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<h1>Constraint Class Reference</h1><!-- doxytag: class="qglviewer::Constraint" -->An interface class for <a class="el" href="classqglviewer_1_1Frame.html" title="The Frame class represents a coordinate system, defined by a position and an orientation...">Frame</a> constraints.
<a href="#_details">More...</a>
<p>
Inherited by <a class="el" href="classqglviewer_1_1AxisPlaneConstraint.html">AxisPlaneConstraint</a>.
<p>
<p>
<a href="classqglviewer_1_1Constraint-members.html">List of all members.</a><table border="0" cellpadding="0" cellspacing="0">
<tr><td></td></tr>
<tr><td colspan="2"><br><h2>Public Member Functions</h2></td></tr>
<tr><td class="memItemLeft" nowrap align="right" valign="top">virtual </td><td class="memItemRight" valign="bottom"><a class="el" href="classqglviewer_1_1Constraint.html#65f2b59f5bc1435bf439482d885b0c0a">~Constraint</a> ()</td></tr>
<tr><td class="memItemLeft" nowrap align="right" valign="top">virtual void </td><td class="memItemRight" valign="bottom"><a class="el" href="classqglviewer_1_1Constraint.html#b7d724965c6765209f47c1abe7f7b7b4">constrainTranslation</a> (<a class="el" href="classqglviewer_1_1Vec.html">Vec</a> &translation, <a class="el" href="classqglviewer_1_1Frame.html">Frame</a> *const frame)</td></tr>
<tr><td class="memItemLeft" nowrap align="right" valign="top">virtual void </td><td class="memItemRight" valign="bottom"><a class="el" href="classqglviewer_1_1Constraint.html#5de5f38e75b58476b7926171dba4b31b">constrainRotation</a> (<a class="el" href="classqglviewer_1_1Quaternion.html">Quaternion</a> &rotation, <a class="el" href="classqglviewer_1_1Frame.html">Frame</a> *const frame)</td></tr>
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<hr><a name="_details"></a><h2>Detailed Description</h2>
An interface class for <a class="el" href="classqglviewer_1_1Frame.html" title="The Frame class represents a coordinate system, defined by a position and an orientation...">Frame</a> constraints.
<p>
This class defines the interface for the Constraints that can be applied to a <a class="el" href="classqglviewer_1_1Frame.html" title="The Frame class represents a coordinate system, defined by a position and an orientation...">Frame</a> to limit its motion. Use <a class="el" href="classqglviewer_1_1Frame.html#dffa44cd173714b29f2441848a39c224">Frame::setConstraint()</a> to associate a <a class="el" href="classqglviewer_1_1Constraint.html" title="An interface class for Frame constraints.">Constraint</a> to a <a class="el" href="classqglviewer_1_1Frame.html" title="The Frame class represents a coordinate system, defined by a position and an orientation...">Frame</a> (default is a <code>NULL</code> <a class="el" href="classqglviewer_1_1Frame.html#0974dfe336ed84a20adb8c6cdf8dedd9">Frame::constraint()</a>).<p>
<h3>How does it work ?</h3>
<p>
The <a class="el" href="classqglviewer_1_1Constraint.html" title="An interface class for Frame constraints.">Constraint</a> acts as a filter on the translation and rotation <a class="el" href="classqglviewer_1_1Frame.html" title="The Frame class represents a coordinate system, defined by a position and an orientation...">Frame</a> increments. <a class="el" href="classqglviewer_1_1Constraint.html#b7d724965c6765209f47c1abe7f7b7b4">constrainTranslation()</a> and <a class="el" href="classqglviewer_1_1Constraint.html#5de5f38e75b58476b7926171dba4b31b">constrainRotation()</a> should be overloaded to specify the constraint behavior: the desired displacement is given as a parameter that can optionally be modified.<p>
Here is how the <a class="el" href="classqglviewer_1_1Frame.html#4cb0cf5ff79e1acf0755befdaceb6f4a">Frame::translate()</a> and <a class="el" href="classqglviewer_1_1Frame.html#38dffd6ee0ad7e395b49082b2b94de33">Frame::rotate()</a> methods use the <a class="el" href="classqglviewer_1_1Constraint.html" title="An interface class for Frame constraints.">Constraint</a>: <div class="fragment"><pre class="fragment"> <a class="code" href="classqglviewer_1_1Frame.html#4cb0cf5ff79e1acf0755befdaceb6f4a">Frame::translate</a>(Vec& T)
{
<span class="keywordflow">if</span> (constraint())
constraint()->constrainTranslation(T, <span class="keyword">this</span>);
t += T;
}
Frame::rotate(Quaternion& Q)
{
<span class="keywordflow">if</span> (constraint())
constraint()->constrainRotation(Q, <span class="keyword">this</span>);
q *= Q;
}
</pre></div><p>
The default behavior of <a class="el" href="classqglviewer_1_1Constraint.html#b7d724965c6765209f47c1abe7f7b7b4">constrainTranslation()</a> and <a class="el" href="classqglviewer_1_1Constraint.html#5de5f38e75b58476b7926171dba4b31b">constrainRotation()</a> is empty (meaning no filtering).<p>
