[vtkusers] landscape Delaunay triangulation

[sebastien MARAUX]

Yes in that case I think Delaunay2D should be sufficient.
I first thought your data was regularly spaced, but it does
not seem to be the case, so you don't have a grid data,
but just "randomly" dispersed point set, isn't it ?

Then you actually need to use delaunay2D triangulation,
but computers have a big difficulty with computing more
than 1 or 2 millions points. Unfortunately I believe you
have around this number of input points?

For what you want to do, you should take a look
at triangle (but it is software, and not lib I believe) :

http://www-2.cs.cmu.edu/~quake/triangle.html
and its speed :
http://www-2.cs.cmu.edu/~quake/tripaper/triangle2.html

If any VTK user could have the time to adapt this methods to
Delaunay2D, it would be great !

Let me know if you do such job or turn triangle into
a library, it would interest me.

Hope this clarify things.

Sebastien MARAUX



----- Original Message -----
From: "Pedro Miranda" <Pedro.Miranda at edinfor.edp.pt>
To: <maraux at ondim.f>; <vtkusers at public.kitware.com>
Sent: Wednesday, December 18, 2002 5:31 PM
Subject: Re: [vtkusers] landscape Delaunay triangulation


>
>
> Hi Sebastian
> First let me thank you for your reply.
>
> As I told in my first message I'm new to VTK, but I also forgot to tell
> that I'm also new to CG.
> Let me explain better what I want to do so that you can tell me if
> delaunay2D is really what I need.
>
> I have some data from field capture representing landscape (terrain) in
> ascii format, plain xyz.
> What I need is to model the terrain to show as 3d landscape, actually I
> need to regenerate the terrain( or landscape) as a
> triangle mesh, so that I can save it as a directX file (.x).
>
> The best help I found in the web was Paul Bourke homepage
> (http://astronomy.swin.edu.au/~pbourke) and is Efficient Triangulation
> Algorithm Suitable for Terrain Modeling
> or  (http://astronomy.swin.edu.au/~pbourke/terrain/triangulate/).
> And after your reply I when to is source again and saw that he is actually
> doing 2d delaunay and not 3d as I taught.
>
>
> I've changed the source but it is still very slow when you have large
> amount of data.....like I have.
>
> I would apreciate any help or direction.
>
> Thanks a lot............
> Pedro.
>
>
>
>
>
>
> "sebastien MARAUX" <maraux at ondim.fr>@public.kitware.com on 12/18/2002
> 15:41:20
>
> Sent by:  vtkusers-admin at public.kitware.com
>
>
> To:   "Pedro Miranda" <Pedro.Miranda at edinfor.edp.pt>, "vtkusers"
>       <vtkusers at public.kitware.com>
> cc:
> Fax to:
> Subject:  Re: [vtkusers] landscape Delaunay triangulation
>
>
>
> Hello,
>
> It is a landscape, so height component is not to take
> into account for triangulation. A simple delaunay2D
> triangulation should do the trick if you only need
> a surface, as I would expect for a landscape.
> Delaunay3D will try to create a 3D object,
> which is not what you want, isn't it?
>
> And if you have numourous points, as I expect for a
> landscape, you would do better by triangulating your
> landscape "at hand", creating 2 arbitrary triangles for
> each square (just do a simple loop, add points to a
> vtkPoints when it is not done, and create 2 new
> VTK_TRIANGLE cells for each square from points ids),
> it will be far faster as number of points grow.
>
> If you think about decimating your mesh after, you may
> think about a delaunay insertion method right from
> the creation of your mesh.
>
> Seb
>
>
> ----- Original Message -----
> From: "Pedro Miranda" <Pedro.Miranda at edinfor.edp.pt>
> To: <vtkusers at public.kitware.com>
> Sent: Wednesday, December 18, 2002 4:07 PM
> Subject: [vtkusers] landscape Delaunay triangulation
>
>
> >
> > Hi,
> >
> > I've some landscape data in an ascii raw xyz format and you'd like to
> > reconstruct the terrain surface as a triangle mesh.
> >
> > Data example:
> >
> > -51685.689746;187747.836910;-0.100000;
> > -51687.829454;187747.825518;-0.100000;
> > -51688.772546;187746.820482;-0.100000;
> > -51684.526254;187746.843090;-0.100000;
> >
> > I've been researching Delaunay triangulation and Voronoi tessellation
and
> > found VTK (thank god I did) but being new to this library I'm still a
> > little lost among all the classes and potential of this library.
> >
> > Never the less I found that vtkDelaunay3D and/or
> > vtkSurfaceReconstructionFilter might the classes that I need to use to
> > accomplish that task.
> >
> > What I need is some guidelines from anyone who had experience in
> landscape
> > reconstruction from that kind of data using VTK.
> >
> > Thank you in advance.
> >
> > Pedro
> >
> > _______________________________________________
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