demos/boxes/trackball.cpp

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  41
  42 #include "trackball.h"
  43 #include "scene.h"
  44
  45 //============================================================================//
  46 //                                  TrackBall                                 //
  47 //============================================================================//
  48
  49 TrackBall::TrackBall(TrackMode mode)
  50     : m_angularVelocity(0)
  51     , m_paused(false)
  52     , m_pressed(false)
  53     , m_mode(mode)
  54 {
  55     m_axis = QVector3D(0, 1, 0);
  56     m_rotation = QQuaternion();
  57     m_lastTime = QTime::currentTime();
  58 }
  59
  60 TrackBall::TrackBall(float angularVelocity, const QVector3D& axis, TrackMode mode)
  61     : m_axis(axis)
  62     , m_angularVelocity(angularVelocity)
  63     , m_paused(false)
  64     , m_pressed(false)
  65     , m_mode(mode)
  66 {
  67     m_rotation = QQuaternion();
  68     m_lastTime = QTime::currentTime();
  69 }
  70
  71 void TrackBall::push(const QPointF& p, const QQuaternion &)
  72 {
  73     m_rotation = rotation();
  74     m_pressed = true;
  75     m_lastTime = QTime::currentTime();
  76     m_lastPos = p;
  77     m_angularVelocity = 0.0f;
  78 }
  79
  80 void TrackBall::move(const QPointF& p, const QQuaternion &transformation)
  81 {
  82     if (!m_pressed)
  83         return;
  84
  85     QTime currentTime = QTime::currentTime();
  86     int msecs = m_lastTime.msecsTo(currentTime);
  87     if (msecs <= 20)
  88         return;
  89
  90     switch (m_mode) {
  91     case Plane:
  92         {
  93             QLineF delta(m_lastPos, p);
  94             m_angularVelocity = 180*delta.length() / (PI*msecs);
  95             m_axis = QVector3D(delta.dy(), -delta.dx(), 0.0f).normalized();
  96             m_axis = transformation.rotateVector(m_axis);
  97             m_rotation *= QQuaternion::fromAxisAndAngle(m_axis, delta.length());
  98         }
  99         break;
 100     case Sphere:
 101         {
 102             QVector3D lastPos3D = QVector3D(m_lastPos.x(), m_lastPos.y(), 0.0f);
 103             float sqrZ = 1 - QVector3D::dotProduct(lastPos3D, lastPos3D);
 104             if (sqrZ > 0)
 105                 lastPos3D.setZ(sqrt(sqrZ));
 106             else
 107                 lastPos3D.normalize();
 108
 109             QVector3D currentPos3D = QVector3D(p.x(), p.y(), 0.0f);
 110             sqrZ = 1 - QVector3D::dotProduct(currentPos3D, currentPos3D);
 111             if (sqrZ > 0)
 112                 currentPos3D.setZ(sqrt(sqrZ));
 113             else
 114                 currentPos3D.normalize();
 115
 116             m_axis = QVector3D::crossProduct(currentPos3D, lastPos3D);
 117             float angle = asin(sqrt(QVector3D::dotProduct(m_axis, m_axis)));
 118
 119             m_angularVelocity = 180*angle / (PI*msecs);
 120             m_axis.normalize();
 121             m_axis = transformation.rotateVector(m_axis);
 122             m_rotation *= QQuaternion::fromAxisAndAngle(m_axis, angle);
 123         }
 124         break;
 125     }
 126
 127
 128     m_lastPos = p;
 129     m_lastTime = currentTime;
 130 }
 131
 132 void TrackBall::release(const QPointF& p, const QQuaternion &transformation)
 133 {
 134     // Calling move() caused the rotation to stop if the framerate was too low.
 135     move(p, transformation);
 136     m_pressed = false;
 137 }
 138
 139 void TrackBall::start()
 140 {
 141     m_lastTime = QTime::currentTime();
 142     m_paused = false;
 143 }
 144
 145 void TrackBall::stop()
 146 {
 147     m_rotation = rotation();
 148     m_paused = true;
 149 }
 150
 151 QQuaternion TrackBall::rotation() const
 152 {
 153     if (m_paused || m_pressed)
 154         return m_rotation;
 155
 156     QTime currentTime = QTime::currentTime();
 157     float angle = m_angularVelocity * m_lastTime.msecsTo(currentTime);
 158     return m_rotation * QQuaternion::fromAxisAndAngle(m_axis, angle);
 159 }
 160