[Insight-users] orientation of vectors of the coefficient image of a bsplineDeformableTransform

[Kristina Grunewald]

Hello everybody,

I am registering a circle (fixed image) and a square (moving image).
The square is smaller than the circle and their centers are superimposed.
The transform is BSPlineDeformableTransform and the metric MeanSquares.
This works well and results exactly in what I expect.

Except for:
I am writing the coefficient images of the bspline transform to a vector
image and then view it with paraview.
To do so I use 3d vectors having the z-component being set to zero and
a 3d image consisting of one slice.
Having a 2d image consisting of 2d vectors it isn't possible in
paraview to set the orient mode to vector when applying a glyph filter.
However, this seems to work well, too.
The only thing I am wondering about is the direction of the vectors:
I would have expected them to direct from the center of the image to its
borders.
This is only the case in y-direction.
In x-direction the vectors point from the the border to the center of
the image.

I attached my resulting coefficient image.

When I view the displacement field, the vectors are oriented in the same
way.

Could anybody explain to me what I am not getting?

Thanks,
Kristina

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