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At 15/01/2001 15:57, Andrew Maclean wrote:<br>
<br>
<blockquote type=cite class=cite cite><font face="arial" size=2>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>
</font><br>
<font face="arial" size=2>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.
</font></blockquote><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 :)<br>
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