The <a class="el" href="classqglviewer_1_1Frame.html" title="The Frame class represents a coordinate system, defined by a position and an orientation...">Frame</a> which uses the <a class="el" href="classqglviewer_1_1Constraint.html" title="An interface class for Frame constraints.">Constraint</a> is passed as a parameter to the <a class="el" href="classqglviewer_1_1Constraint.html#b7d724965c6765209f47c1abe7f7b7b4">constrainTranslation()</a> and <a class="el" href="classqglviewer_1_1Constraint.html#5de5f38e75b58476b7926171dba4b31b">constrainRotation()</a> methods, so that they can have access to its current state (mainly <a class="el" href="classqglviewer_1_1Frame.html#bc38a05a597e07c9ff525122682adc50">Frame::position()</a> and <a class="el" href="classqglviewer_1_1Frame.html#691af39b54669fad8b4e73599de22094">Frame::orientation()</a>). It is not <code>const</code> for versatility reasons, but directly modifying it should be avoided.<p>
<dl class="attention" compact><dt><b>Attention:</b></dt><dd><a class="el" href="classqglviewer_1_1Frame.html#e5495cd791858225ba7c85ce39329704">Frame::setTranslation()</a>, <a class="el" href="classqglviewer_1_1Frame.html#857aacdb88a574ec4a363335f6152a1e">Frame::setRotation()</a> and similar methods will actually indeed set the frame position and orientation, without taking the constraint into account. Use the <em>WithConstraint</em> versions of these methods to enforce the <a class="el" href="classqglviewer_1_1Constraint.html" title="An interface class for Frame constraints.">Constraint</a>.</dd></dl>
<h3>Implemented Constraints</h3>
<p>
Classical axial and plane Constraints are provided for convenience: see the <a class="el" href="classqglviewer_1_1LocalConstraint.html" title="An AxisPlaneConstraint defined in the Frame local coordinate system.">LocalConstraint</a>, <a class="el" href="classqglviewer_1_1WorldConstraint.html" title="An AxisPlaneConstraint defined in the world coordinate system.">WorldConstraint</a> and <a class="el" href="classqglviewer_1_1CameraConstraint.html" title="An AxisPlaneConstraint defined in the camera coordinate system.">CameraConstraint</a> classes' documentations.<p>
Try the <a href="../examples/constrainedFrame.html">constrainedFrame</a> and <a href="../examples/constrainedCamera.html">constrainedCamera</a> examples for an illustration.<p>
<h3>Creating new Constraints</h3>
<p>
The implementation of a new <a class="el" href="classqglviewer_1_1Constraint.html" title="An interface class for Frame constraints.">Constraint</a> class simply consists in overloading the filtering methods: <div class="fragment"><pre class="fragment"> <span class="comment">// This Constraint enforces that the Frame cannot have a negative z world coordinate.</span>
<span class="keyword">class </span>myConstraint : <span class="keyword">public</span> Constraint
{
<span class="keyword">public</span>:
<span class="keyword">virtual</span> <span class="keywordtype">void</span> <a class="code" href="classqglviewer_1_1Constraint.html#b7d724965c6765209f47c1abe7f7b7b4">constrainTranslation</a>(Vec& t, Frame * <span class="keyword">const</span> fr)
{
<span class="comment">// Express t in the world coordinate system.</span>
<span class="keyword">const</span> Vec tWorld = fr->inverseTransformOf(t);
<span class="keywordflow">if</span> (fr->position().z + tWorld.z < 0.0) <span class="comment">// check the new fr z coordinate</span>
t.z = fr->transformOf(-fr->position().z); <span class="comment">// t.z is clamped so that next z position is 0.0</span>
}
};
</pre></div><p>
Note that the translation (resp. rotation) parameter passed to <a class="el" href="classqglviewer_1_1Constraint.html#b7d724965c6765209f47c1abe7f7b7b4">constrainTranslation()</a> (resp. <a class="el" href="classqglviewer_1_1Constraint.html#5de5f38e75b58476b7926171dba4b31b">constrainRotation()</a>) is expressed in the <em>local</em> <a class="el" href="classqglviewer_1_1Frame.html" title="The Frame class represents a coordinate system, defined by a position and an orientation...">Frame</a> coordinate system. Here, we use the <a class="el" href="classqglviewer_1_1Frame.html#05a3e18419f02427366a95b1e299f12e">Frame::transformOf()</a> and <a class="el" href="classqglviewer_1_1Frame.html#ba2c6c46c1825a81f09d22322b03d9b5">Frame::inverseTransformOf()</a> method to convert it to and from the world coordinate system.<p>
Combined constraints can easily be achieved by creating a new class that applies the different constraint filters: <div class="fragment"><pre class="fragment"> myConstraint::constrainTranslation(Vec& v, Frame* <span class="keyword">const</span> fr)
{
constraint1->constrainTranslation(v, fr);
constraint2->constrainTranslation(v, fr);
<span class="comment">// and so on, with possible branches, tests, loops...</span>
}
</pre></div> <hr><h2>Constructor & Destructor Documentation</h2>
<a class="anchor" name="65f2b59f5bc1435bf439482d885b0c0a"></a><!-- doxytag: member="qglviewer::Constraint::~Constraint" ref="65f2b59f5bc1435bf439482d885b0c0a" args="()" -->
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<td class="memname">virtual ~Constraint </td>
<td>(</td>
<td class="paramname"> </td>
<td> ) </td>
<td width="100%"><code> [virtual]</code></td>
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<p>
Virtual destructor. Empty.
