CreateRotMat.c

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/************************************************************************/
/**

   \file       CreateRotMat.c
   
   \version    V1.6R
   \date       27.09.95
   \brief      Simple matrix and vector operations
   
   \copyright  (c) UCL / Dr. Andrew C. R. Martin 1991-5
   \author     Dr. Andrew C. R. Martin
   \par
               Institute of Structural & Molecular Biology,
               University College London,
               Gower Street,
               London.
               WC1E 6BT.
   \par
               andrew@bioinf.org.uk
               andrew.martin@ucl.ac.uk
               
**************************************************************************

   This code is NOT IN THE PUBLIC DOMAIN, but it may be copied
   according to the conditions laid out in the accompanying file
   COPYING.DOC.

   The code may be modified as required, but any modifications must be
   documented so that the person responsible can be identified.

   The code may not be sold commercially or included as part of a 
   commercial product except as described in the file COPYING.DOC.

**************************************************************************

   Description:
   ============


**************************************************************************

   Usage:
   ======

**************************************************************************

   Revision History:
   =================
-  V1.0  06.09.91 Original
-  V1.0a 01.06.92 Documented
-  V1.1  30.09.92 Matrix multiplication added
-  V1.2  10.06.93 void return from matrix multiplication
-  V1.3  22.07.93 Added CreateRotMat()
-  V1.4  03.08.93 Changed matrix multiplication to standard direction
-  V1.5  28.07.95 Added VecDist()
-  V1.6  27.09.95 Added MatMult33_33()
-  V1.7  07.07.14 Use bl prefix for functions By: CTP

*************************************************************************/
/* Doxygen
   -------
   #GROUP    Maths
   #SUBGROUP Matrices
   #FUNCTION  blCreateRotMat()
   Create a 3x3 rotation matrix. Takes a direction as a single character
   ('x', 'y', or 'z'), an angle (in rads) and outputs a rotation matrix
*/
/************************************************************************/
/* Includes
*/
#include <math.h>
#include "MathType.h"

/************************************************************************/
/* Defines and macros
*/

/************************************************************************/
/* Globals
*/

/************************************************************************/
/* Prototypes
*/

/************************************************************************/
/*>void blCreateRotMat(char direction, REAL angle, REAL matrix[3][3])
   ------------------------------------------------------------------
*//**

   \param[in]     direction    Axis about which to rotate
   \param[in]     angle        Angle (in rads) to rotate
   \param[out]    matrix       Rotation matrix

   Create a 3x3 rotation matrix. Takes a direction as a single character
   ('x', 'y', or 'z'), an angle (in rads) and outputs a rotation matrix
   
-  22.07.93 Original    By: ACRM
-  07.07.14 Use bl prefix for functions By: CTP
*/
void blCreateRotMat(char direction, REAL angle, REAL matrix[3][3])
{
   int   i, j,
         m, 
         m1,
         m2;
   REAL  CosTheta,
         SinTheta;
         
   /* Initialise matrix to all 0.0                                      */
   for(i=0; i<3; i++)
      for(j=0; j<3; j++)
         matrix[i][j] = 0.0;
   
   /* Select the items that need to be filled in                        */
   switch(direction)
   {
   case 'x':   case 'X':
      m = 0;
      break;
   case 'y':   case 'Y':
      m = 1;
      break;
   case 'z':   case 'Z':
      m = 2;
      break;
   default:                   /* Just return the unit matrix            */
      for(i=0; i<3; i++)
         matrix[i][i] = 1.0;
      return;
   }
   
   /* Find which items these relate to                                  */
   m1 = (m+1)  % 3;
   m2 = (m1+1) % 3;
   
   /* Fill in the values                                                */
   matrix[m][m]   = 1.0;
   CosTheta       = (REAL)cos((double)angle);
   SinTheta       = (REAL)sin((double)angle);
   matrix[m1][m1] = CosTheta;
   matrix[m2][m2] = CosTheta;
   matrix[m1][m2] = SinTheta;
   matrix[m2][m1] = -SinTheta;
}