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new: math_QuaternionToAxisAngle

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Claudio Zambaldi 2010-04-12 11:07:25 +00:00
parent adf6206b71
commit 653837046e
1 changed files with 32 additions and 0 deletions
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@ -1413,6 +1413,38 @@ pure function math_transpose3x3(A)
ENDFUNCTION
!********************************************************************
! axis-angle (x, y, z, ang in deg) from quaternion (w+ix+jy+kz)
!********************************************************************
PURE FUNCTION math_QuaternionToAxisAngle(Q)
use prec, only: pReal, pInt
implicit none
real(pReal), dimension(4), intent(in) :: Q
real(pReal) halfAngle, sinHalfAngle
real(pReal), dimension(4) :: math_QuaternionToAxisAngle
halfAngle=acos(Q(1))
sinHalfAngle=sin(halfAngle)
math_QuaternionToAxisAngle(1)=Q(2)/sinHalfAngle
math_QuaternionToAxisAngle(2)=Q(3)/sinHalfAngle
math_QuaternionToAxisAngle(3)=Q(4)/sinHalfAngle
! Remark: the above calculations gives problems
! for HalfAngle->0, i.e. for very small rotation angles
! and always at inrement 0 where identical orientations
! 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
!****************************************************************
! rotation matrix from axis and angle (in radians)
!****************************************************************