[Insight-users] ICP with kd-trees

[Bradley Lowekamp]

Hello,

I am not too familiar with this KDTree. But I recently added some indexing of the ITK Example in the doxygen, which includes cross linking between the examples and the class.

The KdTreeGenerator:

http://www.itk.org/Doxygen/html/classitk_1_1Statistics_1_1KdTreeGenerator.html

is used in the KdTree example:

http://www.itk.org/Doxygen/html/Statistics_2KdTree_8cxx-example.html

I hope this gives  you some additional insights.

Brad

On Aug 9, 2013, at 8:23 AM, Ramón Casero Cañas <rcasero at gmail.com> wrote:

> Dear all,
> 
> I'm trying to build an Iterative Closest Point algorithm with ITK.
> 
> I have googled advice on how it can be put together generally, and checked the three examples
> 
>    Insight/Examples/Registration/
>               IterativeClosestPoint1.cxx
>               IterativeClosestPoint2.cxx
>               IterativeClosestPoint3.cxx
> 
> recommended here
> 
> http://www.itk.org/pipermail/insight-users/2004-June/009092.html
> 
> These examples don't use kd-trees (the last ones uses a distance transform).
> 
> I have also found an example of a kd-tree, that however doesn't use point sets
> 
> http://www.itk.org/Wiki/ITK/Examples/Statistics/KdTree
> 
> I found an "itkPointLocator2.h" class developed for itkQuadEdgeMeshRigidRegistration in the ITK journal. I downloaded it from a more up-to-date publication that makes use of it, "Mesh Similarity Calculator" by Li and Magnotta (2010)
> 
> http://www.insight-journal.org/browse/publication/762
> 
> What I don't know is how to extract a metric from said locator, to pass it to the registration object.
> 
> This is the relevant part of the code I have so far
> 
> <CODE>
> PointSetType::Pointer fixedPointSet = PointSetType::New();
> PointSetType::Pointer movingPointSet = PointSetType::New();
> 
> // do something to read the points into the point sets
> 
>   // construct a Kd-tree structure for the reference point set, to
>   // accelerate the search for closest point
>   typedef itk::PointLocator2<PointSetType> PointLocatorType;
>   PointLocatorType::Pointer locator = PointLocatorType::New();
> 
>   locator->SetPointSet(fixedPointSet);
>   locator->Initialize(); // pre-compute the kd-tree structure
> </CODE>
> 
> I think I could get the metric from the kd-tree with something like
> 
> tree->GetDistanceMetric()
> 
> but I cannot get the tree from the locator, can I?
> 
> https://github.com/midas-journal/midas-journal-762/blob/master/QuadEdgeMeshRigidRegistration/Source/itkPointLocator2.h
> 
> Is this just a matter of adding a GetKdTree() method to itkPointLocator2.h, or is there some better solution to this?
> 
> 
> 
> Alternatively, if we not only have point sets at the input, but triangular meshes, it would be possible to compute shortest distances from the vertices of movingPointSet to a triangular mesh fixedTriMesh. This is efficient using an AABB tree (which can internally use a kd-tree), as in the CGAL library
> 
> http://www.cgal.org/Manual/latest/doc_html/cgal_manual/AABB_tree/Chapter_main.html
> 
> but this probably requires a vast amount of work? Or would it be relatively easy to write a new metric PointToTriMesh for ITK that imports CGAL AABB trees? I'm asking because I have no idea of how involved writing a new Metric class would be.
> 
> 
> Best regards,
> 
> Ramon.
> 
> 
> 
> 
> 
> 
> 
> 
> -- 
> Dr. Ramón Casero Cañas
> 
> Oxford e-Research Centre (OeRC)
> University of Oxford
> 7 Keble Rd
> Oxford OX1 3QG
> 
> tlf     +44 (0) 1865 610739
> web     http://www.cs.ox.ac.uk/people/Ramon.CaseroCanas
> photos  http://www.flickr.com/photos/rcasero/
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