CGAL users discussion list

[Nicholas Mario Wardhana <>]

On 9 March 2012 17:33, Helmi Ben Hmida
<>
 wrote:
> Hello again,
> Thanks for your reactions to my mail. I ll try to put u in the big picture.
> Theses off files are generated from a VRML file containing the set of
> elements composing a scene.
> I´´m creating a small parser taking a vrml file as input and generating a
> set of off files as output correspondinf to the differents geometries
> existing inside.
> Unfortuantely, there arealso  duplicates points, but is it here the problem,
> since even the corrected OFF resent to me does not correspond to a
> Polydehron.
>
> PS: The form is not always a cube, but i´m sure it´s a closed one.
> PS: Please find one element from the vrml file (if u d like all the vrml
> file, i can provide it to you)
> Best
>
> Thanks in adavance
>
>  DEF Oid806_IfcWall_Wand__Mauerziegel_d_17_5_cm__i
>  Shape
>  {
>   appearance Appearance
>   {
>    material Material
>    {
>     diffuseColor 0.8 0.8 0.8
>    } # Material
>   } # Appearance
>   geometry IndexedFaceSet
>   {
>    ccw    TRUE
>    convex TRUE
>    solid  TRUE
>    coordIndex
>    [
>     0 1 2 3 -1,
>     4 5 6 7 -1,
>     8 9 10 11 -1,
>     12 13 14 15 -1,
>     16 17 18 19 -1,
>     20 21 22 23 -1
>    ] # coordIndex
>    coord Coordinate
>    {
>     point
>     [
>      19.454456 9.214429 9.195417,
>      19.454456 9.214429 6,
>      19.629456 9.214429 6,
>      19.629456 9.214429 9.195417,
>      19.629456 9.214429 9.195417,
>      19.629456 9.214429 6,
>      19.629456 13.049429 6,
>      19.629456 13.049429 8.724564,
>      19.629456 13.049429 8.724564,
>      19.629456 13.049429 6,
>      19.454456 13.049429 6,
>      19.454456 13.049429 8.724564,
>      19.454456 13.049429 8.724564,
>      19.454456 13.049429 6,
>      19.454456 9.214429 6,
>      19.454456 9.214429 9.195417,
>      19.454456 9.214429 6,
>      19.454456 13.049429 6,
>      19.629456 13.049429 6,
>      19.629456 9.214429 6,
>      19.629456 9.214429 9.195417,
>      19.629456 13.049429 8.724564,
>      19.454456 13.049429 8.724564,
>      19.454456 9.214429 9.195417
>     ] # Point
>    } # Coordinate
>    normal Normal
>    {
>     vector
>     [
>      -0 -1 0,
>      -0 -1 0,
>      -0 -1 0,
>      -0 -1 0,
>      1 -0 -0,
>      1 -0 -0,
>      1 -0 -0,
>      1 -0 -0,
>      0 1 0,
>      0 1 0,
>      0 1 0,
>      0 1 0,
>      -1 0 0,
>      -1 0 0,
>      -1 0 0,
>      -1 0 0,
>      0 0 -1,
>      0 0 -1,
>      0 0 -1,
>      0 0 -1,
>      0 0.121862767485053 0.992546959040671,
>      0 0.121862767485053 0.992546959040671,
>      0 0.121862767485053 0.992546959040671,
>      0 0.121862767485053 0.992546959040671
>     ] # Vector
>    } # Normals
>   } # Geometry
>  } # Shape
>
>

Hi Helmi,

My apology that it seems like my previous e-mail was sent to your
private inbox, instead of to CGAL mailing list.

Unfortunately I am not familiar enough with VRML to comment on your
VRML script, but if I understand correctly, your "polyhedron" will be
nowhere near being closed. Indeed if you manufacture the object, it
will be closed, but topologically speaking, the existence of boundary
halfedges in the form of rectangles' bounding edges means that your
"polyhedron" is just disconnected open meshes. In other words, your
"polyhedron" is not a polyhedron.

BTW, have you tried Bertrand's OFF file? Although I suppose the second
line should have been "8 6 12" (without the double quotes).

Best regards,
Nicholas