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<hr><h2>Member Function Documentation</h2>
<a class="anchor" name="b7d724965c6765209f47c1abe7f7b7b4"></a><!-- doxytag: member="qglviewer::Constraint::constrainTranslation" ref="b7d724965c6765209f47c1abe7f7b7b4" args="(Vec &translation, Frame *const frame)" -->
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<td class="memname">virtual void constrainTranslation </td>
<td>(</td>
<td class="paramtype"><a class="el" href="classqglviewer_1_1Vec.html">Vec</a> & </td>
<td class="paramname"> <em>translation</em>, </td>
</tr>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="classqglviewer_1_1Frame.html">Frame</a> *const </td>
<td class="paramname"> <em>frame</em></td><td> </td>
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<td>)</td>
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<p>
Filters the translation applied to the <code>frame</code>. This default implementation is empty (no filtering).<p>
Overload this method in your own <a class="el" href="classqglviewer_1_1Constraint.html" title="An interface class for Frame constraints.">Constraint</a> class to define a new translation constraint. <code>frame</code> is the <a class="el" href="classqglviewer_1_1Frame.html" title="The Frame class represents a coordinate system, defined by a position and an orientation...">Frame</a> to which is applied the translation. It is not defined <code>const</code>, but you should refrain from directly changing its value in the constraint. Use its <a class="el" href="classqglviewer_1_1Frame.html#bc38a05a597e07c9ff525122682adc50">Frame::position()</a> and update the <code>translation</code> accordingly instead.<p>
<code>translation</code> is expressed in local frame coordinate system. Use <a class="el" href="classqglviewer_1_1Frame.html#ba2c6c46c1825a81f09d22322b03d9b5">Frame::inverseTransformOf()</a> to express it in the world coordinate system if needed.
<p>Reimplemented in <a class="el" href="classqglviewer_1_1AxisPlaneConstraint.html#b7d724965c6765209f47c1abe7f7b7b4">AxisPlaneConstraint</a>, <a class="el" href="classqglviewer_1_1LocalConstraint.html#dc695bfbc605b5631be663b28a4ea9f6">LocalConstraint</a>, <a class="el" href="classqglviewer_1_1WorldConstraint.html#dc695bfbc605b5631be663b28a4ea9f6">WorldConstraint</a>, and <a class="el" href="classqglviewer_1_1CameraConstraint.html#dc695bfbc605b5631be663b28a4ea9f6">CameraConstraint</a>.</p>
</div>
</div><p>
<a class="anchor" name="5de5f38e75b58476b7926171dba4b31b"></a><!-- doxytag: member="qglviewer::Constraint::constrainRotation" ref="5de5f38e75b58476b7926171dba4b31b" args="(Quaternion &rotation, Frame *const frame)" -->
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<td class="memname">virtual void constrainRotation </td>
<td>(</td>
<td class="paramtype"><a class="el" href="classqglviewer_1_1Quaternion.html">Quaternion</a> & </td>
<td class="paramname"> <em>rotation</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="classqglviewer_1_1Frame.html">Frame</a> *const </td>
<td class="paramname"> <em>frame</em></td><td> </td>
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<td></td>
<td>)</td>
<td></td><td></td><td width="100%"><code> [virtual]</code></td>
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<p>
Filters the rotation applied to the <code>frame</code>. This default implementation is empty (no filtering).<p>
Overload this method in your own <a class="el" href="classqglviewer_1_1Constraint.html" title="An interface class for Frame constraints.">Constraint</a> class to define a new rotation constraint. See <a class="el" href="classqglviewer_1_1Constraint.html#b7d724965c6765209f47c1abe7f7b7b4">constrainTranslation()</a> for details.<p>
Use <a class="el" href="classqglviewer_1_1Frame.html#ba2c6c46c1825a81f09d22322b03d9b5">Frame::inverseTransformOf()</a> on the <code>rotation</code> <a class="el" href="classqglviewer_1_1Quaternion.html#63f3f585fd25e9cb32700a26d54f8ee4">Quaternion::axis()</a> to express <code>rotation</code> in the world coordinate system if needed.
<p>Reimplemented in <a class="el" href="classqglviewer_1_1AxisPlaneConstraint.html#5de5f38e75b58476b7926171dba4b31b">AxisPlaneConstraint</a>, <a class="el" href="classqglviewer_1_1LocalConstraint.html#71c099a2c356f715f8bf34052875cd25">LocalConstraint</a>, <a class="el" href="classqglviewer_1_1WorldConstraint.html#71c099a2c356f715f8bf34052875cd25">WorldConstraint</a>, and <a class="el" href="classqglviewer_1_1CameraConstraint.html#71c099a2c356f715f8bf34052875cd25">CameraConstraint</a>.</p>
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