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Re: [cgal-discuss] CGAL newbie question


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  • From: Philipp Moeller <>
  • To:
  • Subject: Re: [cgal-discuss] CGAL newbie question
  • Date: Mon, 10 Sep 2012 14:53:10 +0200
  • Organization: GeometryFactory

Manu Kaul
<>
writes:

> Last question, is there a CGAL sample code repository, which shows examples
> for some common
> tasks? Or do I have to get those from the code snippets in the
> documentation?

You will need to get them from the documentation or from a CGAL tarball
which comes with a example directory where you can find all examples
sorted by package.

> On Mon, Sep 10, 2012 at 10:45 AM, Monique Teillaud <
> >
> wrote:
>
>> Le 10/09/12 10:29, Manu Kaul a écrit :
>>
>> Thanks Monique and Olivier. Will look into the tutorials. Its just that
>>> I haven't done much generic programming either, so wondering what the
>>> learning curve will be in that case.
>>>
>>
>> There is a learning curve, but I don't think that the "generic
>> programming" aspect itself is adding major difficulties (and it is a good
>> opportunity to learn more about it).
>> The difficulty is proportional to the needs. If you do easy things that
>> are already on the shelf, then it is easy. The examples should help a lot.
>> If you need precisely tailored complex stuff, things are getting harder.
>> That's fair...
>> Have fun.
>>
>> On Mon, Sep 10, 2012 at 10:26 AM, Olivier Devillers
>>> <
>>>
>>> <<>>>
>>> wrote:
>>>
>>> Le 9/9/12 8:18 AM, Manu Kaul a écrit :
>>>
>>> Hi all,
>>> I used the "Triangle" library from
>>>
>>> http://www.cs.cmu.edu/~quake/_**_triangle.html<http://www.cs.cmu.edu/%7Equake/__triangle.html>
>>>
>>> <http://www.cs.cmu.edu/%**7Equake/triangle.html<http://www.cs.cmu.edu/%7Equake/triangle.html>
>>> >
>>> <http://www.cs.cmu.edu/%__**7Equake/triangle.html
>>>
>>>
>>> <http://www.cs.cmu.edu/%**7Equake/triangle.html<http://www.cs.cmu.edu/%7Equake/triangle.html>>>
>>> by Jonathan
>>> Shewchuck to generate a Delaunay triangulation
>>>
>>> of my raw x,y,z points. I am trying to create an indexing
>>> structure and some distance bounds that make the shortest path
>>> calculation on a
>>> terrain faster + some other queries like range queries, and
>>> k-nearest neighbour queries as well.
>>>
>>> I noticed that in order to do some of these things I might need
>>> CGAL, but I understand that the learning curve can be quite steep.
>>> The things I need to do are :
>>> 1. Generate TINs at multiple levels of details by introducing
>>> Steiner points.
>>> 2. Being able to access the triangles and its adjacent triangles
>>> in raw form (like 0 1 2 vertices of triangle in
>>> counter-clockwise format)
>>> so that I can feed it to a "Chen and Han" shortest path
>>> implementation by O'Rourke
>>>
>>> (http://cs.smith.edu/~orourke/**__ShortestPaths/<http://cs.smith.edu/%7Eorourke/__ShortestPaths/>
>>>
>>> <http://cs.smith.edu/%**7Eorourke/ShortestPaths/<http://cs.smith.edu/%7Eorourke/ShortestPaths/>
>>> >
>>> <http://cs.smith.edu/%__**7Eorourke/ShortestPaths/
>>>
>>>
>>> <http://cs.smith.edu/%**7Eorourke/ShortestPaths/<http://cs.smith.edu/%7Eorourke/ShortestPaths/>
>>> >>)
>>>
>>> 3. Have the ability to compute the slope of each triangle and
>>> also all its interior angles.
>>> 4. Need to be able to *project* onto the terrain the 3D
>>> euclidean line between any two points of the terrain.
>>> 5. Generate a Voronoi diagram from the Delaunay (Triangle
>>> generates this too)
>>>
>>> 2 Triangulation of a terrain is what you need:
>>> http://www.cgal.org/Manual/__**beta/doc_html/cgal_manual/__**
>>> Triangulation_2/Chapter_main._**_html#Subsection_37.5.2<http://www.cgal.org/Manual/__beta/doc_html/cgal_manual/__Triangulation_2/Chapter_main.__html#Subsection_37.5.2>
>>>
>>> <http://www.cgal.org/Manual/**beta/doc_html/cgal_manual/**
>>> Triangulation_2/Chapter_main.**html#Subsection_37.5.2<http://www.cgal.org/Manual/beta/doc_html/cgal_manual/Triangulation_2/Chapter_main.html#Subsection_37.5.2>
>>> >
>>>
>>> 4 The triangles intersected by the vertical projection of a line on
>>> the terrain are given by
>>> http://www.cgal.org/Manual/__**beta/doc_html/cgal_manual/__**
>>> Triangulation_2_ref/Class___**Triangulation_2.html#Nested___**
>>> type_Line_face_circulator<http://www.cgal.org/Manual/__beta/doc_html/cgal_manual/__Triangulation_2_ref/Class___Triangulation_2.html#Nested___type_Line_face_circulator>
>>>
>>> <http://www.cgal.org/Manual/**beta/doc_html/cgal_manual/**
>>> Triangulation_2_ref/Class_**Triangulation_2.html#Nested_**
>>> type_Line_face_circulator<http://www.cgal.org/Manual/beta/doc_html/cgal_manual/Triangulation_2_ref/Class_Triangulation_2.html#Nested_type_Line_face_circulator>
>>> >
>>>
>>> 5 use "dual" fonctions of vertices and faces
>>>
>>> 3 are just basic computations
>>>
>>> 1 you have to manage levels of details yourself. CGAL triangulation
>>> supports insertion and deletions.
>>>
>>>
>>> --
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>>>
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>>>
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