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<title>libQGLViewer frameTransform example</title>
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<h1>The frameTransform example</h1>
<center>
<img src="../images/frameTransform.jpg" width="330" height="228" alt="frameTransform"/>
</center>
<p>
Coordinate transformation between different Frames.
</p>
<p>
This example illustrates the camera and world coordinate systems relationship. The position of the
camera in the world coordinate system is printed from <code>camera()->position()</code>.
Symmetrically, the position of the world origin is given in the camera coordinate system by
<code>camera()->cameraCoordinatesOf(0,0,0)</code>.
</p>
<p>
Three sets of lines (red, green, blue) are drawn. They have different starting points, but common
end points, located on a circle in the XY plane.
</p>
<p>
All the red lines start from the camera position, and will hence always be aligned with the
viewing direction, making them invisible.
</p>
<p>
The green lines starting points' positions are determined from the camera coordinate system, using
<code>camera()->worldCoordinatesOf()</code>. As a result, these points will seem to be fixed on
the screen, even when the camera is moved
</p>
<p>
Finally, the blue lines are classically defined in the world coordinate system, and will move with
the camera.
</p>
<p>
Beautiful Moire pattern can be obtained with a proper rotation.
</p>
<h2>frameTransform.h</h2>
<!-- Generator: GNU source-highlight 2.4
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><b><font color="#000080">#include</font></b> <font color="#FF0000"><QGLViewer/qglviewer.h></font>
<b><font color="#0000FF">class</font></b> Viewer <font color="#990000">:</font> <b><font color="#0000FF">public</font></b> QGLViewer
<font color="#FF0000">{</font>
<b><font color="#0000FF">protected</font></b> <font color="#990000">:</font>
<b><font color="#0000FF">virtual</font></b> <font color="#009900">void</font> <b><font color="#000000">draw</font></b><font color="#990000">();</font>
<b><font color="#0000FF">virtual</font></b> <font color="#009900">void</font> <b><font color="#000000">init</font></b><font color="#990000">();</font>
<b><font color="#0000FF">virtual</font></b> QString <b><font color="#000000">helpString</font></b><font color="#990000">()</font> <b><font color="#0000FF">const</font></b><font color="#990000">;</font>
<font color="#FF0000">}</font><font color="#990000">;</font>
</tt></pre>
<h2>frameTransform.cpp</h2>
<!-- Generator: GNU source-highlight 2.4
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><b><font color="#000080">#include</font></b> <font color="#FF0000">"frameTransform.h"</font>
<b><font color="#0000FF">using</font></b> <b><font color="#0000FF">namespace</font></b> std<font color="#990000">;</font>
<b><font color="#0000FF">using</font></b> <b><font color="#0000FF">namespace</font></b> qglviewer<font color="#990000">;</font> <i><font color="#9A1900">// Vec</font></i>
<font color="#009900">void</font> Viewer<font color="#990000">::</font><b><font color="#000000">init</font></b><font color="#990000">()</font>
<font color="#FF0000">{</font>
<b><font color="#000000">restoreStateFromFile</font></b><font color="#990000">();</font>
<b><font color="#000000">setSceneRadius</font></b><font color="#990000">(</font><font color="#993399">1.5</font><font color="#990000">);</font>
<b><font color="#000000">showEntireScene</font></b><font color="#990000">();</font>
<b><font color="#000000">setAxisIsDrawn</font></b><font color="#990000">();</font>
<b><font color="#000000">glDisable</font></b><font color="#990000">(</font>GL_LIGHTING<font color="#990000">);</font>
<b><font color="#000000">help</font></b><font color="#990000">();</font>
<font color="#FF0000">}</font>
<font color="#009900">void</font> Viewer<font color="#990000">::</font><b><font color="#000000">draw</font></b><font color="#990000">()</font>
<font color="#FF0000">{</font>
<i><font color="#9A1900">// Draws line sets (red, green, blue) with different origins, but with a common</font></i>
<i><font color="#9A1900">// end point, located on a circle in the XY plane.</font></i>
<b><font color="#0000FF">const</font></b> <font color="#009900">float</font> nbLines <font color="#990000">=</font> <font color="#993399">50.0</font><font color="#990000">;</font>
<b><font color="#000000">glBegin</font></b><font color="#990000">(</font>GL_LINES<font color="#990000">);</font>
