[Insight-users] Initializing transform in pointset registration

[Karthik Krishnan]

The CenteredTransformIntializer class, as the doxygen documentation
mentions, is meant to be templated on Images, not PointSets.

There is no class in ITK that will help you with initializing your
transform, although there are registration methods such as ICP.

If you do not have any correspondances between the point-sets ( I assume you
don't ), you can compute a crude rigid-transform initialization yourself by
computing the centroids of the two point sets and the Eigen Vectors of the
two pointsets and then finding a transform that maps the axes (defined by
the eigen vectors, with the centroid as the origin) onto each other.

HTH
--
Karthik Krishnan
R&D Engineer,
Kitware Inc.

On 1/7/08, Juan Pedro de Miguel Porta <elkily69 at hotmail.com> wrote:
>
> Hello,
> I've found some problems setting the initial transform in my pointset to
> pointset registration application.
> When I looked in the software guide I found 2 different ways to solve this
> problem.
> First it was with this method:  transform->SetTranslation(centerMoving -
> centerFixed) as in the imageregistration5.cxx example, but it doesn't work
> because 'GetSpacing()','GetOrigin()' and 'GetSize()' are not applicable into
> pointsets.
> The other one was using the CenteredTransformInitializer class as in the
> imageregistration6.cxx example but when I tried to use it with pointsets
> instead of with fixed and moving images it also didn't work.This is the
> code:
>
> typedef itk::CenteredTransformInitializer < TransformType , PointSetType ,
> PointSetType> TransformInitializerType;
> TransformInitializerType::Pointer initializer =
> TransformInitializerType::New();
>
> My questions are:
> 1) Am I missing something and one of this methods should work? How can I
> do it?
> 2) And if not, is there any other way to initialize the transform?
>
> Thanks.
>
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