[Insight-users] Confused with itkPointSetToPointSetRegistrationTest

[Dirk Hollstein]

Hello list,

I'd like to ask for help with the  
itkPointSetToPointSetRegistrationTest example in ITK  
(itkAlgorithmsTest2). Since I am new to registration, it is a very  
basic question:

We changed the Offset of the moving point set by setting the fixed x,  
resp. y component from 0 to 100, such introducing a real offset  
between the point sets:

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

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


When running the registration, the calculated distance is  
surprisingly about -75, not -100. So we changed the initial guess  
from identity to -100 by setting up an appropriate vector:

typedef itk::Vector<
double,
2  > VectorType;

VectorType aVector;

aVector[0] = -100.00;
aVector[1] = -100.00;


That still did not help to calculate the real distance, but left us  
confused. Next we changed the gradientTolerance, valueTolerance,  
epsilonFunction, but to no avail.

Are we tuning the wrong parameters? Any suggestions are welcome.

Thanks a lot in advance.

Regards,
Dirk