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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hi VTK Users,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>In vtkMath.cxx, line 1766, the square root is taken of the sum of squares. (vtk 5.6.0)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>We think that this produces wrong matrices in case the input quaternion is not normalized.<o:p></o:p></p><p class=MsoNormal>The correct formula would be the same, just without the sqrt().<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>We have verified this correction with this matlab function:<o:p></o:p></p><p class=MsoNormal>http://www.csse.uwa.edu.au/~pk/Research/MatlabFns/Rotations/quaternion2matrix.m<o:p></o:p></p><p class=MsoNormal>vtkMath.cxx produces the same matrices only if the sqrt() is taken away.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Could someone with write permission have a look and maybe fix this in the VTK repository?<o:p></o:p></p><p class=MsoNormal>I'm happy to help with further testing if needed.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks,<o:p></o:p></p><p class=MsoNormal>Tamas<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>