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#include "trackball.h"

#include "scene.h"

//============================================================================//

//                                  TrackBall                                 //

//============================================================================//

TrackBall::TrackBall(TrackMode mode)

    : m_angularVelocity(0)

    , m_paused(false)

    , m_pressed(false)

    , m_mode(mode)

{

    m_axis = QVector3D(0, 1, 0);

    m_rotation = QQuaternion();

    m_lastTime = QTime::currentTime();

}

TrackBall::TrackBall(float angularVelocity, const QVector3D& axis, TrackMode mode)

    : m_axis(axis)

    , m_angularVelocity(angularVelocity)

    , m_paused(false)

    , m_pressed(false)

    , m_mode(mode)

{

    m_rotation = QQuaternion();

    m_lastTime = QTime::currentTime();

}

void TrackBall::push(const QPointF& p, const QQuaternion &)

{

    m_rotation = rotation();

    m_pressed = true;

    m_lastTime = QTime::currentTime();

    m_lastPos = p;

    m_angularVelocity = 0.0f;

}

void TrackBall::move(const QPointF& p, const QQuaternion &transformation)

{

    if (!m_pressed)

        return;

    QTime currentTime = QTime::currentTime();

    int msecs = m_lastTime.msecsTo(currentTime);

    if (msecs <= 20)

        return;

    switch (m_mode) {

    case Plane:

        {

            QLineF delta(m_lastPos, p);

            m_angularVelocity = 180*delta.length() / (PI*msecs);

            m_axis = QVector3D(-delta.dy(), delta.dx(), 0.0f).normalized();

            m_axis = transformation.rotatedVector(m_axis);

            m_rotation = QQuaternion::fromAxisAndAngle(m_axis, 180 / PI * delta.length()) * m_rotation;

        }

        break;

    case Sphere:

        {

            QVector3D lastPos3D = QVector3D(m_lastPos.x(), m_lastPos.y(), 0.0f);

            float sqrZ = 1 - QVector3D::dotProduct(lastPos3D, lastPos3D);

            if (sqrZ > 0)

                lastPos3D.setZ(sqrt(sqrZ));

            else

                lastPos3D.normalize();

            QVector3D currentPos3D = QVector3D(p.x(), p.y(), 0.0f);

            sqrZ = 1 - QVector3D::dotProduct(currentPos3D, currentPos3D);

            if (sqrZ > 0)

                currentPos3D.setZ(sqrt(sqrZ));

            else

                currentPos3D.normalize();

            m_axis = QVector3D::crossProduct(lastPos3D, currentPos3D);

            float angle = 180 / PI * asin(sqrt(QVector3D::dotProduct(m_axis, m_axis)));

            m_angularVelocity = angle / msecs;

            m_axis.normalize();

            m_axis = transformation.rotatedVector(m_axis);

            m_rotation = QQuaternion::fromAxisAndAngle(m_axis, angle) * m_rotation;

        }

        break;

    }

    m_lastPos = p;

    m_lastTime = currentTime;

}

void TrackBall::release(const QPointF& p, const QQuaternion &transformation)

{

    // Calling move() caused the rotation to stop if the framerate was too low.

    move(p, transformation);

    m_pressed = false;

}

void TrackBall::start()

{

    m_lastTime = QTime::currentTime();

    m_paused = false;

}

void TrackBall::stop()

{

    m_rotation = rotation();

    m_paused = true;

}

QQuaternion TrackBall::rotation() const

{

    if (m_paused || m_pressed)

        return m_rotation;

    QTime currentTime = QTime::currentTime();

    float angle = m_angularVelocity * m_lastTime.msecsTo(currentTime);

    return QQuaternion::fromAxisAndAngle(m_axis, angle) * m_rotation;

}