CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 04/29/2015 04:56 PM, Vinicius Azevedo wrote:
> I was confused by the cut/slice examples on the Polyhedron demo. I
> thought you was mentioning that, my bad. That's what I was looking for,
> thanks! I have some questions though on how to use this function:
>
>   * What should I pass to the function as starting halfedge? Is it an
>     edge returned by any_intersection?
I think so.

>   * Does this function add vertices from the polyline that is generated
>     from the intersection of the polyhedron with the plane? That's not
>     what I'm getting on my results
>     (https://dl.dropboxusercontent.com/u/5919734/bunnyCut1.png &&
>     https://dl.dropboxusercontent.com/u/5919734/bunnyCut2.png). It only
>     cuts the mesh by following pre-existent vertices. Also I'm having
>     the error "coplanar planes used for computing the intersection
>     plane, Return ORIGIN, Don't trust the result".
I never used the function. Could you share your code so that I can
give it a try?

Sebastien.

> Thanks for your help so far!
>
> Vinicius C. Azevedo.
>
> On Tue, Apr 28, 2015 at 10:24 AM, Sebastien Loriot (GeometryFactory)
> <
>  
> <mailto:>>
>  wrote:
>
>     On 04/28/2015 02:15 PM, Vinicius Azevedo wrote:
>
>         Hi Sebastian,
>
>         Thanks for your answer. I didn't expressed myself so well. What
>         I want
>         is to actually cut the mesh into two different independent parts
>         with a
>         given cut plane. In this video
>         https://www.youtube.com/watch?v=IOnk7PBv1AU and paper
>         http://www.math.ucla.edu/~jteran/papers/WJST14.pdf, they present
>         some
>         techniques to do that robustly. I saw the examples that you
>         mentioned,
>         and it seems that they only compute the intersections of planes and
>         Polyhedrons, but don't actually split it into different parts.
>
>
>     I believe this is what polyhedron_cut_plane_3.h is doing. The comment
>     for this function is:
>     // Cuts the polyhedron `poly' at plane `plane' starting at halfedge `h'.
>     // Traces the intersection curve of `plane' with `poly' starting at `h',
>     // cuts `poly' along that intersection curve and deletes the (connected)
>     // component on the negative side of the plane. The hole created along
>     // the intersection curve is filled with a new face containing the plane
>     // and the points in the vertices are computed.
>
>     Sebastien.
>
>
>         Vinicius C. Azevedo.
>
>         On Tue, Apr 28, 2015 at 1:48 AM, Sebastien Loriot (GeometryFactory)
>         
> <
>  
> <mailto:>
>         
> <mailto:
>  
> <mailto:>>>
>  wrote:
>
>              On 04/27/2015 04:31 PM, Vinicius Azevedo wrote:
>
>                  Hi all,
>
>                  I would like to know if anyone has a code snippet for
>                  slicing/splitting/cutting polyhedral meshes in two
>         different
>                  parts with
>                  arbitrary planes. I've seen some old threads about it
>
>         
> (http://cgal-discuss.949826.n4.nabble.com/Slices-in-a-mesh-td951695.html),
>                  but didn't find any code examples so far.
>
>                  Thanks!
>                  Vinicius C. Azevedo.
>
>
>
>              The thread you mention is to compute the intersection of a
>         polyhedron
>              with a plane which is one or several polygons. There is a
>         non documented
>              functor that is doing this in CGAL/Polyhedron_slicer_3.h
>              A better and documented version will be included in CGAL 4.8
>
>              In your case, it seems you want the intersection of a
>         polyhedron with
>              a halfspace.
>              There is another documented function
>         'CGAL::polyhedron_cut_plane_3'
>              I never used that is defined in CGAL/polyhedron_cut_plane_3.h
>              that should be doing what you want.
>
>              Sebastien.
>
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