trackball.h Example File

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 #ifndef TRACKBALL_H
 #define TRACKBALL_H

 #include <QtWidgets>

 #include <QtGui/qvector3d.h>
 #include <QtGui/qquaternion.h>

 class TrackBall
 {
 public:
     enum TrackMode
     {
         Plane,
         Sphere,
     };
     TrackBall(TrackMode mode = Sphere);
     TrackBall(float angularVelocity, const QVector3D& axis, TrackMode mode = Sphere);
     // coordinates in [-1,1]x[-1,1]
     void push(const QPointF& p, const QQuaternion &transformation);
     void move(const QPointF& p, const QQuaternion &transformation);
     void release(const QPointF& p, const QQuaternion &transformation);
     void start(); // starts clock
     void stop(); // stops clock
     QQuaternion rotation() const;
 private:
     QQuaternion m_rotation;
     QVector3D m_axis;
     float m_angularVelocity;

     QPointF m_lastPos;
     QTime m_lastTime;
     bool m_paused;
     bool m_pressed;
     TrackMode m_mode;
 };

 #endif