[Insight-users] Rigid + Scale transform

[Vicente Grau]

I am trying to do a 3D registration combining a rigid transform with 
independent scaling in the three axes. The closest I've found in the 
library is the itkScaleSkewVersor3DTransform, so my idea was to use this 
as a base and remove the skew part, either by writing a new transform 
class or by introducing a factor with SetScale() that effectively 
eliminates this effect. I also thought about modifying 
QuaternionRigidTransform to allow for non-unit quaternions. What do you 
think is the best way to do this?
Furthermore, I guess I will need a special optimizer due to the 
parameters forming a non-vector space. Is there an optimizer that works 
with the ScaleSkewVersor3DTransform? Or, if not, how should I modify the 
existing optimizers (VersorRigid3DTransformOptimizer, I guess)?
Any help will be much appreciated!

Vicente Grau