<b><font color="#0000FF">for</font></b> <font color="#990000">(</font><font color="#009900">float</font> i<font color="#990000">=</font><font color="#993399">0</font><font color="#990000">;</font> i<font color="#990000"><</font>nbLines<font color="#990000">;</font> <font color="#990000">++</font>i<font color="#990000">)</font>
<font color="#FF0000">{</font>
<font color="#009900">float</font> angle <font color="#990000">=</font> <font color="#993399">2.0</font><font color="#990000">*</font>M_PI<font color="#990000">*</font>i<font color="#990000">/</font>nbLines<font color="#990000">;</font>
<b><font color="#000000">glColor3f</font></b><font color="#990000">(</font><font color="#993399">0</font><font color="#990000">.</font>8f<font color="#990000">,</font> <font color="#993399">0</font><font color="#990000">.</font>2f<font color="#990000">,</font> <font color="#993399">0</font><font color="#990000">.</font>2f<font color="#990000">);</font>
<i><font color="#9A1900">// These lines will never be seen as they are always aligned with the viewing direction.</font></i>
<b><font color="#000000">glVertex3fv</font></b><font color="#990000">(</font><b><font color="#000000">camera</font></b><font color="#990000">()-></font><b><font color="#000000">position</font></b><font color="#990000">());</font>
<b><font color="#000000">glVertex3f </font></b><font color="#990000">(</font><b><font color="#000000">cos</font></b><font color="#990000">(</font>angle<font color="#990000">),</font> <b><font color="#000000">sin</font></b><font color="#990000">(</font>angle<font color="#990000">),</font> <font color="#993399">0.0</font><font color="#990000">);</font>
<b><font color="#000000">glColor3f</font></b><font color="#990000">(</font><font color="#993399">0</font><font color="#990000">.</font>2f<font color="#990000">,</font> <font color="#993399">0</font><font color="#990000">.</font>8f<font color="#990000">,</font> <font color="#993399">0</font><font color="#990000">.</font>2f<font color="#990000">);</font>
<i><font color="#9A1900">// World Coordinates are infered from the camera, and seem to be immobile in the screen.</font></i>
<b><font color="#000000">glVertex3fv</font></b><font color="#990000">(</font><b><font color="#000000">camera</font></b><font color="#990000">()-></font><b><font color="#000000">worldCoordinatesOf</font></b><font color="#990000">(</font><b><font color="#000000">Vec</font></b><font color="#990000">(.</font><font color="#993399">3</font><font color="#990000">*</font><b><font color="#000000">cos</font></b><font color="#990000">(</font>angle<font color="#990000">),</font> <font color="#990000">.</font><font color="#993399">3</font><font color="#990000">*</font><b><font color="#000000">sin</font></b><font color="#990000">(</font>angle<font color="#990000">),</font> <font color="#990000">-</font><font color="#993399">2.0</font><font color="#990000">)));</font>
<b><font color="#000000">glVertex3f </font></b><font color="#990000">(</font><b><font color="#000000">cos</font></b><font color="#990000">(</font>angle<font color="#990000">),</font> <b><font color="#000000">sin</font></b><font color="#990000">(</font>angle<font color="#990000">),</font> <font color="#993399">0.0</font><font color="#990000">);</font>
<b><font color="#000000">glColor3f</font></b><font color="#990000">(</font><font color="#993399">0</font><font color="#990000">.</font>2f<font color="#990000">,</font> <font color="#993399">0</font><font color="#990000">.</font>2f<font color="#990000">,</font> <font color="#993399">0</font><font color="#990000">.</font>8f<font color="#990000">);</font>
<i><font color="#9A1900">// These lines are defined in the world coordinate system and will move with the camera.</font></i>
<b><font color="#000000">glVertex3f</font></b><font color="#990000">(</font><font color="#993399">1.5</font><font color="#990000">*</font><b><font color="#000000">cos</font></b><font color="#990000">(</font>angle<font color="#990000">),</font> <font color="#993399">1.5</font><font color="#990000">*</font><b><font color="#000000">sin</font></b><font color="#990000">(</font>angle<font color="#990000">),</font> <font color="#990000">-</font><font color="#993399">1.0</font><font color="#990000">);</font>
