[Insight-users] cubic b-spline question

[Luca Pamparana]

Hello everyone,

I have been using the BSplineDeformableTransform class to parameterize
a deformation field using cubic b-splines. I have a couple of doubts
regarding cubic B-splines themselves and I was wondering if someone on
this forum would be kind enough to answer a couple of questions as
people here are knowledgeable about this:

- I see that the transformation at any given voxel is affected by the
neighboring 64 control points. However, say I take one control point
and just displace it along one dimension, how many voxels would this
affect i.e. how many voxels would see some changed displacement as a
result of moving one control point in one dimension?

- Is there a way in the ITK machinery to get the indexes of affected
voxels due to perturbation to a single b-spline control point in the
grid?

I would be very grateful if someone can shed some light onto this.

Many thanks,

Luca