Hi Maarten,
Yes - if you change the last column to be 0 0 0 1 then you are
doing "no translation". However rotation and translation are
highly coupled, so when you say "no translation" what you actually
get is a rotation about the 0,0,0 voxel (which is in the corner of
the image) and may not be what you want. If you want to do a
rotation about a different centre, then you'll need to actually have
a non-zero translation. The way to work out the translation is:
trans = new_centre - rotation_matrix * old_centre
where the rotation_matrix has the 0 0 0 1 final column.
All the best,
Mark
On 19 Nov 2008, at 07:27, Maarten Versluis wrote:
> Dear all,
>
> I am struggling with the following problem:
>
> I have 2 volumes of the same person scanned with a different
> resolution. I want to register the low resolution image to the high
> resolution image, using a rigid body 6 DOF model.
> On a different dataset I would like apply only the found rotations
> and skip the translations. What would be the correct way of doing
> so? I was thinking of changing the last column of the rotation
> matrix to [0 0 0 1], is that correct?
> Many thanks in advance,
>
> Maarten
> Maarten Versluis
> Leiden University Medical Center
> Department of Radiology - C3Q
> Albinusdreef 2
> 2333 ZA Leiden
> The Netherlands
> E-mail: [log in to unmask]
>
|