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["Tyver Ray" <>]

Thank you for your answer!

I'd like precisions your expert advice for the question below :
2) If my terrain has mountains and lakes, and I want to simplify the mesh. Lakes have the same altitude so
it isn't necessary to create a lot of triangle at these places.

To implement that I'm thinking about two solutions:

First method :
1. I triangulate with Delaunay with all my points in x, y, z from my file.
2. After I scan all the faces and check their neighbors' altitude 
If a lot of them have the same altitude I can remove some vertex.

Second method :
I filter the points before using the insert method

Wether first or second method I need all different level of details of my mesh...

Thanks in advance for your advice.

Tyv

2007/6/11, Andreas Fabri <>:

Hello,

A 3D triangulation is a tetrahedralization of space, and that's
not what you want.

A terrain is 2 1/2 D, and the triangulation works in the projection
on the xy-plane.

The order of insertion of points doesn't change the Delaunay
triangulation but might have an impact on speed.  Instead of
inserting them one by one, you better use the insert function
that takes an iterator range, and reorders them to get a
faster construction.

For using the mesh simplification on a triangulation class one
has to write the glue layer of the graph traits. This should
be rather straightforward, but it wasn't done yet.

andreas


wrote:
> Hello all members and experts !
>
> First of all I'd like to thank you for the wonderful work made in CGAL.
> I'm a new user and your API seem to be very powerfull! I've just started to discover 3D and I want to try your API right now!
>
> I watched to your docs, examples and posts but I'm not sure to have all understood...So please, I'd like a little help and orientation...
>
> I have a file with terrain points in x, y, z like notice below :
> X1 Y1 Z1
> .  .  .
> Xn Yn Zn
>
> I'd like to build a surface mesh to navigate in this terrain in 3D.
>
> 1) For that, I've seen the terrain.cpp file which seems to be interesting isn't ?
> But why does it use Delaunay_triangulation_2 and not a Delaunay_triangulation_3 ?
> The order of the points in the file are important, aren't they?
> In whitch order do I have to put my points?
>
> 2) If my terrain has mountains and lakes, and I want to simplify the mesh. Lakes have the same altitude so
> it isn't necessary to create a lot of triangle at these places.
> Does your triangulation automatically consider this ? If not, which example do that?
>
> 3) Another question is if I want to simplify my mesh. That is to say if I want to have less triangles
> on my mesh, can I use Triangulated Surface Mesh Simplification by Fernando Cacciola ? or is there a better code example?
>
> In advance, thank you a lot !
>
> Long life to CGAL! :)
>
> Tyv

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