<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>libQGLViewer screenCoordSystem example</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<link href="../qglviewer.css" rel="stylesheet" type="text/css" />
<link rel="shortcut icon" href="../images/qglviewer.ico" type="image/x-icon" />
<link rel="icon" href="../images/qglviewer.icon.png" type="image/png" />
</head>
<body>
<table class="banner">
<tr>
<td align="center"><a href="../index.html"><b>Home</b></a></td>
<td align="center"><a href="../refManual/hierarchy.html"><b>Documentation</b></a></td>
<td align="center"><a href="../download.html"><b>Download</b></a></td>
<td align="center" class="qindexHL"><a href="index.html"><b>Screenshots</b></a></td>
<td align="center"><a href="../developer.html"><b>Developer</b></a></td>
</tr>
</table>
<h1>The screenCoordSystem example</h1>
<center>
<img src="../images/screenCoordSystem.jpg" width="300" height="200" alt="screenCoordSystem"/>
</center>
<p>
A saucers control viewer that illustrates the screen coordinate system feature.
</p>
<p>
Use <code>startScreenCoordinatesSystem()</code> and <code>stopScreenCoordinatesSystem()</code> to
set this mode. Once this mode has been activated in <code>draw()</code>, the X,Y coordinates
correspond to the pixel units (origin in the lower left corner). Combined with the
<code>camera()->projectedCoordinatesOf()</code>, this feature enable the mix of 2D and 3D drawing.
</p>
<p>
In this example, the arrows that designate the saucers seem to be attached to the object.
</p>
<h2>screenCoordSystem.h</h2>
<pre>
<span class="dir">#include <QGLViewer/qglviewer.h>
</span>
<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>init();
<span class="key">virtual </span><span class="typ">void </span>draw();
<span class="key">virtual </span>QString helpString() <span class="typ">const</span>;
<span class="key">private </span>:
<span class="typ">void </span>drawSaucer() <span class="typ">const</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</span>;
<span class="typ">static const int </span>nbSaucers = <span class="num">10</span>;
qglviewer::Frame saucerPos[nbSaucers];
qglviewer::Vec saucerColor[nbSaucers];
};</pre>
<h2>screenCoordSystem.cpp</h2>
<pre>
<span class="dir">#include </span><span class="dstr">"screenCoordSystem.h"</span><span class="dir">
</span><span class="dir">#include <stdio.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="typ">void </span>Viewer::init()
{
<span class="key">for </span>(<span class="typ">int </span>i=<span class="num">0</span>; i<nbSaucers; i++)
{
Vec pos;
pos.x = rand() / <span class="key">static_cast</span><<span class="typ">float</span>>(RAND_MAX) <span class="num">- 0.5</span>;
pos.y = rand() / <span class="key">static_cast</span><<span class="typ">float</span>>(RAND_MAX) <span class="num">- 0.5</span>;
pos.z = rand() / <span class="key">static_cast</span><<span class="typ">float</span>>(RAND_MAX) <span class="num">- 0.5</span>;
Quaternion ori(Vec(<span class="key">static_cast</span><<span class="typ">float</span>>(rand()) / RAND_MAX,
<span class="key">static_cast</span><<span class="typ">float</span>>(rand()) / RAND_MAX,
<span class="key">static_cast</span><<span class="typ">float</span>>(rand()) / RAND_MAX),
rand() / <span class="key">static_cast</span><<span class="typ">float</span>>(RAND_MAX) * M_PI);
saucerPos[i].setPosition(pos);
saucerPos[i].setOrientation(ori);
saucerColor[i].x = rand() / <span class="key">static_cast</span><<span class="typ">float</span>>(RAND_MAX);
saucerColor[i].y = rand() / <span class="key">static_cast</span><<span class="typ">float</span>>(RAND_MAX);
saucerColor[i].z = rand() / <span class="key">static_cast</span><<span class="typ">float</span>>(RAND_MAX);
}
restoreFromFile();
help();
}
QString Viewer::helpString() <span class="typ">const
</span>{
QString text(<span class="str">"<h2>S c r e e n C o o r d S y s t e m</h2>"</span>);
