[ITK-users] AffineTransform to 4x4 matrix...again maybe

[vincent ngai]

Hi all, apologies if this has been asked before, I googled the above but
only got 4x4 -> AffineTransform and not the other way around.

I need to get the output of an AffineTransform after registration to my
OpenGL renderer.

>From what I understand, the AffineTransform is composed of a Rotation,
Center of Rotation and Translation.

So would the following sequence of 4x4 transformation be correct?

OGLM = InvCRM * Rot * CRM * TM

where

CRM      = 4x4 identity matrix with indices [ 12, 13, 14] set to XYZ value
of GetCenter()
InvCRM  = Inverse of CRM
Rot        = 4x4 Identity matrix with 3x3 set to the rotation parameters
TM        = 4x4 identity matrix with indicies[ 12, 13, 14 ] set to the
translation parameters

Essentially:

1) translate center to origin
2) perform rotation
3) translate back to where we were
4) slap on translation

I am doing the above, but for some reason the translation does not match
up. The rotation seems fine.
-- 
Regards,
Vincent
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