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<title>libQGLViewer spinningFrame example</title>
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<h1>The spinningFrame example</h1>
<center>
<img src="../images/spinningFrame.jpg" width="300" height="200" alt="spinningFrame"/>
</center>
<p>
Illustration of the <code>SpinningFrame</code> class.
</p>
<p>
A SpinningFrame is useful to animate Frames that have a rotation motion.
An optional <code>rotationCenter</code> can be provided to create excentered motions.
</p>
<h2>spinningFrame.h</h2>
<pre>
<span class="dir">#include <QGLViewer/qglviewer.h>
</span>
<span class="key">class </span>Engine
{
<span class="key">public </span>:
Engine();
<span class="typ">void </span>draw();
<span class="key">protected </span>:
<span class="com">// The axis spinning frame of the conrod
</span> qglviewer::SpinningFrame axisFrame_;
qglviewer::SpinningFrame conrodFrame_;
<span class="key">private</span>:
<span class="typ">void </span>drawCone(<span class="typ">const float </span>zMin,<span class="typ">const float </span>zMax, <span class="typ">const float </span>r1, <span class="typ">const float </span>r2, <span class="typ">const float </span>nbSub);
<span class="typ">void </span>drawCylinder(<span class="typ">const float </span>zMin,<span class="typ">const float </span>zMax, <span class="typ">const float </span>r1, <span class="typ">const float </span>r2, <span class="typ">const float </span>nbSub);
};
<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>QString helpString() <span class="typ">const</span>;
<span class="key">private </span>:
Engine engine;
};</pre>
<h2>spinningFrame.cpp</h2>
<pre>
<span class="dir">#include </span><span class="dstr">"spinningFrame.h"</span><span class="dir">
</span><span class="dir">#include <math.h>
</span>
<span class="key">using namespace </span>qglviewer;
<span class="key">using namespace </span>std;
<span class="com">/////////////////////// E n g i n e ///////////////////////////////
</span>
Engine::Engine()
{
<span class="com">// Rotation around the Z axis. 0.04 radians increment.
</span> axisFrame_.setSpinningQuaternion(Quaternion(Vec(<span class="num">0</span>,<span class="num">0</span>,<span class="num">1</span>), <span class="num">0.04</span>));
<span class="com">// Same as axisFrame_, but with a rotationCenter
</span> conrodFrame_.setSpinningQuaternion(axisFrame_.spinningQuaternion());
<span class="com">// Default rotation center is the world origin. Kept unchanged.
</span> conrodFrame_.setRotateAroundCenter();
<span class="com">// The conrodFrame_ position is excentered to define the rotation radius.
</span> conrodFrame_.setPosition(Vec(<span class="num">0.4</span>, <span class="num">0.0</span>, <span class="num">0.0</span>));
<span class="com">// As the two spinningFrame are synchronized, there is not need to connect the two spinned()
</span> <span class="com">// signals to the updateGL() slot. We connect the axisFrame_ spinned signal only.
</span> QGLViewer::connectSignalToAllViewers(&axisFrame_, SIGNAL(spinned()));
<span class="com">// Default update interval is 40 milliseconds.
