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["Sebastien Loriot (GeometryFactory)" <>]

If you provide a complete minimal working example showing the
problem I can have a look at it.

S.


Max Harris wrote:
> OK, your suggestion worked for that case, but I want to write a function 
> that finds the correct Halfedge_handle for a given cutting plane. What 
> follows is my attempt, which doesn't work. What's wrong with it?
>
> Halfedge_handle FindUsableHandle(Polyhedron P, Plane pl)
> {
>     Halfedge_iterator hi;
>
>     for (hi = P.halfedges_begin(); hi != P.halfedges_end(); hi++) 
>     {
>         CGAL::Oriented_side test = pl.oriented_side(hi->vertex()->point());
>         if (test == CGAL::ON_POSITIVE_SIDE)
>         { 
>             cout << "point on positive side" << endl; 
>         }
>         else if (test == CGAL::ON_NEGATIVE_SIDE)
>         { 
>             cout << "point on negative side" << endl;
>             return hi;
>         }
>         else
>         { 
>             cout << "point over line" << endl; 
>         }
>     }
>
>     
>
>     return hi;
> }
>
>         Polyhedron result;
>         Halfedge_handle he = make_cube_3(result);
>
>         
>
>         CGAL::polyhedron_cut_plane_3(result, he->opposite()->next(), 
> pl3); // works
>         CGAL::polyhedron_cut_plane_3(result, FindUsableHandle(P, pl3), 
> pl3); // does not work. see output below 
>
> output: 
> **
> *Facet number: 0*
> *Plane: -0 -1 -0 -0*
> **
> *Normal: -0 -1 -0*
> **
> *Scaled normal: -0 0.1 -0*
> **
> *Transformed plane: -0 -1 -0 0.1*
> *point on positive side*
> *point on positive side*
> *point on positive side*
> *point on positive side*
> *point on positive side*
> *point on positive side*
> *point on negative side*
> *terminate called after throwing an instance of 
> 'CGAL::Postcondition_exception'*
> *  what():  CGAL ERROR: postcondition violation!*
> *Expr: D.is_valid(false,3)*
> *File: /usr/local/include/CGAL/halfedgeDS_cut_component.h*
> *Line: 126*
> *(gdb) *
>
>
> On May 27, 2011, at 2:29 AM, Sebastien Loriot (GeometryFactory) wrote:
>
> > Try with
> >
> > CGAL::polyhedron_cut_plane_3(result, he->opposite(), pl3);
> > instead of
> > CGAL::polyhedron_cut_plane_3(result, he, pl3);
> >
> > he->vertex() need to be on the negative side of the plane.
> >
> > S.
> >
> > Max Harris wrote:
> > > polyhedron_cut_plane_3() breaks when I try running the code below. 
> > > What am I doing wrong?
> > > Here's the output:
> > > *Plane: -0 -1 -0 -0*
> > > **
> > > *Normal: -0 -1 -0*
> > > **
> > > *Scaled normal: -0 0.1 -0*
> > > **
> > > *Transformed plane: -0 -1 -0 0.1*
> > > *terminate called after throwing an instance of 
> > > 'CGAL::Precondition_exception'*
> > > *  what():  CGAL ERROR: precondition violation!*
> > > *Expr: pred( h->vertex())*
> > > *File: /usr/local/include/CGAL/polyhedron_cut_plane_3.h*
> > > *Line: 120*
> > > Root::Root()
> > > {
> > >    Polyhedron P;
> > >    make_cube_3(P);
> > >    Facet_iterator f = P.facets_begin();        Plane pl2 = 
> > > f->plane(); // plane equation of the facet
> > >    cout << "Plane: " << pl2 << endl;
> > >        CGAL::Vector_3<Kernel> normal = pl2.orthogonal_vector();
> > >    cout << "\nNormal: " << normal << endl;
> > >        Vector sn = normal.transform(Transformation(CGAL::SCALING, -0.1));
> > >    cout << "\nScaled normal: " << sn << endl;
