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50
51#include "trackball.h"
52#include "scene.h"
53
54//============================================================================//
55// TrackBall //
56//============================================================================//
57
58TrackBall::TrackBall(TrackMode mode)
59 : TrackBall(0, QVector3D(0, 1, 0), mode)
60{
61}
62
63TrackBall::TrackBall(float angularVelocity, const QVector3D& axis, TrackMode mode)
64 : m_axis(axis)
65 , m_angularVelocity(angularVelocity)
66 , m_mode(mode)
67{}
68
69void TrackBall::push(const QPointF& p, const QQuaternion &)
70{
71 m_rotation = rotation();
72 m_pressed = true;
73 m_lastTime = QTime::currentTime();
74 m_lastPos = p;
75 m_angularVelocity = 0.0f;
76}
77
78void TrackBall::move(const QPointF& p, const QQuaternion &transformation)
79{
80 if (!m_pressed)
81 return;
82
83 QTime currentTime = QTime::currentTime();
84 int msecs = m_lastTime.msecsTo(currentTime);
85 if (msecs <= 20)
86 return;
87
88 switch (m_mode) {
89 case Plane:
90 {
91 QLineF delta(m_lastPos, p);
92 const float angleDelta = qRadiansToDegrees(radians: float(delta.length()));
93 m_angularVelocity = angleDelta / msecs;
94 m_axis = QVector3D(-delta.dy(), delta.dx(), 0.0f).normalized();
95 m_axis = transformation.rotatedVector(vector: m_axis);
96 m_rotation = QQuaternion::fromAxisAndAngle(axis: m_axis, angle: angleDelta) * m_rotation;
97 }
98 break;
99 case Sphere:
100 {
101 QVector3D lastPos3D = QVector3D(m_lastPos.x(), m_lastPos.y(), 0.0f);
102 float sqrZ = 1 - QVector3D::dotProduct(v1: lastPos3D, v2: lastPos3D);
103 if (sqrZ > 0)
104 lastPos3D.setZ(std::sqrt(x: sqrZ));
105 else
106 lastPos3D.normalize();
107
108 QVector3D currentPos3D = QVector3D(p.x(), p.y(), 0.0f);
109 sqrZ = 1 - QVector3D::dotProduct(v1: currentPos3D, v2: currentPos3D);
110 if (sqrZ > 0)
111 currentPos3D.setZ(std::sqrt(x: sqrZ));
112 else
113 currentPos3D.normalize();
114
115 m_axis = QVector3D::crossProduct(v1: lastPos3D, v2: currentPos3D);
116 float angle = qRadiansToDegrees(radians: std::asin(x: m_axis.length()));
117
118 m_angularVelocity = angle / msecs;
119 m_axis.normalize();
120 m_axis = transformation.rotatedVector(vector: m_axis);
121 m_rotation = QQuaternion::fromAxisAndAngle(axis: m_axis, angle) * m_rotation;
122 }
123 break;
124 }
125
126
127 m_lastPos = p;
128 m_lastTime = currentTime;
129}
130
131void TrackBall::release(const QPointF& p, const QQuaternion &transformation)
132{
133 // Calling move() caused the rotation to stop if the framerate was too low.
134 move(p, transformation);
135 m_pressed = false;
136}
137
138void TrackBall::start()
139{
140 m_lastTime = QTime::currentTime();
141 m_paused = false;
142}
143
144void TrackBall::stop()
145{
146 m_rotation = rotation();
147 m_paused = true;
148}
149
150QQuaternion TrackBall::rotation() const
151{
152 if (m_paused || m_pressed)
153 return m_rotation;
154
155 QTime currentTime = QTime::currentTime();
156 float angle = m_angularVelocity * m_lastTime.msecsTo(currentTime);
157 return QQuaternion::fromAxisAndAngle(axis: m_axis, angle) * m_rotation;
158}
159
160

source code of qtbase/examples/widgets/graphicsview/boxes/trackball.cpp