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<h1 class="title">trackball.cpp Example File</h1>
<span class="subtitle">graphicsview/boxes/trackball.cpp</span>
<!-- $$$graphicsview/boxes/trackball.cpp-description -->
<div class="descr"> <a name="details"></a>
<pre class="cpp">

  <span class="comment">/****************************************************************************
  **
  ** Copyright (C) 2016 The Qt Company Ltd.
  ** Contact: https://www.qt.io/licensing/
  **
  ** This file is part of the demonstration applications of the Qt Toolkit.
  **
  ** $QT_BEGIN_LICENSE:BSD$
  ** Commercial License Usage
  ** Licensees holding valid commercial Qt licenses may use this file in
  ** accordance with the commercial license agreement provided with the
  ** Software or, alternatively, in accordance with the terms contained in
  ** a written agreement between you and The Qt Company. For licensing terms
  ** and conditions see https://www.qt.io/terms-conditions. For further
  ** information use the contact form at https://www.qt.io/contact-us.
  **
  ** BSD License Usage
  ** Alternatively, you may use this file under the terms of the BSD license
  ** as follows:
  **
  ** &quot;Redistribution and use in source and binary forms, with or without
  ** modification, are permitted provided that the following conditions are
  ** met:
  **   * Redistributions of source code must retain the above copyright
  **     notice, this list of conditions and the following disclaimer.
  **   * Redistributions in binary form must reproduce the above copyright
  **     notice, this list of conditions and the following disclaimer in
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  **   * Neither the name of The Qt Company Ltd nor the names of its
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  **     from this software without specific prior written permission.
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  **
  ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  ** &quot;AS IS&quot; AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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  ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.&quot;
  **
  ** $QT_END_LICENSE$
  **
  ****************************************************************************/</span>

  <span class="preprocessor">#include &quot;trackball.h&quot;</span>
  <span class="preprocessor">#include &quot;scene.h&quot;</span>
  <span class="preprocessor">#include &lt;qmath.h&gt;</span>
  <span class="preprocessor">#include &lt;cmath&gt;</span>

  <span class="comment">//============================================================================//</span>
  <span class="comment">//                                  TrackBall                                 //</span>
  <span class="comment">//============================================================================//</span>

  TrackBall<span class="operator">::</span>TrackBall(TrackMode mode)
      : m_angularVelocity(<span class="number">0</span>)
      <span class="operator">,</span> m_paused(<span class="keyword">false</span>)
      <span class="operator">,</span> m_pressed(<span class="keyword">false</span>)
      <span class="operator">,</span> m_mode(mode)
  {
      m_axis <span class="operator">=</span> QVector3D(<span class="number">0</span><span class="operator">,</span> <span class="number">1</span><span class="operator">,</span> <span class="number">0</span>);
      m_rotation <span class="operator">=</span> <span class="type"><a href="../qtgui/qquaternion.html">QQuaternion</a></span>();
      m_lastTime <span class="operator">=</span> <span class="type"><a href="../qtcore/qtime.html">QTime</a></span><span class="operator">::</span>currentTime();
  }

  TrackBall<span class="operator">::</span>TrackBall(<span class="type">float</span> angularVelocity<span class="operator">,</span> <span class="keyword">const</span> QVector3D<span class="operator">&amp;</span> axis<span class="operator">,</span> TrackMode mode)
      : m_axis(axis)
      <span class="operator">,</span> m_angularVelocity(angularVelocity)
      <span class="operator">,</span> m_paused(<span class="keyword">false</span>)
      <span class="operator">,</span> m_pressed(<span class="keyword">false</span>)
      <span class="operator">,</span> m_mode(mode)
  {
      m_rotation <span class="operator">=</span> <span class="type"><a href="../qtgui/qquaternion.html">QQuaternion</a></span>();
      m_lastTime <span class="operator">=</span> <span class="type"><a href="../qtcore/qtime.html">QTime</a></span><span class="operator">::</span>currentTime();
  }

