[Insight-users] derivative calculation

[Luis Ibanez]

Hi Michael,


Thanks for pointing this out.


This actually qualifies as a bug. It has been
entered in the bug tracker with ID # 843
http://www.itk.org/Bug/bug.php?op=show&bugid=843&pos=0


As you pointed out it will be more appropriate to
have a SetDelta()/GetDelta() methods for setting
the value of differential to be used for computing
the derivative. This value was fixed in good faith  :-)
under the assumption that the values to optimizer are
in the [-1:1] range. In practice, there is no way
for the Metric to enforce this range...

The scaling parameters are in practice applied to
the optimizer, where they are taken into account.

--

This bug has now been fixed.

Please update your CVS checkout in order to get
the modifications.

Let us know if you find any other problem.



   Thanks



      Luis


---------------
Michael wrote:

> Hi,
> 
> I've noticed, that the for the derivative calculation, the 
> MeanReciprocalSquareDifferenceImageToImageMetric and the 
> GradientDifferenceImageToImageMetric make uses of a fix-coded (0.00011) 
> delta for their derivative calculation. It seems to me, that the 
> HistogramImageToImageMetric uses a flexible derivative step length and 
> scalings for each parameters dimension for the same thing. I hope I 
> understood this correctely...
> 
> Is there a reason for the fix coded 0.00011 delta, and why 0.00011?
> 
> Thanks,
> 
> Michael
> 
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