BRIX5

/*

    Inertial Measurement Unit Maths Library

    Copyright (C) 2013-2014  Samuel Cowen

        www.camelsoftware.com

    This program is free software: you can redistribute it and/or modify

    it under the terms of the GNU General Public License as published by

    the Free Software Foundation, either version 3 of the License, or

    (at your option) any later version.

    This program is distributed in the hope that it will be useful,

    but WITHOUT ANY WARRANTY; without even the implied warranty of

    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License

    along with this program.  If not, see <http://www.gnu.org/licenses/>.

*/

#ifndef IMUMATH_QUATERNION_HPP

#define IMUMATH_QUATERNION_HPP

#include <stdlib.h>

#include <string.h>

#include <stdint.h>

#include <math.h>

#include "matrix.h"

namespace imu

{

class Quaternion

{

public:

    Quaternion(): _w(1.0), _x(0.0), _y(0.0), _z(0.0) {}

    Quaternion(double w, double x, double y, double z):

        _w(w), _x(x), _y(y), _z(z) {}

    Quaternion(double w, Vector<3> vec):

        _w(w), _x(vec.x()), _y(vec.y()), _z(vec.z()) {}

    double& w()

    {

        return _w;

    }

    double& x()

    {

        return _x;

    }

    double& y()

    {

        return _y;

    }

    double& z()

    {

        return _z;

    }

    double w() const

    {

        return _w;

    }

    double x() const

    {

        return _x;

    }

    double y() const

    {

        return _y;

    }

    double z() const

    {

        return _z;

    }

    double magnitude() const

    {

        return sqrt(_w*_w + _x*_x + _y*_y + _z*_z);

    }

    void normalize()

    {

        double mag = magnitude();

        *this = this->scale(1/mag);

    }

    Quaternion conjugate() const

    {

        return Quaternion(_w, -_x, -_y, -_z);

    }

    void fromAxisAngle(const Vector<3>& axis, double theta)

    {

        _w = cos(theta/2);

        //only need to calculate sine of half theta once

        double sht = sin(theta/2);

        _x = axis.x() * sht;

        _y = axis.y() * sht;

        _z = axis.z() * sht;

    }

    void fromMatrix(const Matrix<3>& m)

    {

        double tr = m.trace();

        double S;

        if (tr > 0)

        {

            S = sqrt(tr+1.0) * 2;

            _w = 0.25 * S;

            _x = (m(2, 1) - m(1, 2)) / S;

            _y = (m(0, 2) - m(2, 0)) / S;

            _z = (m(1, 0) - m(0, 1)) / S;

        }

        else if (m(0, 0) > m(1, 1) && m(0, 0) > m(2, 2))

        {

            S = sqrt(1.0 + m(0, 0) - m(1, 1) - m(2, 2)) * 2;

            _w = (m(2, 1) - m(1, 2)) / S;

            _x = 0.25 * S;

            _y = (m(0, 1) + m(1, 0)) / S;

            _z = (m(0, 2) + m(2, 0)) / S;

        }

        else if (m(1, 1) > m(2, 2))

        {

            S = sqrt(1.0 + m(1, 1) - m(0, 0) - m(2, 2)) * 2;

            _w = (m(0, 2) - m(2, 0)) / S;

            _x = (m(0, 1) + m(1, 0)) / S;

            _y = 0.25 * S;

            _z = (m(1, 2) + m(2, 1)) / S;

        }

        else

        {

            S = sqrt(1.0 + m(2, 2) - m(0, 0) - m(1, 1)) * 2;

            _w = (m(1, 0) - m(0, 1)) / S;

            _x = (m(0, 2) + m(2, 0)) / S;

            _y = (m(1, 2) + m(2, 1)) / S;

            _z = 0.25 * S;

        }

    }

    void toAxisAngle(Vector<3>& axis, double& angle) const

    {

        double sqw = sqrt(1-_w*_w);

        if (sqw == 0) //it's a singularity and divide by zero, avoid

            return;

        angle = 2 * acos(_w);

        axis.x() = _x / sqw;

        axis.y() = _y / sqw;

        axis.z() = _z / sqw;

