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rotate_c

 Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input Detailed_Output Parameters Exceptions Files Particulars Examples Restrictions Literature_References Author_and_Institution Version Index_Entries

Procedure

rotate_c ( Generate a rotation matrix )

void rotate_c ( SpiceDouble     angle,
SpiceInt        iaxis,
SpiceDouble     mout )

Abstract

Calculate the 3x3 rotation matrix generated by a rotation
of a specified angle about a specified axis. This rotation
is thought of as rotating the coordinate system.

None.

MATRIX
ROTATION

Brief_I/O

VARIABLE  I/O  DESCRIPTION
--------  ---  --------------------------------------------------
angle      I   Angle of rotation (radians).
iaxis      I   Axis of rotation (X=1, Y=2, Z=3).
mout       O   Resulting rotation matrix [angle]
iaxis

Detailed_Input

angle       is the angle given in radians, through which the rotation
is performed.

iaxis       is the index of the axis of rotation. The X, Y, and Z
axes have indices 1, 2 and 3 respectively.

Detailed_Output

mout        is the rotation matrix which describes the rotation of the
axis whose index is iaxis.

None.

Exceptions

Error free.

1)  If the axis index is not in the range 1 to 3, it will be
treated the same as that integer 1, 2, or 3 that is congruent
to it mod 3.

None.

Particulars

A rotation about the first, i.e. x-axis, is described by

|  1        0          0      |
|  0   cos(theta) sin(theta)  |
|  0  -sin(theta) cos(theta)  |

A rotation about the second, i.e. y-axis, is described by

|  cos(theta)  0  -sin(theta)  |
|      0       1        0      |
|  sin(theta)  0   cos(theta)  |

A rotation about the third, i.e. z-axis, is described by

|  cos(theta) sin(theta)   0   |
| -sin(theta) cos(theta)   0   |
|       0          0       1   |

rotate_c decides which form is appropriate according to the value
of IAXIS.

Examples

If rotate_c is called from a C program as follows:

rotate_c ( pi_c()/4, 3, mout );

then mout will be given by

| sqrt(2)/2   sqrt(2)/2   0  |
mout = |-sqrt(2)/2   sqrt(2)/2   0  |
|     0           0       1  |

None.

None.

Author_and_Institution

N.J. Bachman        (JPL)
J. Diaz del Rio     (ODC Space)

Version

-CSPICE Version 1.0.1, 04-AUG-2021 (JDR)

Edited the header to comply with NAIF standard.

-CSPICE Version 1.0.0, 08-FEB-1998 (NJB)

Based on SPICELIB Version 1.0.1, 10-MAR-1992 (WLT)

Index_Entries

generate a rotation matrix
Fri Dec 31 18:41:11 2021