Procedure

   void rotmat_c ( ConstSpiceDouble   m1[3][3], 
                   SpiceDouble        angle, 
                   SpiceInt           iaxis, 
                   SpiceDouble        mout[3][3] ) 

Abstract

 
   rotmat_c applies a rotation of angle radians about axis iaxis to a 
   matrix.  This rotation is thought of as rotating the coordinate 
   system. 
 

Required_Reading

 
   None. 
 

Keywords

 
   MATRIX,  ROTATION 
 

Brief_I/O

 
   VARIABLE  I/O  DESCRIPTION 
   --------  ---  -------------------------------------------------- 
   m1        I     Matrix to be rotated. 
   angle     I     Angle of rotation (radians). 
   iaxis     I     Axis of rotation (X=1, Y=2, Z=3). 
   mout      O     Resulting rotated matrix.
      

Detailed_Input

 
   m1      This is a matrix to which a rotation is to be applied. 
           In matrix algebra, the components of the matrix are 
           relative to one particular coordinate system. Applying 
           rotmat_c changes the components of m1 so that they are 
           relative to a rotated coordinate system. 

   angle   The angle in radians through which the original 
           coordinate system is to be rotated. 

   iaxis   An index for the axis of the original coordinate system 
           about which the rotation by angle is to be performed. 
           iaxis = 1,2 or 3 designates the x-, y- or z-axis, 
           respectively. 

Detailed_Output

 
   mout    The matrix resulting from the application of the 
           specified rotation to the input matrix m1.  If 
           
              [angle]         
                    iaxis 
                    
           denotes the rotation matrix by angle radians about iaxis,
           (see the Rotations Required Reading document) then mout is 
           given by the following matrix equation: 

              mout = [angle]      * m1 
                            iaxis 
                            
           mout can overwrite m1. 
 

Parameters

 
   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. 
 

Files

 
   None. 
 

Particulars

 
   None. 
 

Examples

 
   Suppose that to rotate the a set of inertial axes to body fixed 
   axes, one must first roll the coordinate axes about the x-axis by 
   angle r to get x', y', z'.  From this one must pitch about the 
   y' axis by angle o to get x'', y'', z''.  And finally yaw the 
   x'', y'', z'' about the z'' axis by angle y to obtain the 
   transformation to bodyfixed coordinates.  If id is the identity 
   matrix, then the following code fragment generates the 
   transformation from interitial to body fixed. 

      rotmat_c ( id, r, 1, m1   ); 
      rotmat_c ( m1, p, 2, m2   ); 
      rotmat_c ( m2, y, 3, tibf ); 
 

Restrictions

 
   None. 
 

Literature_References

 
   None. 
 

Author_and_Institution

 
   N.J. Bachman    (JPL)
   W.M. Owen       (JPL) 
   W.L. Taber      (JPL) 
 

Version

   
   -CSPICE Version 1.1.0, 22-OCT-1998 (NJB)

      Made input matrix const.

   -CSPICE Version 1.0.0, 08-FEB-1998 (NJB)
 
      Based on SPICELIB Version 1.0.1, 10-MAR-1992 (WLT)
   

Index_Entries

 
   rotate a matrix 
 

Link to routine rotmat_c source file rotmat_c.c