Issue in using TransformRigidityPenalty Metrics alongwith the Mask where rigidity is to be imposed

[anmolnamdev]

Hi
I have been trying to use the TransformRigidityPenalty metric for my image registration task in which I am trying to impose a rigidity constraint in some part of the 3D volume, for which I am also providing a mask. But when I try to register using these settings, the mask doesn't seems to work. The mask is not having any effect on the registered output.
Anyone have any idea of How to use the Transform Rigidity Penalty to impose rigidity in some part of a 3D volume.
Urgent help needed Please.