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<title>libQGLViewer animation example</title>
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<h1>The animation example</h1>
<center>
<img src="../images/animation.jpg" width="300" height="200" alt="animation"/>
</center>
<p>
The <code>animate()</code> function illustrated by a water particle simulation.
</p>
<p>
When animation is activated (the Return key toggles animation), the <code>animate()</code> and
then the <code>draw()</code> functions are called in an infinite loop.
</p>
<p>
You can tune the frequency of your animation (default is 25Hz) using
<code>setAnimationInterval()</code>. The frame rate will then be fixed, provided that your
animation loop function is fast enough.
</p>
<h2>animation.h</h2>
<pre>
<span class="dir">#include <QGLViewer/qglviewer.h>
</span>
<span class="key">class </span>Particle
{
<span class="key">public </span>:
Particle();
<span class="typ">void </span>init();
<span class="typ">void </span>draw();
<span class="typ">void </span>animate();
<span class="key">private </span>:
qglviewer::Vec speed_, pos_;
<span class="typ">int </span>age_, ageMax_;
};
<span class="key">class </span>Viewer : <span class="key">public </span>QGLViewer
{
<span class="key">protected </span>:
<span class="key">virtual </span><span class="typ">void </span>draw();
<span class="key">virtual </span><span class="typ">void </span>init();
<span class="key">virtual </span><span class="typ">void </span>animate();
<span class="key">virtual </span>QString helpString() <span class="typ">const</span>;
<span class="key">private</span>:
<span class="typ">int </span>nbPart_;
Particle* particle_;
};
</pre>
<h2>animation.cpp</h2>
<pre>
<span class="dir">#include </span><span class="dstr">"animation.h"</span><span class="dir">
</span><span class="dir">#include <math.h>
</span><span class="dir">#include <stdlib.h> </span><span class="com">// RAND_MAX
</span><span class="dir"></span>
<span class="key">using namespace </span>qglviewer;
<span class="key">using namespace </span>std;
<span class="com">/////////////////////// V i e w e r ///////////////////////
</span><span class="typ">void </span>Viewer::init()
{
restoreFromFile();
glDisable(GL_LIGHTING);
nbPart_ = <span class="num">2000</span>;
particle_ = <span class="key">new </span>Particle[nbPart_];
glPointSize(<span class="num">3.0</span>);
setDrawGrid();
help();
startAnimation();
}
<span class="typ">void </span>Viewer::draw()
{
glBegin(GL_POINTS);
<span class="key">for </span>(<span class="typ">int </span>i=<span class="num">0</span>; i<nbPart_; i++)
particle_[i].draw();
glEnd();
}
<span class="typ">void </span>Viewer::animate()
{
<span class="key">for </span>(<span class="typ">int </span>i=<span class="num">0</span>; i<nbPart_; i++)
particle_[i].animate();
}
QString Viewer::helpString() <span class="typ">const
</span>{
QString text(<span class="str">"<h2>A n i m a t i o n</h2>"</span>);
text += <span class="str">"Use the <i>animate()</i> function to implement the animation part of your "</span>;
text += <span class="str">"application. Once the animation is started, <i>animate()</i> and <i>draw()</i> "</span>;
text += <span class="str">"are called in an infinite loop, at a frequency that can be fixed.<br>"</span>;
text += <span class="str">"Press <b>Return</b> to start/stop the animation."</span>;
<span class="key">return </span>text;
}
<span class="com">/////////////////////// P a r t i c l e ///////////////////////////////
</span>
Particle::Particle()
{
init();
}
<span class="typ">void </span>Particle::animate()
{
speed_.z -= <span class="num">0.05</span>;
pos_ += <span class="num">0.1 </span>* speed_;
<span class="key">if </span>(pos_.z < <span class="num">0.0</span>)
{
speed_.z = <span class="num">-0.8</span>*speed_.z;
pos_.z = <span class="num">0.0</span>;
}
<span class="key">if </span>(++age_ == ageMax_)
init();
}
<span class="typ">void </span>Particle::draw()
{
glColor3f(age_/(<span class="typ">float</span>)ageMax_, age_/(<span class="typ">float</span>)ageMax_, <span class="num">1.0</span>);
glVertex3fv(pos_.address());
}
<span class="typ">void </span>Particle::init()
{
pos_ = Vec(<span class="num">0.0</span>, <span class="num">0.0</span>, <span class="num">0.0</span>);
<span class="typ">float </span>angle = <span class="num">2.0 </span>* M_PI * rand() / RAND_MAX;
<span class="typ">float </span>norm = <span class="num">0.04 </span>* rand() / RAND_MAX;
speed_ = Vec(norm*cos(angle), norm*sin(angle), rand() / <span class="key">static_cast</span><<span class="typ">float</span>>(RAND_MAX) );
age_ = <span class="num">0</span>;
ageMax_ = <span class="num">50 </span>+ <span class="key">static_cast</span><<span class="typ">int</span>>(<span class="num">100.0 </span>* rand() / RAND_MAX);
}
</pre>
<h2>main.cpp</h2>
<pre>
<span class="dir">#include </span><span class="dstr">"animation.h"</span><span class="dir">
</span><span class="dir">#include <qapplication.h>
</span>
<span class="typ">int </span>main(<span class="typ">int </span>argc, <span class="typ">char</span>** argv)
{
<span class="com">// Read command lines arguments.
</span> QApplication application(argc,argv);
<span class="com">// Instantiate the viewer.
</span> Viewer v;
<span class="com">// Make the viewer window visible on screen.
</span> v.show();
<span class="com">// Set the viewer as the application main widget.
</span> application.setMainWidget(&v);
<span class="com">// Run main loop.
</span> <span class="key">return </span>application.exec();
}</pre>
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<i>Last modified on Thursday, February 5, 2004.</i>
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