CGAL users discussion list

["Hui DING" <>]

Thank you for your answer, Monique Teillaud! I will look at it.

Thank you for your answer, Manuel Caroli! And you were right, I was talking 
about chapiter 27, I dont know why I kept saying 22, maybe cause that's my 
lucky number, lol.
And
> >     2) From some basic exemple of chapiter 22, i saw that we get the
> >     triangulation information by using "/ostream/", but I dont
> >     understand what every value stands for. (the dimention, number of
> >     finite, non-combinatorial, the number of cells are clear, but the
> >     others i cant figure out, anyone can help?).
> btw. it would be helpful to be a little more precise. I assume you are 
> talking about example 27.6.1, right? I'm not sure having understood your 
> question in the right way. In this example the triangulation is written to 
> a file via a std::ofstream using the output operator << .
> This is described under section "I/O" in 
> http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Triangulation_3_ref/Class_Triangulation_3.html
- The output file shows like this (I understand the first 9 lines, but for 
the others, I dont know..):
3              - the dimension
6              - the number of finite vertices
0 1 0        - the non-combinatorial information about vertices (point, etc)
0 0 0
1 0 0
0 0 1
2 2 2
1 1 1
11            - the number of cells
5 1 3 6     - ?
1 2 3 4     - ?
2 0 3 4     - ?
2 1 0 4     - ?
1 3 2 0     - ?
0 1 3 5     - ?
6 1 3 4     - ?
0 5 3 4     - ?
0 1 5 4     - ?
5 1 6 4     - ?
5 6 3 4     - ?
6 10 9 5     - ?
2 6 3 4     - ?
7 1 3 4     - ?
8 2 1 4     - ?
2 3 5 1     - ?
0 7 8 4     - ?
1 10 9 0     - ?
10 2 8 5     - ?
9 7 3 5     - ?
6 10 8 0     - ?
6 7 9 0     - ?

> >     3) Could I easily put my 3D points data to Triangulation_3, and then
> >     use the ostream to output the triangulation information of this
> >     object? and is there any "Viewer" can read this information and show
> >     the object in 3D? Or do i need to write it myself what chapiter do i
> >     need to read?
> See the link above, it is suggested to use GeomView.

- I jumped over this GeomView part, when I read the manuel. thank you for 
reminding me. But is it possible I use the GeomView on Windows XP?

thanks again!
Hui

----- Original Message ----- 
From: <>
To: 
<>
Sent: Tuesday, May 06, 2008 10:08 AM
Subject: Re: [cgal-discuss] Triangulation 3D (I'm SORRY that I forgot to 
change the subject)


> Manuel Caroli wrote:
> > Hello Hui Ding,
>
> > >     4) Once I construct the triangulation of my object 3D, I need the
> > >     normal of every facet of every cell, is there already some functions
> > >     who do that? or i need to calculate myself? how?
> >
> > I'm currently not aware of any such function.
>
> Hi
> you can get the points corresponding to the vertices of facet (see manual 
> of Triangulation_3 for the orientation of the facet) then use 
> CGAL::orthogonal_vector (see Kernel manual)
>
> best
> Monique Teillaud

----- Original Message ----- 
From: "Manuel Caroli" <>
To: 
<>
Sent: Monday, May 05, 2008 7:20 PM
Subject: Re: [cgal-discuss] Triangulation 3D (I'm SORRY that I forgot to 
change the subject)


> Hello Hui Ding,
>
> >     I have some data files that contain the values 3D points of the
> >     object 3D, and I'd like to use CGAL to represent the object. I just
> >     looked into the chapter22 of manuel, and i have some questions about
> >     both concept of science and use of library, I will appreciate it, if
> >     someone gives some helps:
> I hope you are talking about chapter 27.
> >      1) I can see that a vertex has /0/-face, the edge has 1 face, and a
> >     facet has 2 faces, but I don't understand how a cell has 3 face? why
> >     not 4, if a cell is a 3 simplex(tetrahedron)?
> The numbers actually indicate the dimension.
> Thus a cell IS a 3-face, whereas a facet IS a 2-face, an edge a 1-face and 
> a vertex a 0-face.
>
> >     2) From some basic exemple of chapiter 22, i saw that we get the
> >     triangulation information by using "/ostream/", but I dont
> >     understand what every value stands for. (the dimention, number of
> >     finite, non-combinatorial, the number of cells are clear, but the
> >     others i cant figure out, anyone can help?).
> btw. it would be helpful to be a little more precise. I assume you are 
> talking about example 27.6.1, right? I'm not sure having understood your 
> question in the right way. In this example the triangulation is written to 
> a file via a std::ofstream using the output operator << .
> This is described under section "I/O" in 
> http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Triangulation_3_ref/Class_Triangulation_3.html
>
>
> >     3) Could I easily put my 3D points data to Triangulation_3, and then
> >     use the ostream to output the triangulation information of this
> >     object? and is there any "Viewer" can read this information and show
> >     the object in 3D? Or do i need to write it myself what chapiter do i
> >     need to read?
> See the link above, it is suggested to use GeomView.
>
> >     4) Once I construct the triangulation of my object 3D, I need the
> >     normal of every facet of every cell, is there already some functions
> >     who do that? or i need to calculate myself? how?
> I'm currently not aware of any such function.
> >     5) I read only chapter 22 for my work right now(cause someone told
> >     me so), but if anyone has some conseils to learn the 3D
> >     triangulations like some chapiters or some tuturials
> >     corresponding to 3D triangulation or something else, please tell me?
> You can have a look into the first introductory chapters about kernels and 
> number types... apart from that chapter 27 (and maybe 28) should be fine.
>
> Best
>
> Manuel
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