Thanks for clarifying this bug, bezier splines guarantee continuity with value at derivative. I look forward to applying differentiable and continuous interpolation (with knot wise polarity) with this additional bug fix.
Best regards, Cartik Sharma http://about.me/sharmacartik On Wed, Apr 24, 2013 at 9:33 AM, <[email protected]> wrote: > Dear all,**** > > ** ** > > The BSplineInterpolateImageFunction class has two functions to compute > the derivative: > - EvaluateDerivativeAtContinuousIndex > - EvaluateValueAndDerivativeAtContinuousIndex**** > > The first one does take direction cosines into account, the other does > not. When called while using an image with non-trivial direction > cosines, the two derivatives are not equal.**** > > I believe this bug was introduced a long time ago by commit > 6abbc7969a90786c4c73f5d191f634db536c2d1d :**** > > ** ** > > > http://itk.org/gitweb?p=ITK.git;a=commitdiff;h=6abbc7969a90786c4c73f5d191f634db536c2d1d#patch13 > **** > > ** ** > > I attached a test program that simply calls the two functions. The input > of the test program (set with interpolator->SetInputImage() ) is an image > with direction cosines:**** > > (-0, 7.48376e-009, -1, 7.48376e-009, 1, 7.48376e-009, 1, -7.48376e-009, 0) > **** > > ** ** > > Current output:**** > > EvaluateDerivative: [42.7697, -9.97885, 22.2913]**** > > EvaluateValueAndDerivative: [-22.2913, -9.97885, 42.7697]**** > > But that should really be the same. Note that the first and third entry > are switched, and negated.**** > > ** ** > > I filed a gerrit entry which proposes a fix:**** > > http://review.source.kitware.com/#/c/11016/**** > > ** ** > > After that fix the output is as follows:**** > > EvaluateDerivative: [42.7697, -9.97885, 22.2913]**** > > EvaluateValueAndDerivative: [42.7697, -9.97885, 22.2913]**** > > So, equal as it should be.**** > > ** ** > > Looking forward to your feedback,**** > > Regards, Marius**** > > ** ** > > Marius Staring, PhD**** > > Division of Image Processing (LKEB)**** > > Department of Radiology**** > > Leiden University Medical Center**** > > PO Box 9600, 2300 RC Leiden, The Netherlands**** > > phone: +31 (0)71 526 2137, fax: +31 (0)71 524 8256**** > > [email protected]**** > > ** ** > > _______________________________________________ > Powered by www.kitware.com > > Visit other Kitware open-source projects at > http://www.kitware.com/opensource/opensource.html > > Kitware offers ITK Training Courses, for more information visit: > http://kitware.com/products/protraining.php > > Please keep messages on-topic and check the ITK FAQ at: > http://www.itk.org/Wiki/ITK_FAQ > > Follow this link to subscribe/unsubscribe: > http://www.itk.org/mailman/listinfo/insight-developers > > -- "There is plenty of room at the bottom!" R. Feynman
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