I am using the following example for my own purposes:
Below is an excerpt of the manual of ITK saying that the tree rotational parameters are not linear. Even below is the result of a successful registration (TFM file). It was extracted the region of interest (ROI) of two images and it was done the registration. And the operations of rotation and of shift of the transform of the TFM file were done on the original (bigger file from where it was taken the region of interest) moving image and it do not match with the bigger fixed image. The central points for rotation were converted from the Region of interest images to the bigger ones. (some other registrations worked). The central points of the ROI images are the geometry points (see the example).
Is there some distortion because the rotation parameters are no linear? If so how to proceed?
Thanks in Advance,
The itk::Euler3DTransform implements a rigid transformation in 3D space. It can be seen as
a rotation followed by a translation. This class exposes six parameters, three for the Euler angles
that represent the rotation and three for the translational components. This transform also allows the
users to set a specific center of rotation. The center coordinates are not modified during the optimization performed in a registration process. The main features of this transform are summarized in Table 3.12.
Three rotational parameters are non-linear and do not behave like Vector spaces. This must be taken
into account when selecting an optimizer to work with this transform and when fine tuning the
parameters of the optimizer.
#Insight Transform File V1.0
Parameters: 0.022339193565681897 -0.10614218282031297 -0.005968752506607872 0.5843942461161764 -2.447436642129231 -1.9773028691846155
FixedParameters: 76.64999999999999 74.85 54.6 0