CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

If you want to stick to Polyhedron_3, the original mechanism was using
the incremental builder:
http://doc.cgal.org/latest/Polyhedron/classCGAL_1_1Polyhedron__incremental__builder__3.html

If you can switch to Surface_mesh, then you have function available 
doing exactly what you want:
http://doc.cgal.org/latest/Surface_mesh/classCGAL_1_1Surface__mesh.html#ad2e8dedad669cb3637d6a7f8207caed5
http://doc.cgal.org/latest/Surface_mesh/classCGAL_1_1Surface__mesh.html#a47c2561d1430def60b9e538482ea2adb

If you want to write code that does not depend on the data structure,
you can use the BGL API:

put(get(CGAL::vertex_point, sm), add_vertex(sm), point_coordinates);

and use the helper function for creating a face:

http://doc.cgal.org/latest/BGL/group__PkgBGLEulerOperations.html#gada1dd2320a083dbfe09ddacafdaf8b19

Sebastien.

On 03/18/2017 08:10 PM, hossan.nazmul wrote:
> Dear CGAL mailing list,
>
> I am a CGAL beginner and have few problems using Polyhedron_3 class.
>
> Problem description:
> I have a LoD2 3D CityGML building that has to be decomposed and stored in a
> topological data structure such like Half edge data structure. I was
> searching for an example CGAL program that takes the Polygon (Vertices) as
> an input and is able to store it into Half edge data structure. The
> LinearRing is consists of points which represent actually a polygon:
>
> for an example: (my polygon looks like following)
> <gml:Polygon gml:id="GEOM_629113">
> <gml:exterior>
> <gml:LinearRing gml:id="GEOM_629113_0_">
> <gml:posList srsDimension="3">390839.695902067 5819139.47788488
> 33.8699989318848 390839.20858174 5819139.44457522 33.8699989318848
> 390838.722880716 5819139.49639365 33.8699989318848 390841.021950274
> 5819140.0657906 33.8699989318848 390840.616573399 5819139.79328419
> 33.8699989318848 </gml:posList>
> </gml:LinearRing>
> </gml:exterior>
> </gml:Polygon>
>
> Questions:
> Q1: How do I store these 3D points/vertices into a CGAL half edge data
> structure?
> Q2: How do I know from the data that which is the next half edge, previous
> half edge, incident vertex and etc
> Q3: I can make a triangle with three points and create a CGAL Polyhedron
> object. How can I combine all points and store into half edge data
> structure?
>
> I hope someone from this CGAL discussion group can help me to find the
> possible solution to my problem. It would be a great help if you can share
> some example code so that I can understand it easily.
>
> Thanks and regards,
> Nazmul
>
>
>
> --
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> http://cgal-discuss.949826.n4.nabble.com/Store-a-polygon-into-a-half-edge-data-structure-using-CGAL-Polyhedron-3-class-tp4662587.html
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