<b><font color="#000000">glVertex3f</font></b><font color="#990000">(</font><b><font color="#000000">cos</font></b><font color="#990000">(</font>angle<font color="#990000">),</font> <b><font color="#000000">sin</font></b><font color="#990000">(</font>angle<font color="#990000">),</font> <font color="#993399">0.0</font><font color="#990000">);</font>
<font color="#FF0000">}</font>
<b><font color="#000000">glEnd</font></b><font color="#990000">();</font>
<i><font color="#9A1900">// Here, the camera position in world coord. system is camera()->position().</font></i>
<i><font color="#9A1900">// The world origin position in camera frame can be obtained from camera()->cameraCoordinatesOf(Vec(0.0, 0.0, 0.0))</font></i>
<font color="#FF0000">}</font>
QString Viewer<font color="#990000">::</font><b><font color="#000000">helpString</font></b><font color="#990000">()</font> <b><font color="#0000FF">const</font></b>
<font color="#FF0000">{</font>
QString <b><font color="#000000">text</font></b><font color="#990000">(</font><font color="#FF0000">"<h2>F r a m e T r a n s f o r m</h2>"</font><font color="#990000">);</font>
text <font color="#990000">+=</font> <font color="#FF0000">"This example illustrates how easy it is to switch between the camera and "</font><font color="#990000">;</font>
text <font color="#990000">+=</font> <font color="#FF0000">"the world coordinate systems using the <i>camera()->cameraCoordinatesOf()</i> "</font><font color="#990000">;</font>
text <font color="#990000">+=</font> <font color="#FF0000">"and <i>camera::worldCoordinatesOf()</i> functions.<br><br>"</font><font color="#990000">;</font>
text <font color="#990000">+=</font> <font color="#FF0000">"You can create your own hierarchy of local coordinates systems and each of "</font><font color="#990000">;</font>
text <font color="#990000">+=</font> <font color="#FF0000">"them can be manipulated with the mouse (see the <i>manipulatedFrame</i> and <i>luxo</i> examples). "</font><font color="#990000">;</font>
text <font color="#990000">+=</font> <font color="#FF0000">"Standard functions allow you to convert from any local frame to any other, "</font><font color="#990000">;</font>
text <font color="#990000">+=</font> <font color="#FF0000">"the world/camera conversion presented here simply being an illustration.<br><br>"</font><font color="#990000">;</font>
text <font color="#990000">+=</font> <font color="#FF0000">"See <i>examples/frameTransform.html</i> for an explanation of the meaning of these weird lines."</font><font color="#990000">;</font>
<b><font color="#0000FF">return</font></b> text<font color="#990000">;</font>
<font color="#FF0000">}</font>
</tt></pre>
<h2>main.cpp</h2>
<!-- Generator: GNU source-highlight 2.4
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><b><font color="#000080">#include</font></b> <font color="#FF0000">"frameTransform.h"</font>
<b><font color="#000080">#include</font></b> <font color="#FF0000"><qapplication.h></font>
<font color="#009900">int</font> <b><font color="#000000">main</font></b><font color="#990000">(</font><font color="#009900">int</font> argc<font color="#990000">,</font> <font color="#009900">char</font><font color="#990000">**</font> argv<font color="#990000">)</font>
<font color="#FF0000">{</font>
QApplication <b><font color="#000000">application</font></b><font color="#990000">(</font>argc<font color="#990000">,</font>argv<font color="#990000">);</font>
Viewer viewer<font color="#990000">;</font>
<b><font color="#000080">#if</font></b> QT_VERSION <font color="#990000"><</font> <font color="#993399">0x040000</font>
application<font color="#990000">.</font><b><font color="#000000">setMainWidget</font></b><font color="#990000">(&</font>viewer<font color="#990000">);</font>
<b><font color="#000080">#else</font></b>
viewer<font color="#990000">.</font><b><font color="#000000">setWindowTitle</font></b><font color="#990000">(</font><font color="#FF0000">"frameTransform"</font><font color="#990000">);</font>
<b><font color="#000080">#endif</font></b>
viewer<font color="#990000">.</font><b><font color="#000000">show</font></b><font color="#990000">();</font>
<b><font color="#0000FF">return</font></b> application<font color="#990000">.</font><b><font color="#000000">exec</font></b><font color="#990000">();</font>
<font color="#FF0000">}</font>
</tt></pre>
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<i>Last modified on Tuesday, September 30, 2008.</i>
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