[vtkusers] vtkQuaternionToMatrix3x3 needs verification or correction!

[Tamas Ungi]

Hi VTK Users,

 

In vtkMath.cxx, line 1766, the square root is taken of the sum of squares.
(vtk 5.6.0)

 

We think that this produces wrong matrices in case the input quaternion is
not normalized.

The correct formula would be the same, just without the sqrt().

 

We have verified this correction with this matlab function:

http://www.csse.uwa.edu.au/~pk/Research/MatlabFns/Rotations/quaternion2matri
x.m

vtkMath.cxx produces the same matrices only if the sqrt() is taken away.

 

Could someone with write permission have a look and maybe fix this in the
VTK repository?

I'm happy to help with further testing if needed.

 

Thanks,

Tamas

 

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