[Insight-users] Need help with itkPointSetToPointSetRegistration

[Elena Pavlovskaia]

Hello Dirk,

I am not an expert in ITK so I might be wrong in what I say.

1. I tried your example, and I also got a wrong result. It was different
from your result though. My result was: ShiftInX = -2.29, ShiftInY
= -100.08. It's strange that your result is different. Did you see that
there are two for-loops for setting the moving points? Did you add offset in
both loops?

2. Per my understanding the LevenbergMarquardtOptimizer used in that example
is not a good choice for this task: it seems to be subject to local minima
and to be very slow. We are using the VTK vtkLandmarkTransform for the Point
Set to Point Set registration. It works very precisely and very fast.

Elena

---------------------------
Dirk Hollstein wrote:

Hello list,

I'd like to ask for help with the
itkPointSetToPointSetRegistrationTest example in ITK
(itkAlgorithmsTest2).

To understand how the example works, we changed the offset of the
moving point set by setting the fixed x, resp. y component from 0 to
100, such introducing an offset of 100 between the fixed and moving
point set:

point[0]=100;
point[1]=i;

instead of:
point[0]=0;
point[1]=i;   etc.


When running the registration with all other parameters unchanged,
the calculated distance is surprisingly about -75, not -100.

Next we changed the number of points, number of iterations,
gradientTolerance, valueTolerance, epsilonFunction, but none helped
to improve the result.
What can we do to register correctly? Any suggestions are welcome.

Thanks a lot in advance.

Regards,
Dirk