[Insight-users] affine transform without scaling?

[Luis Ibanez]

Hi Darren,

This looks like a very interesting problem.

Robert's advice is probably the first thing to try
(using the Rigid transform).

...Although...
you mentioned that you expect to have a deformation
on every slice...

Do you think that you actually will need shearing
and... maybe a BSpline deformation ?


      Luis


-------------------------------------------------------------------------------------------------
On Sat, Oct 24, 2009 at 11:16 PM, Darren Weber
<darren.weber.lists at gmail.com> wrote:
>
>
> On Sat, Oct 24, 2009 at 7:58 PM, Darren Weber <darren.weber.lists at gmail.com>
> wrote:
>>
>> Is there an easy way to turn off the scaling component of an affine
>> transform?
>>
>> Is there a method in itkAffineTransform to set the scale component to a
>> constant?
>>
>> Would you manually pull out the matrix, etc., modify it and then reset it
>> in the itkAffineTransform?
>>
>> TIA,
>> Darren
>>
>
> PS,  Maybe a geometric problem can help (or obscure) the problem.  Imagine a
> series of conic sections, starting at the tip of a cone and working down
> toward the base.  Each of these 2D conic sections needs to be registered
> into a 3D volume to recreate the cone.  If each section were a "pure"
> section taken along the axis from the tip to the center of the base, this
> would be fairly trivial as a rigid-body registration (probably no
> registration at all is required, just a known sequence of slices).  However,
> assume each section has an unknown deformation (but the series of sections
> is given in a known order).  If the affine registration starts at the tip
> (img001) and propagates all the way to the base (img100), the final diameter
> of the base section will be decreased to about the same diameter as the tip.
>
> The real problem is a series of microscopy images for a worm, which has a
> smaller diameter at the head and tail than in the body.
>
>
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