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<div>So to the question: &nbsp;&quot;Is this (./Registration/Common/include/itkCenteredVersorTransformInitializer)&nbsp;class useful?&quot; &nbsp;&nbsp;I think the answer is &quot;No&quot;.</div>
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<div>I think that the&nbsp;itkLandmarkBasedTransformInitializer.h class does &nbsp;initialize a 3D versor from a set of landmarks. &nbsp;In ITKv4 there is also support for initializing Affine transformations.</div>
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<div>Hans</div>
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<span style="font-weight:bold">From: </span>Bill Lorensen &lt;<a href="mailto:bill.lorensen@gmail.com">bill.lorensen@gmail.com</a>&gt;<br>
<span style="font-weight:bold">Date: </span>Sun, 23 Oct 2011 16:35:10 -0400<br>
<span style="font-weight:bold">To: </span>Hans Johnson &lt;<a href="mailto:hans-johnson@uiowa.edu">hans-johnson@uiowa.edu</a>&gt;<br>
<span style="font-weight:bold">Cc: </span>Dean Inglis &lt;<a href="mailto:dean.inglis@camris.ca">dean.inglis@camris.ca</a>&gt;, &quot;<a href="mailto:insight-users@itk.org">insight-users@itk.org</a>&quot; &lt;<a href="mailto:insight-users@itk.org">insight-users@itk.org</a>&gt;<br>
<span style="font-weight:bold">Subject: </span>Re: [Insight-users] initialize VersorRigid3DTransform<br>
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So how can we help Dean?<br>
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<div class="gmail_quote">On Sun, Oct 23, 2011 at 11:18 AM, Johnson, Hans J <span dir="ltr">
&lt;<a href="mailto:hans-johnson@uiowa.edu">hans-johnson@uiowa.edu</a>&gt;</span> wrote:<br>
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<div>Bill,</div>
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<div>In ITKv4 the &quot;Centered&quot; transforms are likely to be deprecated.</div>
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<div>Brian Avants and Luis Ibanez provided the following:</div>
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<li>Rationale for removing the CenteredTransforms</li></ol>
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<div style="font-family:Calibri; font-size:medium">The goal of the centered transforms was to attempt to optimize both the center of rotation and the transform parameters. &nbsp;This leads to a poorly posed optimization problem because, as one changes the center
 of rotation, the optimization landscape also changes leading to unstable performance. &nbsp;</div>
<div style="font-family:Calibri; font-size:medium">&nbsp;</div>
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<li>A recommended ITKv4 upgrade path for those using the centered transform</li></ol>
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<div style="font-family:Calibri; font-size:medium">If you were using the centered transforms, we recommend replacing the centered transform with its non-centered equivalent. &nbsp;Then, where one previously wrote:</div>
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<div style="font-family:Calibri; font-size:medium">transform-&gt;SetCenter(center)&nbsp;</div>
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<div style="font-family:Calibri; font-size:medium">one would now write&nbsp;</div>
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<div style="font-family:Calibri; font-size:medium">transform-&gt;SetFixedParameters(fixed_parameters)&nbsp;</div>
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<div style="font-family:Calibri; font-size:medium">where the fixed_parameters will depend on which transform is being used. &nbsp; For matrix transforms, this will be the center of rotation (check this) and may be equal to the image's origin. &nbsp; &nbsp;For dense mappings
 ( BSpline, displacement fields ) &nbsp;, this will be the image spacing, direction, origin. &nbsp;</div>
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<div style="font-family:Calibri; font-size:medium">Hans</div>
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<span style="font-weight:bold">From: </span>Bill Lorensen &lt;<a href="mailto:bill.lorensen@gmail.com" target="_blank">bill.lorensen@gmail.com</a>&gt;<br>
<span style="font-weight:bold">Date: </span>Sun, 23 Oct 2011 11:11:32 -0400<br>
<span style="font-weight:bold">To: </span>Dean Inglis &lt;<a href="mailto:dean.inglis@camris.ca" target="_blank">dean.inglis@camris.ca</a>&gt;<br>
<span style="font-weight:bold">Cc: </span>&lt;<a href="mailto:insight-users@itk.org" target="_blank">insight-users@itk.org</a>&gt;<br>
<span style="font-weight:bold">Subject: </span>Re: [Insight-users] initialize VersorRigid3DTransform<br>
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Is this class useful?<br>
./Registration/Common/include/itkCenteredVersorTransformInitializer<br>
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<div class="gmail_quote">On Sat, Oct 22, 2011 at 12:44 PM, Dean Inglis <span dir="ltr">
&lt;<a href="mailto:dean.inglis@camris.ca" target="_blank">dean.inglis@camris.ca</a>&gt;</span> wrote:<br>
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how can I initialize a VersorRigid3DTransform for a point set<br>
to image registration problem using the following information:<br>
1) center of the moving points, c<br>
2) principal axes of the moving points, e1, e2, e3<br>
3) center of the image calculated using the ImageMomentsCalculator, cofg<br>
4) principal axes of the image calculated using the ImageMomentsCalculator, p1, p2, p3<br>
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where all variables above are double arrays of size 3? &nbsp;Bascally, I would like<br>
to be able to initialize the transform:<br>
&nbsp; ParametersType parameters( transform-&gt;<u></u>GetNumberOfParameters() );<br>
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&nbsp;// &nbsp;Versor type<br>
&nbsp; typedef &nbsp; &nbsp;TransformType::VersorType &nbsp; &nbsp; &nbsp;VersorType;<br>
&nbsp; VersorType versor;<br>
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&nbsp; parameters[0] = versor.GetX(); &nbsp; // Rotations<br>
&nbsp; parameters[1] = versor.GetY();<br>
&nbsp; parameters[2] = versor.GetZ();<br>
&nbsp; parameters[3] = 0.0; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // Translations<br>
&nbsp; parameters[4] = 0.0;<br>
&nbsp; parameters[5] = 0.0;<br>
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&nbsp; transform-&gt;SetParameters( parameters );<br>
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but I dont know how the rotations should be initialized. &nbsp;I could calculate a 3x3 rotation<br>
matrix :<br>
A = e * p<br>
where e = {e1,e2,e3} and p = {p1,p2,p3} but how could that be used to initialize the<br>
transform?<br>
<br>
Dean <br>
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