/03d5c2fde1032bf2a97e

Please let me know if you are not able to reproduce my result.  Any help would be appreciated.

best,

James

On Sat, Jun 6, 2015 at 11:50 AM, Qingnan Zhou <> wrote:

Dear all,

I noticed that CGAL's Nef Polyhedron gave incorrect result when the input contains multiple nested shells such as the nested_ball.off, which consists of 4 concentric spheres with normals pointing outward and inward in an alternating fashion.  When intersecting it with rectangular block, box.off, it produces the following output: out.off:

Where the correct output should be the following:

Is there anything special I need to do when using CGAL's Nef polyhedron class?  Thanks in advance!

best,

James