On 2/27/08, <b class="gmail_sendername">Felix Bollenbeck</b> <<a href="mailto:bollen@ipk-gatersleben.de">bollen@ipk-gatersleben.de</a>> wrote:<div><span class="gmail_quote"></span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hello all,<br> <br> I have I question regarding the MultiResolutionImageRegistrationMethod<br> and passign the current-level parameter to the next level:<br> <br> At the end of one resolution level the transformparameters of the<br>
current level are stored:<br> <br> MultiResolutionImageRegistrationMethod.txx line 312:<br> <br> if ( m_CurrentLevel < m_NumberOfLevels - 1 )<br> {<br> m_InitialTransformParametersOfNextLevel =<br>
m_LastTransformParameters;<br> <br> And in the next level iteration these are used for intialization:<br> <br> MultiResolutionImageRegistrationMethod.txx line 108:<br> <br> m_Optimizer->SetInitialPosition(<br>
m_InitialTransformParametersOfNextLevel );<br> <br> I do not understandt how the transform parameters adapted to now larger<br> image <br></blockquote><div><br>Since most (see below) transforms in ITK represent transformations in
physical space and not in pixel space, nothing needs to be done to
adapt them to a higher resolution level. <br>
<br>
This is not true for several deformable transformations. For instance
if you used a deformation field, you would have to resample your
deformation field at each resolution from a lower resolution field.
Or, if you used itk::BSplineDeformableTransform, you would interpolate
a high resolution grid from a spline grid of lower resolution. In such
cases you would use itk::ImageRegistrationMethod instead of
itk::MultiresolutionImageRegistrationMethod and perform the
interpolation yourself. <br>
<br>
For most transforms, itk::MultiResolutionImageRegistrationMethod works just fine, no adaptation needed.<br><br>
HTH<br>
--<br>
karthik<br></div></div>