CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

The difference you observe comes from the infimaximal box [1].
This means that you have another cube around your cube, which explains
why all numbers but #volumes are doubled.

Sebastien.

[1] http://doc.cgal.org/latest/Nef_3/index.html#title2


On 01/24/2017 08:28 PM, Nicholas Mario Wardhana wrote:
> Hello,
>
> I am creating a cube as a nef polyhedron by defining it as the
> intersections of the negative sides of the 6 bounding planes, based on
> the following example:
> http://doc.cgal.org/latest/Nef_3/index.html#title6
> It then checks the properties, saves the cube to a nef3 file, loads it
> again, and checks the property again
>
> I would expect that the cube has the following properties.
>
>   * 2-manifold (is_simple() == true)
>   * The number of volumes = 2 (inside and outside the cube)
>   * The number of shells = 2 (the inside and outside boundaries)
>   * The number of facets = 6
>   * The number of half-facets = 12
>   * The number of edges = 12
>   * The number of half-edges = 24
>   * The number of vertices = 8
>
> My code prints the followings.
>
>     CreateACube()
>     nefCube.is_simple() == true
>     nefCube.number_of_volumes(), expected 2, result = 3
>     GetNumberOfShells(nefCube), expected 2, result = 4
>     nefCube.number_of_facets(), expected 6, result = 12
>     nefCube.number_of_halffacets(), expected 12, result = 24
>     nefCube.number_of_edges(), expected 12, result = 24
>     nefCube.number_of_halfedges(), expected 24, result = 48
>     nefCube.number_of_vertices(), expected 8, result = 16
>
>
>
>     LoadACube()
>     nefCube.is_simple() == true
>     nefCube.number_of_volumes(), expected 2, result = 3
>     GetNumberOfShells(nefCube), expected 2, result = 4
>     nefCube.number_of_facets(), expected 6, result = 12
>     nefCube.number_of_halffacets(), expected 12, result = 24
>     nefCube.number_of_edges(), expected 12, result = 24
>     nefCube.number_of_halfedges(), expected 24, result = 48
>     nefCube.number_of_vertices(), expected 8, result = 16
>
>
> I did not get many of the expected properties.
>
> However, the nef3 file does state:
>
>     vertices   8
>     halfedges  24
>     facets     12
>     volumes    2
>     shalfedges 48
>     shalfloops 0
>     sfaces     16
>
>
> and when I cross-checked the result by loading the nef3 file to the
> polyhedron_3 demo (http://www.cgal.org/demo/4.9/polyhedron_3.zip), it
> correctly prints the followings.
>
>     Test_ByEquation (mode: flat+edges, color: #6464ff)
>     Nef_3 polyhedron
>
>     Number of vertices: 8
>     Number of edges: 12
>     Number of facets: 6
>     number of volumes: 2
>
>     Bounding box: min (0,0,0), max (2,2,2)
>
>     File:<path omitted>/CGAL/output/Test_ByEquation.nef3
>
>
> The minimum working code and the resulting nef3 file are attached. Could
> anyone please point out my mistakes? Thank you.
>
> Best regards,
> Nicholas Mario Wardhana