[Insight-users] Upsampling B-spline grid in DeformableRegistration6.cxx

[Brecht Heyde]

Hi everyone, hi Luis,

I have been reading through 2 of your previous posts on the itk user list regarding the use of an upsampler with the BSplineResampleImageFunction and the BSplineDecompositionImageFilter, all for the purpose of upsampling the bspline grid.

These posts were (sorry for the ugly long links)
- http://itk-insight-users.2283740.n2.nabble.com/Follow-up-About-the-up-sampling-of-deformation-field-from-low-resolution-to-high-in-Examples-Deforma6-td4839712.html#none
- http://www.itk.org/pipermail/insight-users/2010-January/034976.html

As you were explaining: the output of the upsampler using the BSplineResampleImageFunction is the deformation field resulting represented by the bspline coefficient in a coarse bspline grid but sampled in more points (of the refined level). See lines 340-356 of DeformableRegistration6.cxx.

I was just wondering why the following line was not inserted (at line 346 for example) to reflect that the resampling process gives a deformation field linked to the original bspline grid with a custom bsplineorder (which may be different then the standard 3rd order):

function->SetSplineOrder(bSplineOrder); //originating from typedef itk::BSplineDeformableTransform<CoordRepType, Dimension, bSplineOrder> TransformType

Or am I still seeing this the wrong way?

Best regards,
Brecht