  <span class="type">void</span> TrackBall<span class="operator">::</span>push(<span class="keyword">const</span> <span class="type"><a href="../qtcore/qpointf.html">QPointF</a></span><span class="operator">&amp;</span> p<span class="operator">,</span> <span class="keyword">const</span> <span class="type"><a href="../qtgui/qquaternion.html">QQuaternion</a></span> <span class="operator">&amp;</span>)
  {
      m_rotation <span class="operator">=</span> rotation();
      m_pressed <span class="operator">=</span> <span class="keyword">true</span>;
      m_lastTime <span class="operator">=</span> <span class="type"><a href="../qtcore/qtime.html">QTime</a></span><span class="operator">::</span>currentTime();
      m_lastPos <span class="operator">=</span> p;
      m_angularVelocity <span class="operator">=</span> <span class="number">0.0f</span>;
  }

  <span class="type">void</span> TrackBall<span class="operator">::</span>move(<span class="keyword">const</span> <span class="type"><a href="../qtcore/qpointf.html">QPointF</a></span><span class="operator">&amp;</span> p<span class="operator">,</span> <span class="keyword">const</span> <span class="type"><a href="../qtgui/qquaternion.html">QQuaternion</a></span> <span class="operator">&amp;</span>transformation)
  {
      <span class="keyword">if</span> (<span class="operator">!</span>m_pressed)
          <span class="keyword">return</span>;

      <span class="type"><a href="../qtcore/qtime.html">QTime</a></span> currentTime <span class="operator">=</span> <span class="type"><a href="../qtcore/qtime.html">QTime</a></span><span class="operator">::</span>currentTime();
      <span class="type">int</span> msecs <span class="operator">=</span> m_lastTime<span class="operator">.</span>msecsTo(currentTime);
      <span class="keyword">if</span> (msecs <span class="operator">&lt;</span><span class="operator">=</span> <span class="number">20</span>)
          <span class="keyword">return</span>;

      <span class="keyword">switch</span> (m_mode) {
      <span class="keyword">case</span> Plane:
          {
              <span class="type"><a href="../qtcore/qlinef.html">QLineF</a></span> delta(m_lastPos<span class="operator">,</span> p);
              <span class="keyword">const</span> <span class="type">float</span> angleDelta <span class="operator">=</span> <a href="../qtcore/qtmath.html#qRadiansToDegrees-1">qRadiansToDegrees</a>(<span class="type">float</span>(delta<span class="operator">.</span>length()));
              m_angularVelocity <span class="operator">=</span> angleDelta <span class="operator">/</span> msecs;
              m_axis <span class="operator">=</span> QVector3D(<span class="operator">-</span>delta<span class="operator">.</span>dy()<span class="operator">,</span> delta<span class="operator">.</span>dx()<span class="operator">,</span> <span class="number">0.0f</span>)<span class="operator">.</span>normalized();
              m_axis <span class="operator">=</span> transformation<span class="operator">.</span>rotatedVector(m_axis);
              m_rotation <span class="operator">=</span> <span class="type"><a href="../qtgui/qquaternion.html">QQuaternion</a></span><span class="operator">::</span>fromAxisAndAngle(m_axis<span class="operator">,</span> angleDelta) <span class="operator">*</span> m_rotation;
          }
          <span class="keyword">break</span>;
      <span class="keyword">case</span> Sphere:
          {
              QVector3D lastPos3D <span class="operator">=</span> QVector3D(m_lastPos<span class="operator">.</span>x()<span class="operator">,</span> m_lastPos<span class="operator">.</span>y()<span class="operator">,</span> <span class="number">0.0f</span>);
              <span class="type">float</span> sqrZ <span class="operator">=</span> <span class="number">1</span> <span class="operator">-</span> QVector3D<span class="operator">::</span>dotProduct(lastPos3D<span class="operator">,</span> lastPos3D);
              <span class="keyword">if</span> (sqrZ <span class="operator">&gt;</span> <span class="number">0</span>)
                  lastPos3D<span class="operator">.</span>setZ(std<span class="operator">::</span>sqrt(sqrZ));
              <span class="keyword">else</span>
                  lastPos3D<span class="operator">.</span>normalize();

