Home · All Namespaces · All Classes · Main Classes · Grouped Classes · Modules · Functions

trackball.cpp Example File
demos/boxes/trackball.cpp

 /****************************************************************************
 **
 ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
 ** Contact: Qt Software Information (qt-info@nokia.com)
 **
 ** This file is part of the demonstration applications of the Qt Toolkit.
 **
 ** 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 either Technology Preview License Agreement or the
 ** Beta Release License Agreement.
 **
 ** GNU General Public License Usage
 ** Alternatively, this file may be used under the terms of the GNU
 ** General Public License versions 2.0 or 3.0 as published by the Free
 ** Software Foundation and appearing in the file LICENSE.GPL included in
 ** the packaging of this file.  Please review the following information
 ** to ensure GNU General Public Licensing requirements will be met:
 ** http://www.fsf.org/licensing/licenses/info/GPLv2.html and
 ** http://www.gnu.org/copyleft/gpl.html.  In addition, as a special
 ** exception, Nokia gives you certain additional rights. These rights
 ** are described in the Nokia Qt GPL Exception version 1.3, included in
 ** the file GPL_EXCEPTION.txt in this package.
 **
 ** Qt for Windows(R) Licensees
 ** As a special exception, Nokia, as the sole copyright holder for Qt
 ** Designer, grants users of the Qt/Eclipse Integration plug-in the
 ** right for the Qt/Eclipse Integration to link to functionality
 ** provided by Qt Designer and its related libraries.
 **
 ** If you are unsure which license is appropriate for your use, please
 ** contact the sales department at qt-sales@nokia.com.
 **
 ****************************************************************************/

 #include "trackball.h"

 //============================================================================//
 //                                  TrackBall                                 //
 //============================================================================//

 TrackBall::TrackBall(TrackMode mode)
     : m_angularVelocity(0)
     , m_paused(false)
     , m_pressed(false)
     , m_mode(mode)
 {
     m_axis = gfx::Vector3f::vector(0, 1, 0);
     m_rotation = gfx::Quaternionf::quaternion(1.0f, 0.0f, 0.0f, 0.0f);
     m_lastTime = QTime::currentTime();
 }

 TrackBall::TrackBall(float angularVelocity, const gfx::Vector3f& axis, TrackMode mode)
     : m_axis(axis)
     , m_angularVelocity(angularVelocity)
     , m_paused(false)
     , m_pressed(false)
     , m_mode(mode)
 {
     m_rotation = gfx::Quaternionf::quaternion(1.0f, 0.0f, 0.0f, 0.0f);
     m_lastTime = QTime::currentTime();
 }

 void TrackBall::push(const QPointF& p, const gfx::Quaternionf &)
 {
     m_rotation = rotation();
     m_pressed = true;
     m_lastTime = QTime::currentTime();
     m_lastPos = p;
     m_angularVelocity = 0.0f;
 }

 void TrackBall::move(const QPointF& p, const gfx::Quaternionf &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 = delta.length() / msecs;
             m_axis = gfx::Vector3f::vector(delta.dy(), -delta.dx(), 0.0f).normalized();
             m_axis = transformation.transform(m_axis);
             m_rotation *= gfx::Quaternionf::rotation(delta.length(), m_axis);
         }
         break;
     case Sphere:
         {
             gfx::Vector3f lastPos3D = gfx::Vector3f::vector(m_lastPos.x(), m_lastPos.y(), 0);
             float sqrZ = 1 - lastPos3D.sqrNorm();
             if (sqrZ > 0)
                 lastPos3D[2] = sqrt(sqrZ);
             else
                 lastPos3D.normalize();

             gfx::Vector3f currentPos3D = gfx::Vector3f::vector(p.x(), p.y(), 0);
             sqrZ = 1 - currentPos3D.sqrNorm();
             if (sqrZ > 0)
                 currentPos3D[2] = sqrt(sqrZ);
             else
                 currentPos3D.normalize();

             m_axis = gfx::Vector3f::cross(currentPos3D, lastPos3D);
             float angle = asin(sqrt(m_axis.sqrNorm()));

             m_angularVelocity = angle / msecs;
             m_axis.normalize();
             m_axis = transformation.transform(m_axis);
             m_rotation *= gfx::Quaternionf::rotation(angle, m_axis);
         }
         break;
     }

     m_lastPos = p;
     m_lastTime = currentTime;
 }

 void TrackBall::release(const QPointF& p, const gfx::Quaternionf &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;
 }

 gfx::Quaternionf TrackBall::rotation() const
 {
     if (m_paused || m_pressed)
         return m_rotation;

     QTime currentTime = QTime::currentTime();
     float angle = m_angularVelocity * m_lastTime.msecsTo(currentTime);
     return m_rotation * gfx::Quaternionf::rotation(angle, m_axis);
 }


Copyright © 2009 Nokia Corporation and/or its subsidiary(-ies) Trademarks
Qt 4.5.0-rc1