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Re: [cgal-discuss] Newbie question about CGAL Hierarchy Triangulation 3.


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  • From: Juliano Costa <>
  • To:
  • Subject: Re: [cgal-discuss] Newbie question about CGAL Hierarchy Triangulation 3.
  • Date: Fri, 7 Aug 2009 14:51:14 -0300
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Hello Manuel,
 
Some additional issues:
 
1. About Alpha Shapes:
- As you suggested I tried to do something nested in order to set my ->info() information along with the added vertices.
My used declaration is like this:
 
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
//My info is just a ordered index for the vertices
typedef CGAL::Triangulation_vertex_base_with_info_3<CPUInt64_t, K> Vbi;
typedef CGAL::Alpha_shape_vertex_base_3<K,Vbi> AsVbi;
typedef CGAL::Alpha_shape_cell_base_3<K> AsCb;
typedef CGAL::Alpha_shape_3<DelaunayTriangleHierarchy> Alpha_shape_3;
typedef Alpha_shape_3::Alpha_iterator Alpha_iterator;
typedef Alpha_shape_3::NT NT;
 
Then I got these errors:
error C2039: 'set_down' : is not a member of 'CGAL::Alpha_shape_vertex_base_3<Gt,Vb>'
error C2039: 'set_up' : is not a member of 'CGAL::Alpha_shape_vertex_base_3<Gt,Vb>'

Am I doing anything wrong about your suggestion?!
 
I didn't understang why if I use "incident_cells(infinite_vertex(), output_iterator)" I wouln't
need the index any longer.
 
I'm using this ->info to set the index, so after the triangulation the indexes of the vertices
are the same as when I add it, since after the insertion the initial order is not guaranteed,
right?! So I guess this info is fundamental. Or not???
 
2. About the Surface Reconstruction:
- The Surface Reconstruction seems to be great for any kind of points cloud but
I have a point cloud with x,y,z only (not the normals) and then I tried to use the
example  "..\examples\Point_set_processing_3\normal_estimation" to calculate
the necessary oriented normals for the Poisson reconstruction.
 
I'm trying to use it on a x,y,z file of a points cloud with 50000 points and the
program is freezing on the second fase (normals orientation). See the output
of the program:
 
tunnel_50mil.xyz tunnel_50mil_normals.xyz
Normal estimation
Open tunnel_50mil.xyz for reading...
Reads file tunnel_50mil.xyz: 50000 points, 2.496 seconds
Estimates Normals Direction by Jet Fitting (k=18)...
Calls jet_estimate_normals()
  6 Mb allocated
  Creates KD-tree
  11 Mb allocated
  Computes normals
  14 Mb allocated
End of jet_estimate_normals()
done: 52.405 seconds, 7 Mb allocated
Orients Normals with a Minimum Spanning Tree (k=18)...
Calls mst_orient_normals()
  7 Mb allocated
  Create Index_property_map
  Index_property_map: optimized version for a random access container
  mst_find_source()
  7 Mb allocated
  Creates KD-tree
  13 Mb allocated
  Creates Riemannian Graph
//From here (...) Never finishes!
 
Thanks a lot for all your help! 
 
Juliano Costa
 
2009/8/5 Manuel Caroli <>
Hi Juliano,

Juliano Costa wrote:
Hello again Manuel,
 Yes. By "surface" I was refearring to the convex hull (the outter side of the envelop points).
Note that you can use

incident_cells(infinite_vertex(), output_iterator) to get the cells that have the triangles of the convex hull as a facet.

 This new package for "Surface reconstruction" seems just GREAT.
It looks exactlly what I need to do.
I'm going to download the beta version to test it now!
 Just one more thing:
I was trying to to integrate the alpha shape with my current example.
Right now I have CGAL::Triangulation_vertex_base_with_info_3 in order to set the ->info() with my
index.
 For the alpha shape, If I really understood it, I must use CGAL::Alpha_shape_vertex_base_3 but this does not contain
the "info" field.
Is there any other way for me to set the "info"?
There should be an CGAL::Alpha_shape_vertex_base_with_info_3 file to do so, right?!
It should be possible to use them in a nested way, i.e.
Alpha_shape_vertex_base_3<Traits,Triangulation_vertex_base_with_info_3>

Maybe with the above mentioned approach to extract the convex hull you don't need the info anymore...

best

Manuel

 



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