mirror of
https://github.com/eddyem/BTA_lib.git
synced 2025-12-06 02:35:20 +03:00
75 lines
2.1 KiB
Fortran
75 lines
2.1 KiB
Fortran
SUBROUTINE sla_M2AV (RMAT, AXVEC)
|
|
*+
|
|
* - - - - -
|
|
* M 2 A V
|
|
* - - - - -
|
|
*
|
|
* From a rotation matrix, determine the corresponding axial vector
|
|
* (single precision)
|
|
*
|
|
* A rotation matrix describes a rotation about some arbitrary axis,
|
|
* called the Euler axis. The "axial vector" returned by this routine
|
|
* has the same direction as the Euler axis, and its magnitude is the
|
|
* amount of rotation in radians. (The magnitude and direction can be
|
|
* separated by means of the routine sla_VN.)
|
|
*
|
|
* Given:
|
|
* RMAT r(3,3) rotation matrix
|
|
*
|
|
* Returned:
|
|
* AXVEC r(3) axial vector (radians)
|
|
*
|
|
* The reference frame rotates clockwise as seen looking along
|
|
* the axial vector from the origin.
|
|
*
|
|
* If RMAT is null, so is the result.
|
|
*
|
|
* Last revision: 26 November 2005
|
|
*
|
|
* Copyright P.T.Wallace. All rights reserved.
|
|
*
|
|
* License:
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program (see SLA_CONDITIONS); if not, write to the
|
|
* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
|
|
* Boston, MA 02111-1307 USA
|
|
*
|
|
*-
|
|
|
|
IMPLICIT NONE
|
|
|
|
REAL RMAT(3,3),AXVEC(3)
|
|
|
|
REAL X,Y,Z,S2,C2,PHI,F
|
|
|
|
|
|
|
|
X = RMAT(2,3)-RMAT(3,2)
|
|
Y = RMAT(3,1)-RMAT(1,3)
|
|
Z = RMAT(1,2)-RMAT(2,1)
|
|
S2 = SQRT(X*X+Y*Y+Z*Z)
|
|
IF (S2.NE.0.0) THEN
|
|
C2 = (RMAT(1,1)+RMAT(2,2)+RMAT(3,3)-1.0)
|
|
PHI = ATAN2(S2/2.0,C2/2.0)
|
|
F = PHI/S2
|
|
AXVEC(1) = X*F
|
|
AXVEC(2) = Y*F
|
|
AXVEC(3) = Z*F
|
|
ELSE
|
|
AXVEC(1) = 0.0
|
|
AXVEC(2) = 0.0
|
|
AXVEC(3) = 0.0
|
|
END IF
|
|
|
|
END
|