              QVector3D currentPos3D <span class="operator">=</span> QVector3D(p<span class="operator">.</span>x()<span class="operator">,</span> p<span class="operator">.</span>y()<span class="operator">,</span> <span class="number">0.0f</span>);
              sqrZ <span class="operator">=</span> <span class="number">1</span> <span class="operator">-</span> QVector3D<span class="operator">::</span>dotProduct(currentPos3D<span class="operator">,</span> currentPos3D);
              <span class="keyword">if</span> (sqrZ <span class="operator">&gt;</span> <span class="number">0</span>)
                  currentPos3D<span class="operator">.</span>setZ(std<span class="operator">::</span>sqrt(sqrZ));
              <span class="keyword">else</span>
                  currentPos3D<span class="operator">.</span>normalize();

              m_axis <span class="operator">=</span> QVector3D<span class="operator">::</span>crossProduct(lastPos3D<span class="operator">,</span> currentPos3D);
              <span class="type">float</span> angle <span class="operator">=</span> <a href="../qtcore/qtmath.html#qRadiansToDegrees-1">qRadiansToDegrees</a>(std<span class="operator">::</span>asin(m_axis<span class="operator">.</span>length()));

              m_angularVelocity <span class="operator">=</span> angle <span class="operator">/</span> msecs;
              m_axis<span class="operator">.</span>normalize();
              m_axis <span class="operator">=</span> transformation<span class="operator">.</span>rotatedVector(m_axis);
              m_rotation <span class="operator">=</span> <span class="type"><a href="../qtgui/qquaternion.html">QQuaternion</a></span><span class="operator">::</span>fromAxisAndAngle(m_axis<span class="operator">,</span> angle) <span class="operator">*</span> m_rotation;
          }
          <span class="keyword">break</span>;
      }

      m_lastPos <span class="operator">=</span> p;
      m_lastTime <span class="operator">=</span> currentTime;
  }

  <span class="type">void</span> TrackBall<span class="operator">::</span>release(<span class="keyword">const</span> <span class="type"><a href="../qtcore/qpointf.html">QPointF</a></span><span class="operator">&amp;</span> p<span class="operator">,</span> <span class="keyword">const</span> <span class="type"><a href="../qtgui/qquaternion.html">QQuaternion</a></span> <span class="operator">&amp;</span>transformation)
  {
      <span class="comment">// Calling move() caused the rotation to stop if the framerate was too low.</span>
      move(p<span class="operator">,</span> transformation);
      m_pressed <span class="operator">=</span> <span class="keyword">false</span>;
  }

  <span class="type">void</span> TrackBall<span class="operator">::</span>start()
  {
      m_lastTime <span class="operator">=</span> <span class="type"><a href="../qtcore/qtime.html">QTime</a></span><span class="operator">::</span>currentTime();
      m_paused <span class="operator">=</span> <span class="keyword">false</span>;
  }

  <span class="type">void</span> TrackBall<span class="operator">::</span>stop()
  {
      m_rotation <span class="operator">=</span> rotation();
      m_paused <span class="operator">=</span> <span class="keyword">true</span>;
  }

  <span class="type"><a href="../qtgui/qquaternion.html">QQuaternion</a></span> TrackBall<span class="operator">::</span>rotation() <span class="keyword">const</span>
  {
      <span class="keyword">if</span> (m_paused <span class="operator">|</span><span class="operator">|</span> m_pressed)
          <span class="keyword">return</span> m_rotation;

      <span class="type"><a href="../qtcore/qtime.html">QTime</a></span> currentTime <span class="operator">=</span> <span class="type"><a href="../qtcore/qtime.html">QTime</a></span><span class="operator">::</span>currentTime();
      <span class="type">float</span> angle <span class="operator">=</span> m_angularVelocity <span class="operator">*</span> m_lastTime<span class="operator">.</span>msecsTo(currentTime);
      <span class="keyword">return</span> <span class="type"><a href="../qtgui/qquaternion.html">QQuaternion</a></span><span class="operator">::</span>fromAxisAndAngle(m_axis<span class="operator">,</span> angle) <span class="operator">*</span> m_rotation;
  }

</pre>
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<!-- @@@graphicsview/boxes/trackball.cpp -->
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