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math_QuaternionToAxisAngle now safe for small or close to 2pi rotations.

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Philip Eisenlohr 2010-04-29 10:01:09 +00:00
parent e8719cb6b8
commit 15e5dcf8f2
1 changed files with 10 additions and 17 deletions
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@ -1386,23 +1386,16 @@ pure function math_transpose3x3(A)
real(pReal) halfAngle, sinHalfAngle real(pReal) halfAngle, sinHalfAngle
real(pReal), dimension(4) :: math_QuaternionToAxisAngle real(pReal), dimension(4) :: math_QuaternionToAxisAngle
halfAngle=acos(Q(1)) halfAngle = dacos(Q(1)) ! value range 0 to 180 deg
sinHalfAngle=sin(halfAngle) sinHalfAngle = dsin(halfAngle)
math_QuaternionToAxisAngle(1)=Q(2)/sinHalfAngle if (sinHalfAngle <= 1.0e-4_pReal) then ! very small rotation angle?
math_QuaternionToAxisAngle(2)=Q(3)/sinHalfAngle math_QuaternionToAxisAngle = 0.0_pReal
math_QuaternionToAxisAngle(3)=Q(4)/sinHalfAngle else
! Remark: the above calculations gives problems math_QuaternionToAxisAngle(1:3) = Q(2:4)/sinHalfAngle
! for HalfAngle->0, i.e. for very small rotation angles math_QuaternionToAxisAngle(4) = halfAngle*2.0_pReal*inDeg
! and always at inrement 0 where identical orientations endif
! are compared in the calculation of the grainrotation;
! the correct interpretation of these special cases
! is left to the postprocessing.
! A possible integrity check would be to check for
! the unit length of the resulting axis.
math_QuaternionToAxisAngle(4)=halfAngle*2.0_pReal*inDeg
ENDFUNCTION ENDFUNCTION
!******************************************************************** !********************************************************************