<div class="gmail_quote">On Fri, Mar 6, 2009 at 9:18 AM, Bryn Lloyd <span dir="ltr"><<a href="mailto:blloyd@vision.ee.ethz.ch">blloyd@vision.ee.ethz.ch</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hi Karthik,<br>
<br>
Thanks for the answer.<br>
<br>
The reason why I believe this is the case is that when I pass an image with spacings [0.1, 0.1, 0.5]mm I get distance value around 1.0mm, while corresponding distance values (from a distance map) are approx. 0.1mm.<br>
<br>
<br>
Actually, now I looked at the code in ReinitializeLevelSetImageFilter.txx.<br>
<br>
It does NOT set the OutputSpacing and Origin of the FastMarching object, i.e. this must be BUG.</blockquote><div><br>It should. That's a bug then :) Please file a report and it would be great if could submit a patch if you can. <br>
<br>Thanks<br>--<br>karthik<br><br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
<br>
--Bryn<br>
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Karthik Krishnan wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div class="im">
Bryn:<br>
<br>
I don't think that is true. The Reinitialize level set filter simply relies on the fast marching filter to generate the signed distance function. The fastmarching filter does take voxel anisotropicity into account when marching the level set front.<br>
<br>
See the lines involving the update equation in itkFastMarchingImageFilter.h<br>
<br>
const int axis = node.GetAxis();<br>
const double spaceFactor = vnl_math_sqr( 1.0 / spacing[axis] );<br>
const double value = double(node.GetValue());<br>
aa += spaceFactor;<br>
bb += value * spaceFactor;<br>
cc += vnl_math_sqr( value ) * spaceFactor;<br>
<br>
<br></div><div class="im">
On Fri, Mar 6, 2009 at 8:06 AM, Bryn Lloyd <<a href="mailto:blloyd@vision.ee.ethz.ch" target="_blank">blloyd@vision.ee.ethz.ch</a> <mailto:<a href="mailto:blloyd@vision.ee.ethz.ch" target="_blank">blloyd@vision.ee.ethz.ch</a>>> wrote:<br>
<br>
Hi all,<br>
<br>
Do I understand correctly that the ReinitializeLevelSetImageFilter<br>
does not use the spacing of the input image?<br>
<br>
If yes, I guess I need to resample the input image, in order to be<br>
isotropic AND scale the results in order to have Euclidean<br>
distances. Right?<br>
<br>
Thanks<br>
Bryn<br>
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-- <br>
Karthik Krishnan<br>
R&D Engineer,<br>
Kitware Inc.<br>
Ph: 518 371 3971 x119<br>
Fax: 518 371 3971<br>
</div></blockquote>
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<br>
-- <br>
-------------------------------------------------<br><font color="#888888">
Bryn Lloyd<br>
Computer Vision Laboratory<br>
ETH Zürich, Sternwartstrasse 7<br>
CH - 8092 Zürich, Switzerland<br>
Tel: +41 44 63 26668<br>
Fax: +41 44 63 21199<br>
-------------------------------------------------<br>
</font></blockquote></div><br><br clear="all"><br>-- <br>Karthik Krishnan<br>R&D Engineer,<br>Kitware Inc.<br>Ph: 518 371 3971 x119<br>Fax: 518 371 3971<br>