[Insight-users] GetCenter() ?

[Luis Ibanez]

Hi Tony,


Yes,

It is very likely that you are not setting
the Transform correctly.

Did you initialized the Center of the Transform ?

Please read the ITK Software Guide

   http://www.itk.org/ItkSoftwareGuide.pdf

in particular the sections related to the

    CenteredTransformInitializer

class.


Note, that for trivial registration problems,
the setting of the Transform center may not
be an issue. However, if you don't initialize
the center of rotation of the transform you are
challenging the optimizer to have a more difficult
path in the parametric space to get to the optimal
value of the Transform.

You should help the optimizer whenever you can.
Setting the center of rotation of the transform
is one of the easy things you can do that greatly
simplifies the job of the optimizer.



   Regards,



       Luis



-----------------
tony hakki wrote:
> hi Luis;
> Thanks for your reply,when I say  (finalTransform->GetCenter() );  it 
> gives me the result of (0,0,0). So does it shows that my registration is 
> processing incorrectly?
> 
> ----- Original Message ----
> From: Luis Ibanez <luis.ibanez at kitware.com>
> To: tony hakki <tony2007vtk at yahoo.com>
> Cc: insight-users at itk.org
> Sent: Tuesday, March 27, 2007 3:33:50 PM
> Subject: Re: [Insight-users] GetCenter() ?
> 
> Hi Tony,
> 
> Please read the ITK Software Guide:
> 
>     http://www.itk.org/ItkSoftwareGuide.pdf
> 
> There is a full section discussing the issue
> of Center of Rotation for Transforms in the
> context of image registration.
> 
> This is section: 8.6 "Centered Transforms".
> pdf-page 380.
> 
> To put it short:  The center of rotation is
> needed because in most image registration
> problems it is desirable to rotate around
> the center of the image extent and not
> around the center of the coordinate system
> origin.
> 
> You will find a related discussion in section 6.9.4
> "Resample Image Filter" in pdf-pages 254-285.
> 
> 
>     Regards,
> 
> 
>        Luis
> 
> 
> ----------------------
> tony hakki wrote:
>  > Hello;
>  >
>  > I have tried to implement point set to image registration
>  >
>  > What is the exact meaning of GetCenter(); in QuaternionRigidTransform
>  >
>  > ? When we write like that  
>  > finalTransform->SetCenter(finalTransform->GetCenter() ); What does 
> its mean?
>  >
>  > thank you
>  >
>  > Tony
>  >
>  >
>  >
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