[Insight-users] rotating with itkVersorTransform

[J. Pura]

Hello,

I am trying to rotate a binary 3D blob relative to the principal axis of
another blob. The principal axes have been computed and have the following
unit vectors Blob1: <0.7171, -0.6963, -0.0296> and Blob2: <0.8658, -0.4995,
-0.0316>. Blob 1 is rotated. I used the Versor Transform, and in order to
initialize it, I found the angle between the two vectors = 0.2473 radians,
as well as the rotation axis, by finding the unit normal to the two vectors.
Then I followed the equation in a previous post by Luis Ibanez, which
suggested setting the parameters to Ax * sin ( T/2), etc... where Ax, Ay, Az
= the x,y,z components of the unit normal, and T = 0.2473 rad. I plugged
these values in, but the resulting image seems to have only been rotated
counter-clockwise "about the z-axis" (I understand that it's not a purely
z-rotation, but the final image seems to have been rotated slice by slice on
the xy plane). Is there anything wrong in my setup of the parameters? Also I
made sure to set the center of rotation to the centroid of Blob1. Any help
on this issue is much appreciated.

Best,

J. Pura
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