Quaternion.h

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//-----------------------------------------------------------------------------
// File:     Quaternion.h
// Class:    Quaternion 
// Parent:   Vec4
// Purpose:  Quaternion (Euler parameters) for representing orientation
//-----------------------------------------------------------------------------
#ifndef SimTK_QUATERNION_H 
#define SimTK_QUATERNION_H 

/* -------------------------------------------------------------------------- *
 *                      SimTK Core: SimTK Simmatrix(tm)                       *
 * -------------------------------------------------------------------------- *
 * This is part of the SimTK Core biosimulation toolkit originating from      *
 * Simbios, the NIH National Center for Physics-Based Simulation of           *
 * Biological Structures at Stanford, funded under the NIH Roadmap for        *
 * Medical Research, grant U54 GM072970. See https://simtk.org.               *
 *                                                                            *
 * Portions copyright (c) 2005-7 Stanford University and the Authors.         *
 * Authors: Michael Sherman and Paul Mitiguy                                  *
 *                                                                            *
 * Permission is hereby granted, free of charge, to any person obtaining a    *
 * copy of this software and associated documentation files (the "Software"), *
 * to deal in the Software without restriction, including without limitation  *
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
 * and/or sell copies of the Software, and to permit persons to whom the      *
 * Software is furnished to do so, subject to the following conditions:       *
 *                                                                            *
 * The above copyright notice and this permission notice shall be included in *
 * all copies or substantial portions of the Software.                        *
 *                                                                            *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
 * THE AUTHORS, CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,    *
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR      *
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE  *
 * USE OR OTHER DEALINGS IN THE SOFTWARE.                                     *
 * -------------------------------------------------------------------------- */

//-----------------------------------------------------------------------------
#include "SimTKcommon/SmallMatrix.h"
#include "SimTKcommon/internal/UnitVec.h"
//-----------------------------------------------------------------------------
#include <iosfwd>  // Forward declaration of iostream
//-----------------------------------------------------------------------------


//-----------------------------------------------------------------------------
namespace SimTK {

//-----------------------------------------------------------------------------
// Forward declarations
class Rotation;


//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
class Quaternion : public Vec4 {
public:
    Quaternion() : Vec4(1,0,0,0) { }

    Quaternion( const Quaternion& q ) : Vec4(q) {}

    Quaternion& operator=( const Quaternion& q ) { Vec4::operator=( q.asVec4() );  return *this; }
    
    Quaternion( Real e0, Real e1, Real e2, Real e3 ) : Vec4(e0,e1,e2,e3)  { normalizeThis(); }
    explicit Quaternion( const Vec4& q ) : Vec4(q)                        { normalizeThis(); }

    SimTK_SimTKCOMMON_EXPORT explicit Quaternion( const Rotation& );

    void setQuaternionToZeroRotation()  { Vec4::operator=( Vec4(1,0,0,0) ); }
    void setQuaternionToNaN()           { Vec4::setToNaN(); }

    SimTK_SimTKCOMMON_EXPORT void  setQuaternionFromAngleAxis( const Vec4& av );
    SimTK_SimTKCOMMON_EXPORT void  setQuaternionFromAngleAxis( const Real& a, const UnitVec3& v );

    SimTK_SimTKCOMMON_EXPORT Vec4  convertQuaternionToAngleAxis() const;

    const Vec4&  asVec4() const  { return *static_cast<const Vec4*>(this); }

    Quaternion&  normalizeThis() { 
        const Real epsilon = std::numeric_limits<Real>::epsilon();
        const Real magnitude = Vec4::norm();
        if(      magnitude == 0      )  setQuaternionToZeroRotation();
        else if( magnitude < epsilon )  setQuaternionToNaN();
        else (*this) *= (1.0/magnitude);
        return *this;
    }

    Quaternion( const Vec4& v, bool ) : Vec4(v) {}

//----------------------------------------------------------------------------------------------------
// The following code is obsolete - it is here temporarily for backward compatibility (Mitiguy 10/13/2007)
//----------------------------------------------------------------------------------------------------
private:
    Vec4  convertToAngleAxis() const                          { return convertQuaternionToAngleAxis(); }
    void  setToAngleAxis( const Vec4& av )                    { setQuaternionFromAngleAxis(av); }
    void  setToAngleAxis( const Real& a, const UnitVec3& v )  { setQuaternionFromAngleAxis(a,v); }
    void setToNaN()                                           { setQuaternionToNaN(); }
    void setToZero()                                          { setQuaternionToZeroRotation(); }

};


//------------------------------------------------------------------------------
}  // End of namespace SimTK

//--------------------------------------------------------------------------
#endif // SimTK_QUATERNION_H_
//--------------------------------------------------------------------------