/*******************************************************************************
*                                                                              *
* Trick Simulation Environment Software                                        *
*                                                                              *
* Copyright (c) 1996,1997 LinCom Corporation, Houston, TX                      *
* All rights reserved.                                                         *
*                                                                              *
* Copyrighted by LinCom Corporation and proprietary to it. Any unauthorized    *
* use of Trick Software including source code, object code or executables is   *
* strictly prohibited and LinCom assumes no liability for such actions or      *
* results thereof.                                                             *
*                                                                              *
* Trick Software has been developed under NASA Government Contracts and        *
* access to it may be granted for Government work by the following contact:    *
*                                                                              *
* Contact: Charles Gott, Branch Chief                                          *
*          Simulation and Graphics Branch                                      *
*          Automation, Robotics, & Simulation Division                         *
*          NASA, Johnson Space Center, Houston, TX                             *
*                                                                              *
*******************************************************************************/
/* 
   PURPOSE: (Multiply 2 quaternions, q3 = q1*q2)

   REFERENCE: ((Flight Control - Ascent Flight Phase) (FSSR STS 83-0008A, Section 4.7.10 QUAT_MULT) (Volume 1, June 30, 
   1985))

   PROGRAMMERS: (((M Schira) (McDonnell Douglas) (Jan 1993) (v1.0) (Init Release)))

 */

/* 
 * $Id: quat_mult.c 49 2009-02-02 22:37:59Z lin $
 */

#include "../include/trick_math.h"

void quat_mult(double q3[4],    /* Out: quaternion */
               double q1[4],    /* In: quaternion */
               double q2[4])
{                                      /* In: quaternion */
    q3[0] = q1[0] * q2[0] - (q1[1] * q2[1] + q1[2] * q2[2] + q1[3] * q2[3]);
    q3[1] = q1[0] * q2[1] + q2[0] * q1[1] + q1[2] * q2[3] - q1[3] * q2[2];
    q3[2] = q1[0] * q2[2] + q2[0] * q1[2] + q1[3] * q2[1] - q1[1] * q2[3];
    q3[3] = q1[0] * q2[3] + q2[0] * q1[3] + q1[1] * q2[2] - q1[2] * q2[1];

    return;
}