[ITK] [ITK-users] itk exponential displacement field image filter

[Anja Ende]

Hello,

I have another question about the itk::
ExponentialDisplacementFieldImageFilter. Looking at the implementation, it
performs the exponentiation using the scaling and squaring approach.

The initial exponential is computed by doing a first order approximation.
However, it is done simply by dividing the input velocity field by the
factor 2^N

ie. exp(v_0) = v/2^N

However, I thought that the linear approximation of exponential of 'x'
where x is close to 0 is: 1+x. So, i thought that the expression should be:

ie. exp(v_0) = 1 + v/2^N

I saw the original Arsigny paper but could not figure this out. I am sure
this is a mistake in understanding on my part and would be very grateful if
someone can explain why this intercept term is not there?

Thanks,

Anja
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