CGAL users discussion list

[Simon Giraudot <>]

Hello,

The documented function "get_inner_point()" returns the vertex of the 
underlying Delaunay 3D Triangulation (where the Poisson function is 
stored) where the Poisson function is minimum. What you are asking for, 
if I understand correctly, is to identify as many inner points as there 
are connected components. I think this is achievable by iterating on 
each Delaunay vertex that has a Poisson function value under 0 (or under 
the wanted threshold, usually the median value at input points), then 
separate these vertices by connected components on the triangulation, 
and finally just return one point per connected component.

I don't think you can achieve that with the documented API. However, 
some undocumented functions in the Poisson package may help: the class 
Poisson_reconstruction_function has a method "tr()" that returns a const 
ref the underlying triangulation. Using that, you can access the 
vertices of the triangulation which have a method "f()" that returns the 
value of the Poisson function. See the files 
"Poisson_reconstruction_function.h" and 
"Reconstruction_triangulation_3.h" for the undocumented 
classes/functions (they are still commented / internally documented for 
most of them).

Let me know if this is clear and if I can help any further.

Best,

--
Simon Giraudot, PhD
R&D Engineer
GeometryFactory - http://geometryfactory.com/

Le 02/08/2019 à 01:12, Gaetan a écrit :
> Hi all,
>
> I want to perform a Poisson reconstruction of an oriented point cloud that
> represents several disjoint smooth closed surfaces.
> Furthermore, I assume that the surfaces are not mutually included.
> To recover several disjoint surfaces I need to add at least one point per
> connected component to the c2t3 object (see  this post
> <http://cgal-discuss.949826.n4.nabble.com/About-the-surface-mesh-generator-tt952799.html#a952801>
> ).
> However, I do not know the number of connected components nor do I know
> where they are located.
> Inserting all the points in the c2t3 allows to recover all the components
> but this leads to an oversampled and un-smooth surface mesh.
>
> So far, I have thought of a workaround where I would mesh the opposite of
> the Poisson implicit function within the bounding sphere of the point cloud.
> This means that instead of meshing a set of disjoint smooth closed surfaces
> I would mesh a sphere with disjoint holes.
> The final step would be to extract the holes as a set of disjoint smooth
> closed surfaces.
>
> Nonetheless, I am wondering if there is not a better way to do this.
> For example, could we detect the connected components when computing the
> Poisson implicit function, and ultimately extract one point per connected
> component?
>
>
> Thanks for your help,
> Gaetan
>
>
>
> --
> Sent from: http://cgal-discuss.949826.n4.nabble.com/