text += <span class="str">"This example illustrates the <i>startScreenCoordinatesSystem()</i> function "</span>;
text += <span class="str">"which enables a GL drawing directly into the screen coordinate system.<br>"</span>;
text += <span class="str">"The arrows are drawned using this method. The screen projection coordinates "</span>;
text += <span class="str">"of the objects is determined using <i>camera()->projectedCoordinatesOf()</i>, "</span>;
text += <span class="str">"thus <i>attaching</i> the 2D arrow to a 3D object"</span>;
<span class="key">return </span>text;
}
<span class="typ">void </span>Viewer::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
</span>{
<span class="typ">static const float </span>nbSub = <span class="num">32</span>;
<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="typ">void </span>Viewer::drawSaucer() <span class="typ">const
</span>{
drawCone(<span class="num">-0.014</span>, <span class="num">-0.01</span>, <span class="num">0.015</span>, <span class="num">0.03</span>);
drawCone(<span class="num">-0.01</span>, <span class="num">0.0</span>, <span class="num">0.03</span>, <span class="num">0.04</span>);
drawCone(<span class="num">0.0</span>, <span class="num">0.02</span>, <span class="num">0.05</span>, <span class="num">0.03</span>);
drawCone(<span class="num">0.02</span>, <span class="num">0.023</span>, <span class="num">0.03</span>, <span class="num">0.0</span>);
}
<span class="typ">void </span>Viewer::draw()
{
<span class="com">// Draw 3D flying saucers
</span> <span class="key">for </span>(<span class="typ">int </span>i=<span class="num">0</span>; i<nbSaucers; i++)
{
glPushMatrix();
glMultMatrixd(saucerPos[i].matrix());
glColor3fv(saucerColor[i].address());
drawSaucer();
glPopMatrix();
}
<span class="com">// Compute projected coordinates
</span> <span class="typ">int </span>projX[nbSaucers];
<span class="typ">int </span>projY[nbSaucers];
<span class="key">for </span>(<span class="typ">int </span>i=<span class="num">0</span>; i<nbSaucers; i++)
{
Vec projectedPos = camera()->projectedCoordinatesOf(saucerPos[i].position());
projX[i] = (<span class="typ">int</span>)(projectedPos.x);
projY[i] = (<span class="typ">int</span>)(projectedPos.y);
}
<span class="com">// Draw the arrows
</span> glColor3fv(foregroundColor().address());
startScreenCoordinatesSystem();
<span class="key">for </span>(<span class="typ">int </span>i=<span class="num">0</span>; i<nbSaucers; i++)
{
glBegin(GL_LINE_LOOP);
glVertex2i(projX[i]<span class="num">-50</span>, projY[i]);
glVertex2i(projX[i]<span class="num">-20</span>, projY[i]<span class="num">-4</span>);
glVertex2i(projX[i]<span class="num">-15</span>, projY[i]);
glVertex2i(projX[i]<span class="num">-20</span>, projY[i]+<span class="num">4</span>);
glEnd();
}
stopScreenCoordinatesSystem();
<span class="com">// Draw text id
</span> <span class="key">for </span>(<span class="typ">int </span>i=<span class="num">0</span>; i<nbSaucers; i++)
drawText(projX[i]<span class="num">-60</span>, projY[i]+<span class="num">4</span>, QString::number(i));
}
</pre>
<h2>main.cpp</h2>
<pre>
<span class="dir">#include </span><span class="dstr">"screenCoordSystem.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, show it on screen.
</span> Viewer viewer;
viewer.show();
<span class="com">// Set the viewer as the application main widget.
</span> application.setMainWidget(&viewer);
<span class="com">// Run main loop.
</span> <span class="key">return </span>application.exec();
}</pre>
<p>
<a href="index.html">Go back</a> to the examples main page
</p>
<p>
<a href="http://validator.w3.org/check/referer"><img src="../images/xhtml.png" alt="Valid XHTML 1.0!" height="31" width="88" border="0"/></a>
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img src="../images/css.png" width="88" height="31" alt="Valid CSS!" border="0"/></a>
<i>Last modified on Thursday, February 5, 2004.</i>
</p>
</body>
</html>
