[Insight-users] about TPS and EBS

[David Gobbi]

Hi Zhang,

I'm interested in this too, since I'm partially responsible for the
VTK TPS implementation.  Note that when you use the VTK TPS
you should specify which basis function to use, either R() or
R2LogR().  I'm not sure which one ITK uses by default, it is
possible that ITK automatically selects the correct basis function
depending on the dimensionality of the transformation.

 - David

--
  David Gobbi, MSc                       dgobbi@irus.rri.ca
  Advanced Imaging Research Group
  Robarts Research Institute, University of Western Ontario

On Mon, 18 Mar 2002, Luis Ibanez wrote:

>
> Hi Zhangzhijun,
>
> ITK ThinPlateSpline and ElasticBody splines are implemented
> using a common framework under the class itk::KernelTransform.
>
> This classes have not been optimized for speed yet.  So, it expected
> that VTK's version could be running faster.  We are interested in
> pushing performance to the same level anyways      :-)
>
>
> However,
> 1) The numerical results should be the same between itk and vtk
> 2) The time of execution for itk::TPS and itk::EBS should be the
>     same because the Point transformation is done by a common
>     code in KernelTransform. If you found EBS to be slower than
>     the TPS... there should be a problem with the code or with the
>     use of the class.
>
> Did you made this comparison in a compact application that you
> could send to us ?
>
> Otherwise we can make some tests in our side in order to identify
> time consumption. One of the suspect things done in KernelTransfom
> is the common extraction of submatrices from the WMatrix, which
> can be a costly operation.
>
>
> I'll look in to that.
>
>
> Thanks
>
> Luis
>
> ========================================================
>
> zhangzhijun wrote:
>
> >
> >
> > Dear all:
> >
> >         I want to use the thin plate spline and elastic body spline
> > implementation in itk
> >
> > but I found that the speed of the thin plate spline is very slow, much
> > slower than
> >
> > that in VTK and the ebs is even slower, also, the result is different
> > with VTK.
> >
> > I use totally 80 point for a 181*217*181 data warp, I dont' know
> > whether the number
> >
> > of points for the warp is ok.
> >
> >
> >
> >
> >
> > regards,
> >
> > zhang zhijun
> >
>
>
>
>
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