CGAL users discussion list

[Manu Kaul <>]

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?

Thanks,
Manu

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

< <mailto:olivier.devillers@inria.fr>> 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>> 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/>>)

        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>

    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>

    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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The greater danger for most of us lies not in setting our aim too high
and falling short; but in setting our aim too low, and achieving our mark.
- Michelangelo

--
Monique Teillaud
INRIA Sophia Antipolis - Méditerranée
http://www.inria.fr/sophia/members/Monique.Teillaud/

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The greater danger for most of us lies not in setting our aim too high and falling short; but in setting our aim too low, and achieving our mark.
- Michelangelo