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<p class=MsoNormal><span class=EmailStyle15><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'>If you
have the time, please </span></font></span><font color=navy><span
style='color:navy'>post your vtksbHausdorffDistanceToTarget class. I think that
that is the type of class that I am looking for!</span></font><font color=navy><span
style='color:navy;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'>Thankyou for the comments, they are very
useful and I will look at the vtksbIterativeClosestPointTransform because that is
the other aspect of this problem that is worrying me in this project. </span></font><font
color=navy><span style='color:navy;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'><![if !supportEmptyParas]> <![endif]></span></font><font
color=navy><span style='color:navy;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'>You have been most helpful.</span></font><font
color=navy><span style='color:navy;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'><![if !supportEmptyParas]> <![endif]></span></font><font
color=navy><span style='color:navy;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'>Thanks again </span></font><font
color=navy><span style='color:navy;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'><![if !supportEmptyParas]> <![endif]></span></font><font
color=navy><span style='color:navy;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'>Andrew</span></font><span
class=EmailStyle15><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'><o:p></o:p></span></font></span></p>
<p class=MsoNormal><span class=EmailStyle15><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></font></span></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=2 color=black
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;color:black'>-----Original
Message-----<br>
<b><span style='font-weight:bold'>From:</span></b> Sebastien BARRE
[mailto:seb-ml-vtk@barre.nom.fr]<br>
<b><span style='font-weight:bold'>Sent:</span></b> Tuesday, 16 January 2001
06:21<br>
<b><span style='font-weight:bold'>To:</span></b> a.maclean@acfr.usyd.edu.au<br>
<b><span style='font-weight:bold'>Cc:</span></b> vtkusers@public.kitware.com<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [vtkusers] Difference
between two surfaces.</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'>At 15/01/2001
15:57, Andrew Maclean wrote:<br>
<br style='mso-special-character:line-break'>
<![if !supportLineBreakNewLine]><br style='mso-special-character:line-break'>
<![endif]></span></font><font color=black><span style='color:black;mso-color-alt:
windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:36.0pt;mso-margin-top-alt:auto;
mso-margin-bottom-alt:auto;margin-left:72.0pt'><font size=2 color=black
face=Arial><span style='font-size:10.0pt;font-family:Arial;color:black'>If I
have a surface A, and a surface B, is it possible to generate a difference map
showing how much surface B differs from A.<br>
</span></font><font color=black><span style='color:black'><br>
</span></font><font size=2 color=black face=Arial><span style='font-size:10.0pt;
font-family:Arial;color:black'>I envisage A to be a reference map of some terrain
and B to the actual map of the terrain (say scanned by radar or laser). So I
want to calculate a height map showing the difference of B from A. I cannot
just subtract the height in A from B because it is unlikely that the
coordinates in A will match those sampled in B. </span></font><font
color=black><span style='color:black;mso-color-alt:windowtext'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt;color:black'><br>
Well, provided that both surfaces do not have the same topology, a naive
approach would be :<br>
<br>
a) Use some algorithm to first match both surfaces position and orientation (if
needed)<br>
b) then compute the Hausdorff distance between both.<br>
<br>
With VTK :<br>
<br>
a) I've posted a vtksbIterativeClosestPointTransform some weeks ago, check the
archive :) Use it to register/match both surfaces.<br>
<br>
b) If I find some time, I'll post my vtksbHausdorffDistanceToTarget class, but
it's actually very easy to implement (do not forget to use a vtkPointLocator
otherwise it takes forever).<br>
<br>
Hum, actually It might not be very satisfying because it computes distance
between points. So I guess you might also browse each point P of the surface A,
then find the intersection between the line L starting from that point P toward
the height direction, and the surface B. Do it also in the reverse direction.
It (vtkCellLocator) will return a coordinate on B that does not have to be a
point. Use that coordinate to compute the difference as a measure of the
distance between A and B.<br>
<br>
Good luck :)</span></font><font color=black><span style='color:black;
mso-color-alt:windowtext'><o:p></o:p></span></font></p>
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