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<h1>The simpleViewer example</h1>
<center>
<img src="../images/simpleViewer.jpg" width="330" height="228" alt="simpleViewer"/>
</center>
<p>
The simplest application example: 20 lines of code and yet all the power !
</p>
<p>
A Viewer class is derived from QGLViewer and its <code>draw()</code> function is overloaded to
specify the user defined OpenGL orders that describe the scene.
</p>
<p>
This is the first example you should try, as it explains some of the default keyboard shortcuts
and the mouse behavior of the viewer.
</p>
<p>
This example can be cut and pasted to start the development of a new application.
</p>
<h2>simpleViewer.h</h2>
<pre>
#include <QGLViewer/qglviewer.h>
class Viewer : public QGLViewer {
protected:
virtual void draw();
virtual void init();
virtual QString helpString() const;
};
</pre>
<h2>simpleViewer.cpp</h2>
<pre>
#include "simpleViewer.h"
using namespace std;
// Draws a spiral
void Viewer::draw() {
const float nbSteps = 200.0;
glBegin(GL_QUAD_STRIP);
for (int i = 0; i < nbSteps; ++i) {
const float ratio = i / nbSteps;
const float angle = 21.0 * ratio;
const float c = cos(angle);
const float s = sin(angle);
const float r1 = 1.0 - 0.8f * ratio;
const float r2 = 0.8f - 0.8f * ratio;
const float alt = ratio - 0.5f;
const float nor = 0.5f;
const float up = sqrt(1.0 - nor * nor);
glColor3f(1.0 - ratio, 0.2f, ratio);
glNormal3f(nor * c, up, nor * s);
glVertex3f(r1 * c, alt, r1 * s);
glVertex3f(r2 * c, alt + 0.05f, r2 * s);
}
glEnd();
}
void Viewer::init() {
// Restore previous viewer state.
restoreStateFromFile();
// Opens help window
help();
}
QString Viewer::helpString() const {
QString text("<h2>S i m p l e V i e w e r</h2>");
text += "Use the mouse to move the camera around the object. ";
text += "You can respectively revolve around, zoom and translate with the "
"three mouse buttons. ";
text += "Left and middle buttons pressed together rotate around the camera "
"view direction axis<br><br>";
text += "Pressing <b>Alt</b> and one of the function keys "
"(<b>F1</b>..<b>F12</b>) defines a camera keyFrame. ";
text += "Simply press the function key again to restore it. Several "
"keyFrames define a ";
text += "camera path. Paths are saved when you quit the application and "
"restored at next start.<br><br>";
text +=
"Press <b>F</b> to display the frame rate, <b>A</b> for the world axis, ";
text += "<b>Alt+Return</b> for full screen mode and <b>Control+S</b> to save "
"a snapshot. ";
text += "See the <b>Keyboard</b> tab in this window for a complete shortcut "
"list.<br><br>";
text += "Double clicks automates single click actions: A left button double "
"click aligns the closer axis with the camera (if close enough). ";
text += "A middle button double click fits the zoom of the camera and the "
"right button re-centers the scene.<br><br>";
text += "A left button double click while holding right button pressed "
"defines the camera <i>Revolve Around Point</i>. ";
text += "See the <b>Mouse</b> tab and the documentation web pages for "
"details.<br><br>";
text += "Press <b>Escape</b> to exit the viewer.";
return text;
}
</pre>
<h2>main.cpp</h2>
<pre>
#include "simpleViewer.h"
#include <qapplication.h>
int main(int argc, char **argv) {
// Read command lines arguments.
QApplication application(argc, argv);
// Instantiate the viewer.
Viewer viewer;
viewer.setWindowTitle("simpleViewer");
// Make the viewer window visible on screen.
viewer.show();
// Run main loop.
return application.exec();
}
</pre>
<p>
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