[Insight-users] Jacobian of an affine transform

[francois rousseau]

Hi there,

I’m trying to check itkDisplacementFieldJacobianDeterminantFilter for affine transform and I get weird results.

Basically, I’ve created a simple affine transform with a scale factor in x dimension :

#Insight Transform File V1.0
#Transform 0
Transform: MatrixOffsetTransformBase_double_3_3
Parameters: 1.5 0 0 0 1 0 0 0 1 0 0 0 
FixedParameters: 22.6774 -12.4914 6.04305

I’ve converted this affine file to a deformation field using ComposeMultiTransform (from ANTS). The field is correct so far.

Then, I computed the jacobian of the field using itkDisplacementFieldJacobianDeterminantFilter.
Jacobian is constant and equal to 1.

I would have expected 1.5 or 2/3.

Am I doing something wrong?


Thanks
François


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