> > >        Plane pl3 = pl2.transform(Transformation(CGAL::TRANSLATION, sn));
> > >    cout << "\nTransformed plane: " << pl3 << endl;
> > >        Polyhedron result;
> > >    Halfedge_handle he = make_cube_3(result);
> > >        CGAL::polyhedron_cut_plane_3(result, he, pl3);
> > > }
> > > template <class Poly>
> > > typename Poly::Halfedge_handle Root::make_cube_3(Poly& P)
> > > {
> > >    // appends a cube of size [0,1]^3 to the polyhedron P.
> > >    CGAL_precondition( P.is_valid());
> > >    typedef typename Poly::Point_3         Point;
> > >    typedef typename Poly::Plane_3         Plane;
> > >    typedef typename Poly::Halfedge_handle Halfedge_handle;
> > >    Halfedge_handle h = P.make_tetrahedron(Point( 1, 0, 0),
> > >   Point( 0, 0, 1),
> > >   Point( 0, 0, 0),
> > >   Point( 0, 1, 0));
> > >    Halfedge_handle g = h->next()->opposite()->next();
> > >    P.split_edge( h->next());
> > >    P.split_edge( g->next());
> > >    P.split_edge( g);
> > >    h->next()->vertex()->point()     = Point( 1, 0, 1);
> > >    g->next()->vertex()->point()     = Point( 0, 1, 1);
> > >    g->opposite()->vertex()->point() = Point( 1, 1, 0);
> > >    Halfedge_handle f = P.split_facet( g->next(), 
> > > g->next()->next()->next());
> > >    Halfedge_handle e = P.split_edge( f);
> > >    e->vertex()->point() = Point( 1, 1, 1);
> > >    P.split_facet( e, f->next()->next());
> > >    CGAL_postcondition( P.is_valid());
> > >    g = h;
> > >    g->facet()->plane() = Plane( g->vertex()->point(),
> > > g->next()->vertex()->point(),
> > > g->next()->next()->vertex()->point());
> > >    g = h->opposite();
> > >    g->facet()->plane() = Plane( g->vertex()->point(),
> > > g->next()->vertex()->point(),
> > > g->next()->next()->vertex()->point());
> > >    g = h->next()->opposite();
> > >    g->facet()->plane() = Plane( g->vertex()->point(),
> > > g->next()->vertex()->point(),
> > > g->next()->next()->vertex()->point());
> > >    g = h->next()->next()->opposite();
> > >    g->facet()->plane() = Plane( g->vertex()->point(),
> > > g->next()->vertex()->point(),
> > > g->next()->next()->vertex()->point());
> > >    g = h->next()->next()->next()->opposite();
> > >    g->facet()->plane() = Plane( g->vertex()->point(),
> > > g->next()->vertex()->point(),
> > > g->next()->next()->vertex()->point());
> > >    g = g->next()->next()->opposite();
> > >    g->facet()->plane() = Plane( g->vertex()->point(),
> > > g->next()->vertex()->point(),
> > > g->next()->next()->vertex()->point());
> > >    return h;
> > > }
> > > On May 25, 2011, at 12:47 AM, Marc Glisse wrote:
> > > > On Wed, 25 May 2011, harris.max wrote:
> > > >
> > > > > I'm trying to get CGAL to generate a plane that's offset by some 
> > > > > specifiable
> > > > > distance from an existing plane, but everything I've tried so far isn't
> > > > > working. What's the best way to do this?
> > > >
> > > > What did you try that isn't working?
> > > >
> > > > There doesn't seem to be any function to do that directly, but you 
> > > > could for instance use Construct_orthogonal_vector_3 to get a normal 
> > > > vector, scale it to whatever distance you want, then translate the 
> > > > plane?
> > > >
> > > > --
> > > > Marc Glisse
> > > >
> > > > --
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> >
> >
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