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[Sukhraj Singh <>]

Hello Sebastien,

I tried the following example to create a polyhedron from a segment in an incremental manner.
http://doc.cgal.org/latest/Polyhedron/Polyhedron_2polyhedron_prog_incr_builder_8cpp-example.html

I followed following procedure (In brief).
- Iterate the facets

If facet belongs to i-th segment.

Push its points to the incremental builder

Then add vertex to facet.

I got following error.
CGAL::Polyhedron_incremental_builder_3<HDS>::
lookup_halfedge(): input error: facet 1 shares a halfedge from vertex 1 to vertex 2 with facet 0.

I am getting the reason what is happening, but the sample provided "polyhedron_prog_incr_builder.cpp" is too simplistic.

Is there any other example where above case is handled. Because I think it can happen very often.

Any hint to resolve the above issue would be appreciated. 

Thanks

On Mon, May 23, 2016 at 8:38 PM, Sebastien Loriot (GeometryFactory) <> wrote:

If it does what you want, then yes.

Sebastien.

On 05/23/2016 04:57 PM, Sukhraj Singh wrote:

Okay,

Assuming I don't use connected_components().
And I directly create Polyhedrons from the segments, i.e.

- Iterate through polyhedron.
- Create polyhedron of a segment using Polyhedron_incremental_builder_3.

Is this correct way to do ? Or there is some better approach in CGAL.




On Mon, May 23, 2016 at 1:18 PM, Sebastien Loriot (GeometryFactory)

< <mailto:>> wrote:

    What I mean is if you need both clusters and segments but want to
    save on computation time, you can run the segmentation algorithm to
    extract
    segments and then clusters using `connected_components()` (instead of
    another run of segmentation).

    Sebastien.

    On 05/22/2016 02:32 PM, Sukhraj Singh wrote:

        Thanks for your answer, Sebastien
        Do I really need to use connected_components()

        I already have the "segment_pmap", where the value is the
        segment id to
        which that particular face belongs.
        And one could parse the Polyhedron and collect all the faces having
        particular segment ID.(Of-course I need to check, how to
        implement the same)
        Is my understanding correct ?



        Further, quoting from my previous email:

             Two spatially apart areas( i.e. not having
             common edges) of a Mesh may fall into same segment, since
        they had
             comparable SDF values.


        I am not sure about it, they of-course may fall into same
        cluster, but
        may not be to the same segment.  In such a case if, faces that don't
        share edge, will fall into different segment always, even though
        they
        were in same cluster, using connected_components() may not be
        required ?




        On Thu, May 12, 2016 at 6:00 PM, Sebastien Loriot (GeometryFactory)
        < <mailto:>

        <mailto: <mailto:>>> wrote:

             On 05/12/2016 02:16 PM, Sukhraj Singh wrote:

                 Salut,

                 The "Triangulated Surface Mesh Segmentation" module
        allows one to
                 segment a surface mesh using the SDF values.
                 It creates a Property Map which is colorized according
        to the
                 indices,
                 resulting into segments. Two spatially apart areas(
        i.e. not having
                 common edges) of a Mesh may fall into same segment,
        since they had
                 comparable SDF values.

                 My question is, how can one extract these segments.
        Since I want
                 to do
                 further processing on a segment separately. Also I
        would like
                 further
                 divide a segment, into say sub-segments , where a
        sub-segment
                 will have
                 faces which are not spatially apart, i.e.  a subset
        which is having
                 common edges only.



             Set the parameter output_cluster_ids to true when calling the
             segmentation function

        http://doc.cgal.org/latest/Surface_mesh_segmentation/group__PkgSurfaceSegmentation.html#ga8533ea7b1062ebbabe3bf23fed303f24

             If you need also the segments, then set the option to false and
             use the function connected_components() considering as
        constrained
             edges the edges between two faces belonging to different
             segments.

        http://doc.cgal.org/latest/Polygon_mesh_processing/group__keep__connected__components__grp.html#gabe2052b2281e1e628e68d8fea94be2d9


             Sebastien.



                 Thanks to inform.




                 P.S. I am a newbie.
                 --
                 Sukhraj Singh



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        Sukhraj Singh



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