trackball.cpp Example File

 /****************************************************************************
 **
 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
 ** All rights reserved.
 ** Contact: Nokia Corporation ([email protected])
 **
 ** This file is part of the demonstration applications of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:LGPL$
 ** No Commercial Usage
 ** This file contains pre-release code and may not be distributed.
 ** You may use this file in accordance with the terms and conditions
 ** contained in the Technology Preview License Agreement accompanying
 ** this package.
 **
 ** GNU Lesser General Public License Usage
 ** Alternatively, this file may be used under the terms of the GNU Lesser
 ** General Public License version 2.1 as published by the Free Software
 ** Foundation and appearing in the file LICENSE.LGPL included in the
 ** packaging of this file.  Please review the following information to
 ** ensure the GNU Lesser General Public License version 2.1 requirements
 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
 **
 ** In addition, as a special exception, Nokia gives you certain additional
 ** rights.  These rights are described in the Nokia Qt LGPL Exception
 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
 **
 ** If you have questions regarding the use of this file, please contact
 ** Nokia at [email protected].
 **
 **
 **
 **
 **
 **
 **
 **
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 #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;
 }