[vtkusers] vtkProcrustesAlignmentFilter error in centroid size

[Tim Hutton]

David,

Looking at the code now I'm not sure why we put that sqrt() in there. It 
would make sense *after* the for loop, ie:

   S += vtkMath::Distance2BetweenPoints(p,cp);
}
return sqrt(S);

Or perhaps more efficiently, leave it out all together and have 
CentroidSize (or CentroidSize2) return the square of the centroid size.

Rasmus and I are looking into this. Thankyou for noticing this!

For users of vtkProcrustesAlignmentFilter, CentroidSize is only called when 
using a similarity alignment.

Tim.

At 17:50 10/05/2003 +0930, David Netherway wrote:
>The procedure CentroidSize below returns the sum of the distances from
>points to the centroid instead of the square root of the sum of squared
>distances.
>This is contrary to my understanding of the centroid size. Is this an error
>or deliberate?
>
>David Netherway
>
>Module: $RCSfile: vtkProcrustesAlignmentFilter.cxx,v $
>
>Date: $Date: 2003/03/11 15:19:30 $
>
>Version: $Revision: 1.10 $
>
>// Calculate the centroid size of a point cloud
>
>static inline double CentroidSize(vtkPoints* pd, float *cp)
>
>{
>
>Centroid(pd, cp);
>
>
>double S = 0;
>
>for (int i = 0; i < pd->GetNumberOfPoints(); i++)
>
>{
>
>float *p = pd->GetPoint(i);
>
>
>S += sqrt(vtkMath::Distance2BetweenPoints(p,cp));
>
>}
>
>
>return S;
>
>}
>
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Tim Hutton,                        http://www.eastman.ucl.ac.uk/~dmi/MINORI
Research Fellow & PhD student,                   T.Hutton at eastman.ucl.ac.uk
MINORI Project, Biomedical Informatics Unit,
Eastman Dental Institute, UCL,                   Tel: [+44] (0)20 7915 2344
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