quaternion.inl

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/*
    Sheep - A Rigid Body Dynamics Engine
    Copyright (C) 2001-2004 Francois Beaune
    Contact: http://toxicengine.sourceforge.net/

    This file is part of Sheep.

    Sheep 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 2 of the License, or
    (at your option) any later version.

    Sheep 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 Sheep; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

inline
Quaternion::Quaternion() {}

inline
Quaternion::Quaternion(const Quaternion &q) :
    m_s(q.m_s), m_v(q.m_v) {}

inline
Quaternion::Quaternion(Real s, const Vector3 &v) :
    m_s(s), m_v(v) {}

inline
Quaternion Quaternion::Identity() {
    return Quaternion(1.0, 0.0);
}

inline
Quaternion Quaternion::Rotation(Real angle, const Vector3 &axis) {
    const Real half_angle = 0.5 * angle;

    //!\todo Assume that axis is already a normalized vector.
    return Quaternion(
        cos(half_angle),
        sin(half_angle) * axis.Normalized());
}

inline
Quaternion Quaternion::Rotation(const Vector3 &from, const Vector3 &to) {
    return Quaternion(from * to, from ^ to);
}

inline
Quaternion &Quaternion::operator=(const Quaternion &q) {
    m_s = q.m_s;
    m_v = q.m_v;

    return *this;
}

inline
Quaternion Quaternion::operator+(const Quaternion &q) const {
    return Quaternion(m_s + q.m_s, m_v + q.m_v);
}

inline
Quaternion Quaternion::operator-(const Quaternion &q) const {
    return Quaternion(m_s - q.m_s, m_v - q.m_v);
}

inline
Quaternion Quaternion::operator-() const {
    return Quaternion(-m_s, -m_v);
}

inline
Quaternion Quaternion::operator*(Real r) const {
    return Quaternion(m_s * r, m_v * r);
}

inline
Quaternion Quaternion::operator/(Real r) const {
    const Real inv_r = 1.0 / r;

    return Quaternion(m_s * inv_r, m_v * inv_r);
}

inline
Quaternion &Quaternion::operator+=(const Quaternion &q) {
    m_s += q.m_s;
    m_v += q.m_v;

    return *this;
}

inline
Quaternion &Quaternion::operator-=(const Quaternion &q) {
    m_s -= q.m_s;
    m_v -= q.m_v;

    return *this;
}

inline
Quaternion &Quaternion::operator*=(Real r) {
    m_s *= r;
    m_v *= r;

    return *this;
}

inline
Quaternion &Quaternion::operator/=(Real r) {
    Real inv_r = 1.0 / r;

    m_s *= inv_r;
    m_v *= inv_r;

    return *this;
}

inline
Quaternion Quaternion::operator*(const Quaternion &q) const {
    return Quaternion(
        m_s * q.m_s - m_v * q.m_v,
        m_s * q.m_v + q.m_s * m_v + (m_v ^ q.m_v));
}

inline
Quaternion &Quaternion::operator*=(const Quaternion &q) {
    const Real s1 = m_s * q.m_s - m_v * q.m_v;

    m_v = m_s * q.m_v + q.m_s * m_v + (m_v ^ q.m_v);
    m_s = s1;

    return *this;
}

inline
Quaternion Quaternion::Conjugate() const {
    return Quaternion(m_s, -m_v);
}

inline
Quaternion Quaternion::Inverse() const {
    return Conjugate() / SquareNorm();
}

inline
Real Quaternion::SquareNorm() const {
    return m_s * m_s + m_v * m_v;
}

inline
Real Quaternion::Norm() const {
    return sqrt(SquareNorm());
}

inline
Quaternion Quaternion::Normalized() const {
    const Real n = Norm();
    return n == 0.0 ? Identity() : *this / n;
}

inline
Quaternion operator*(Real r, const Quaternion &q) {
    return q * r;
}

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