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[Luis Rodriguez <>]

Here is an example of a 2D element from OFF file

OFF

4 4 0

1073.61 -213.673 13.15

1073.51 -213.513 13.15

1073.51 -213.673 13.15

1073.61 -213.513 13.15

3 3 0 2 

3 2 1 3 

3 1 2 0 

3 0 3 1 

Polyhedron P;

stream >> P;

Nef_polyhedron N (P);

/************************9 Intersection Model******************************/

//Here is where I get the problem 

On Wed, Jul 25, 2012 at 12:04 PM, Noel Warren <> wrote:

That's a slippery slope Luis.  You're confusing a few concepts.

In 2D we have

• Polygon_2
• Nef_polyhedron_2

In 3D we have

• Polyhedron_3
• Nef_polyhedron_3

From what I've seen in CGAL, surfaces are mentioned when speaking of Polyhedron_3.  When it comes to Nef_polyhedron_3, shells and volumes are the correct term, I believe.  Comments, Sebastien?

So, if I understand correcty you want to "extrude" a shape from 2D to 3D.  What are you working with and what do you want to get?  Polygon_2 -> Polyhedron_3 ?

2012/7/25 Luis Rodriguez <>

Noel, 

I am referring to solid as 3D objects, and surfaces as 2D.

Luis

On Wed, Jul 25, 2012 at 10:29 AM, Noel Warren <> wrote:

Sebastien, Is that always true?

  I know I'm getting lexical but... What if you have an OFF file with a cube that also has an extra face sticking out from it somewhere.  It is not manifold so you can't get from Polyhedron_3 to Nef_polyhedron_3.  At this point I would say it is not a solid.

  However, If you have a few Nef_polyhedron_3's  and you start performing operations on them, it is possible to get all sorts of stray geometry like faces, edges and points.  Even though they are not manifold you can still perform boolean operations on them.  This kind of makes me want to say they are solids.

  So, I guess my question is, "what's a solid?"

2012/7/25 Luis Rodriguez <>

Is there a way that I can make a solid out of the 2D Polyhedron?

Luis

On Wed, Jul 25, 2012 at 10:01 AM, Sebastien Loriot (GeometryFactory) <> wrote:

If there is no solid, there is only one volume which is the whole space.

Sebastien.

On 07/25/2012 09:45 AM, Luis Rodriguez wrote:

That's right and the outputs are garbage values, but I want to keep
those elements because they form part of a scene.

Luis

On Wed, Jul 25, 2012 at 9:14 AM, Sebastien Loriot (GeometryFactory)

< <mailto:>> wrote:

    I don't understand your question.
    If you don't have a "solid" some of the 9-intersection methods just
    don't make sense, do they?

    Sebastien.


    On 07/23/2012 03:47 PM, Luis Rodriguez wrote:

        Hi,

        I am working with 3D Nef_Polyhedrons, I am creating these
        nef_polyhedrons from Polyhedron from OFF files. The probles is
        that some
        of these Nef_Polyhedrons do not have volume and create some
        problems in
        my analysis of the 9-intersection method.

        My questions are, how can I convert or use Polyhedron_3 and
        Nef_Polyhedron_2? Or How can I add some volume to my
        Nef_Polyhedrons_3
        whithout changing my OFF file? or in any case how can I create
        Nef_Polyhedrons_3 from 8 Points_3?

        Any help would be useful, thank you.

        Sincerely,

        Luis Rodriguez



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