    }

    Matrix<3> toMatrix() const

    {

        Matrix<3> ret;

        ret.cell(0, 0) = 1-(2*(_y*_y))-(2*(_z*_z));

        ret.cell(0, 1) = (2*_x*_y)-(2*_w*_z);

        ret.cell(0, 2) = (2*_x*_z)+(2*_w*_y);

        ret.cell(1, 0) = (2*_x*_y)+(2*_w*_z);

        ret.cell(1, 1) = 1-(2*(_x*_x))-(2*(_z*_z));

        ret.cell(1, 2) = (2*(_y*_z))-(2*(_w*_x));

        ret.cell(2, 0) = (2*(_x*_z))-(2*_w*_y);

        ret.cell(2, 1) = (2*_y*_z)+(2*_w*_x);

        ret.cell(2, 2) = 1-(2*(_x*_x))-(2*(_y*_y));

        return ret;

    }

    // Returns euler angles that represent the quaternion.  Angles are

    // returned in rotation order and right-handed about the specified

    // axes:

    //

    //   v[0] is applied 1st about z (ie, roll)

    //   v[1] is applied 2nd about y (ie, pitch)

    //   v[2] is applied 3rd about x (ie, yaw)

    //

    // Note that this means result.x() is not a rotation about x;

    // similarly for result.z().

    //

    Vector<3> toEuler() const

    {

        Vector<3> ret;

        double sqw = _w*_w;

        double sqx = _x*_x;

        double sqy = _y*_y;

        double sqz = _z*_z;

        ret.x() = atan2(2.0*(_x*_y+_z*_w),(sqx-sqy-sqz+sqw));

        ret.y() = asin(-2.0*(_x*_z-_y*_w)/(sqx+sqy+sqz+sqw));

        ret.z() = atan2(2.0*(_y*_z+_x*_w),(-sqx-sqy+sqz+sqw));

        return ret;

    }

    Vector<3> toAngularVelocity(double dt) const

    {

        Vector<3> ret;

        Quaternion one(1.0, 0.0, 0.0, 0.0);

        Quaternion delta = one - *this;

        Quaternion r = (delta/dt);

        r = r * 2;

        r = r * one;

        ret.x() = r.x();

        ret.y() = r.y();

        ret.z() = r.z();

        return ret;

    }

    Vector<3> rotateVector(const Vector<2>& v) const

    {

        return rotateVector(Vector<3>(v.x(), v.y()));

    }

    Vector<3> rotateVector(const Vector<3>& v) const

    {

        Vector<3> qv(_x, _y, _z);

        Vector<3> t = qv.cross(v) * 2.0;

        return v + t*_w + qv.cross(t);

    }

    Quaternion operator*(const Quaternion& q) const

    {

        return Quaternion(

            _w*q._w - _x*q._x - _y*q._y - _z*q._z,

            _w*q._x + _x*q._w + _y*q._z - _z*q._y,

            _w*q._y - _x*q._z + _y*q._w + _z*q._x,

            _w*q._z + _x*q._y - _y*q._x + _z*q._w

        );

    }

    Quaternion operator+(const Quaternion& q) const

    {

        return Quaternion(_w + q._w, _x + q._x, _y + q._y, _z + q._z);

    }

    Quaternion operator-(const Quaternion& q) const

    {

        return Quaternion(_w - q._w, _x - q._x, _y - q._y, _z - q._z);

    }

    Quaternion operator/(double scalar) const

    {

        return Quaternion(_w / scalar, _x / scalar, _y / scalar, _z / scalar);

    }

    Quaternion operator*(double scalar) const

    {

        return scale(scalar);

    }

    Quaternion scale(double scalar) const

    {

        return Quaternion(_w * scalar, _x * scalar, _y * scalar, _z * scalar);

    }

private:

    double _w, _x, _y, _z;

};

} // namespace

#endif