</span> axisFrame_.startSpinning();
conrodFrame_.startSpinning();
}
<span class="typ">void </span>Engine::draw()
{
<span class="com">// axisFrame_
</span> glColor3f(.<span class="num">6</span>, .<span class="num">4</span>, .<span class="num">4</span>);
glPushMatrix();
glMultMatrixd(axisFrame_.matrix());
drawCylinder(<span class="num">-0.3</span>, <span class="num">0.1</span>, <span class="num">0.1</span>, <span class="num">0.1</span>, <span class="num">50</span>);
glRotatef(<span class="num">90</span>, <span class="num">0.0</span>, <span class="num">1.0</span>, <span class="num">0.0</span>);
drawCone(<span class="num">0</span>, <span class="num">0.4</span>, <span class="num">0.1</span>, <span class="num">0.05</span>, <span class="num">50</span>);
glPopMatrix();
<span class="com">// conrodFrame_
</span> glColor3f(.<span class="num">4</span>, .<span class="num">6</span>, .<span class="num">4</span>);
glPushMatrix();
glMultMatrixd(conrodFrame_.matrix());
drawCylinder(<span class="num">-0.1</span>, <span class="num">0.4</span>, <span class="num">0.05</span>, <span class="num">0.05</span>, <span class="num">50</span>);
drawCylinder(<span class="num">0.1</span>, <span class="num">0.3</span>, <span class="num">0.1</span>, <span class="num">0.1</span>, <span class="num">50</span>);
glPopMatrix();
<span class="com">// Other parts
</span> glColor3f(.<span class="num">8</span>, .<span class="num">8</span>, .<span class="num">8</span>);
Vec p = conrodFrame_.position();
<span class="typ">const float </span>L = <span class="num">0.5</span>;
<span class="typ">float </span>angle = atan2(p.x, L);
glTranslatef(<span class="num">0.</span>, <span class="num">0.1 </span>+ p.y + L*cos(angle), .<span class="num">18</span>);
glRotatef(<span class="num">-90</span>, <span class="num">1.0</span>, <span class="num">0.0</span>, <span class="num">0.0</span>);
drawCylinder(<span class="num">0.0</span>, <span class="num">0.3</span>, <span class="num">0.15</span>, <span class="num">0.15</span>, <span class="num">50</span>);
glRotatef(<span class="num">180</span>+<span class="num">180</span>*angle/M_PI, <span class="num">0.0</span>,<span class="num">-1.0</span>,<span class="num">0.0</span>);
drawCone(<span class="num">0.0</span>, <span class="num">1.1</span>*L, <span class="num">0.04</span>, <span class="num">0.04</span>, <span class="num">50</span>);
}
<span class="com">// Draws a closed cylinder using drawCone()
</span><span class="typ">void </span>Engine::drawCylinder(<span class="typ">const float </span>zMin,<span class="typ">const float </span>zMax, <span class="typ">const float </span>r1, <span class="typ">const float </span>r2, <span class="typ">const float </span>nbSub)
{
<span class="typ">float </span>cap = <span class="num">0.05 </span>* (zMax - zMin);
drawCone(zMin-cap, zMin, <span class="num">0.0</span>, r1, nbSub);
drawCone(zMin, zMax, r1, r2, nbSub);
drawCone(zMax, zMax+cap, r2, <span class="num">0.0</span>, nbSub);
}
<span class="com">// Draws a truncated cone aligned with the Z axis.
</span><span class="typ">void </span>Engine::drawCone(<span class="typ">const float </span>zMin,<span class="typ">const float </span>zMax, <span class="typ">const float </span>r1, <span class="typ">const float </span>r2, <span class="typ">const float </span>nbSub)
{
<span class="typ">float </span>angle,c,s;
Vec normal, p1, p2;
glBegin(GL_QUAD_STRIP);
<span class="key">for </span>(<span class="typ">unsigned short </span>i=<span class="num">0</span>; i<=nbSub; ++i)
{
angle = <span class="num">2.0 </span>* M_PI * i / nbSub;
c = cos(angle);
s = sin(angle);
p1 = Vec(r1*c, r1*s, zMin);
p2 = Vec(r2*c, r2*s, zMax);
normal = cross(Vec(-s,c,<span class="num">0.0</span>) , (p2-p1));
normal.normalize();
glNormal3fv(normal.address());
glVertex3fv(p1.address());
glVertex3fv(p2.address());
}
glEnd();
}
<span class="com">/////////////////////// V i e w e r ///////////////////////
</span><span class="typ">void </span>Viewer::init()
{
restoreFromFile();
camera()->lookAt(<span class="num">0.0</span>, <span class="num">0.5</span>, <span class="num">0.0</span>);
help();
}
<span class="typ">void </span>Viewer::draw()
{
engine.draw();
}
QString Viewer::helpString() <span class="typ">const
</span>{
QString text(<span class="str">"<h2>S p i n n i n g F r a m e</h2>"</span>);
text += <span class="str">"The main axis is animated using a <i>SpinningFrame</i> (red). "</span>;
text += <span class="str">"An other <i>SpinningFrame</i> is used for the conrod (green), "</span>;
text += <span class="str">"but a rotation center is defined, creating this circular motion. "</span>;
text += <span class="str">"<i>SpinningFrame</i> are convenient to animate rotating scene objects."</span>;
<span class="key">return </span>text;
}</pre>
<h2>main.cpp</h2>
<pre>
<span class="dir">#include </span><span class="dstr">"spinningFrame.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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