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<h1>Constraint Class Reference</h1>A base class for <a class="el" href="classqglviewer_1_1Frame.html">Frame</a> constraints.
<a href="#_details">More...</a>
<p>
Inherited by <a class="el" href="classqglviewer_1_1AxisPlaneConstraint.html">AxisPlaneConstraint</a>, and <a class="el" href="classqglviewer_1_1TriangleSetConstraint.html">TriangleSetConstraint</a>.
<p>
<a href="classqglviewer_1_1Constraint-members.html">List of all members.</a><table border=0 cellpadding=0 cellspacing=0>
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<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#a0">~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#a1">constrainTranslation</a> (<a class="el" href="classqglviewer_1_1Vec.html">Vec</a> &, <a class="el" href="classqglviewer_1_1Frame.html">Frame</a> *const)</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#a2">constrainRotation</a> (<a class="el" href="classqglviewer_1_1Quaternion.html">Quaternion</a> &, <a class="el" href="classqglviewer_1_1Frame.html">Frame</a> *const)</td></tr>
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<hr><a name="_details"></a><h2>Detailed Description</h2>
A base class for <a class="el" href="classqglviewer_1_1Frame.html">Frame</a> constraints.
<p>
The different constraints that can be applied to a <a class="el" href="classqglviewer_1_1Frame.html">Frame</a> to limit its motion must all derive from this class. A frame can have its constrain defined with <a class="el" href="classqglviewer_1_1Frame.html#z45_1">Frame::setConstraint()</a>.<p>
<a class="el" href="classqglviewer_1_1Constraint.html#a1">constrainTranslation()</a> and <a class="el" href="classqglviewer_1_1Constraint.html#a2">constrainRotation()</a> can be overloaded to specify the constraint behavior. They take the desired displacement (translation or rotation) and the applied frame as parameters. The translation (resp. rotation) is then modified according to the constraint.<p>
The <a class="el" href="classqglviewer_1_1Frame.html#z39_0">Frame::translate()</a> and <a class="el" href="classqglviewer_1_1Frame.html#z39_5">Frame::rotate()</a> functions filter their input with the current <a class="el" href="classqglviewer_1_1Frame.html">Frame</a> constraint (if any): <div class="fragment"><pre> Frame::translate(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>
Default behavior (<a class="el" href="classqglviewer_1_1Constraint.html">Constraint</a> base class) implements no constraint : <a class="el" href="classqglviewer_1_1Constraint.html#a1">constrainTranslation()</a> and <a class="el" href="classqglviewer_1_1Constraint.html#a2">constrainRotation()</a> are identity functions.<p>
Try the <a href="../examples/constrainedFrame.html">constrainedFrame</a> and <a href="../examples/constrainedCamera.html">constrainedCamera</a> examples for an illustration.<p>
<h3>Implemented constraints</h3>
<p>
Classical constraints are provided for convenience : see the <a class="el" href="classqglviewer_1_1LocalConstraint.html">LocalConstraint</a>, <a class="el" href="classqglviewer_1_1WorldConstraint.html">WorldConstraint</a> and <a class="el" href="classqglviewer_1_1CameraConstraint.html">CameraConstraint</a> classes for axial and plane constraints. The <a class="el" href="classqglviewer_1_1TriangleSetConstraint.html">TriangleSetConstraint</a> is very useful for walk through applications, in order to force the camera to remain on a given path.<p>
<h3>Definig new constraints</h3>
<p>
The implementation of a new <a class="el" href="classqglviewer_1_1Constraint.html">Constraint</a> class simply consists in overloading the filtering functions: <div class="fragment"><pre> <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#a1">constrainTranslation</a>(Vec& t, Frame * <span class="keyword">const</span> fr)
{
<span class="comment">// The frame cannot have a negative z world coordinate.</span>
<span class="keywordflow">if</span> (fr->position().z + t.z < 0.0) <span class="comment">// new fr z coordinate</span>
t.z = fr->position().z; <span class="comment">// t.z is clamped</span>
}
};
myFrame->setConstraint(<span class="keyword">new</span> myConstraint());
</pre></div><p>
<h3>Combining constraints</h3>
<p>
Combining constraints can easily be achieved by creating a new class that will apply the different constraint filters: <div class="fragment"><pre> myConstraint::constrainTranslation(Vec& v, Frame* <span class="keyword">const</span> fr)
{
const1->constrainTranslation(v, fr);
const2->constrainTranslation(v, fr);
<span class="comment">// and so on, with possible branches, tests, loops...</span>
}
</pre></div>Much more complex constraint composition classes can be created in the same way.<p>
<dl compact><dt><b>Attention:</b></dt><dd><a class="el" href="classqglviewer_1_1Frame.html#z37_0">Frame::setTranslation()</a>, <a class="el" href="classqglviewer_1_1Frame.html#z37_3">Frame::setRotation()</a> and similar functions will actually <em>set</em> the frame position and orientation, without taking the constraint into consideration. Use the <em>WithConstraint</em> versions of these functions to enforce the constraint. </dd></dl>
<p>
<hr><h2>Constructor & Destructor Documentation</h2>
<a name="a0" doxytag="qglviewer::Constraint::~Constraint"></a><p>
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<td class="md" nowrap valign="top"> virtual ~<a class="el" href="classqglviewer_1_1Constraint.html">Constraint</a> </td>
<td class="md" valign="top">( </td>
<td class="mdname1" valign="top" nowrap> </td>
<td class="md" valign="top"> ) </td>
<td class="md" nowrap><code> [inline, virtual]</code></td>
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Virtual empty destructor. </td>
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<hr><h2>Member Function Documentation</h2>
<a name="a2" doxytag="qglviewer::Constraint::constrainRotation"></a><p>
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<td class="md" nowrap valign="top"> virtual void constrainRotation </td>
<td class="md" valign="top">( </td>
<td class="md" nowrap valign="top"><a class="el" href="classqglviewer_1_1Quaternion.html">Quaternion</a> & </td>
<td class="mdname" nowrap>, </td>
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<td class="md" nowrap><a class="el" href="classqglviewer_1_1Frame.html">Frame</a> * </td>
<td class="mdname" nowrap> <em>const</em></td>
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<td class="md">) </td>
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<p>
Default un-constrained rotation function. Desired rotation is expressed in <em>local</em> frame coordinate system.<p>
Overload this function in your own <a class="el" href="classqglviewer_1_1Constraint.html">Constraint</a> class to define a new rotational constraint. The frame which is applied a constrained rotation is given as a parameter. It is not defined <code>const</code>, but you should refrain from directly changing its value in the constraint.
<p>
Reimplemented in <a class="el" href="classqglviewer_1_1AxisPlaneConstraint.html#z31_0">AxisPlaneConstraint</a>, <a class="el" href="classqglviewer_1_1LocalConstraint.html#a2">LocalConstraint</a>, <a class="el" href="classqglviewer_1_1WorldConstraint.html#a2">WorldConstraint</a>, and <a class="el" href="classqglviewer_1_1CameraConstraint.html#a3">CameraConstraint</a>. </td>
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<a name="a1" doxytag="qglviewer::Constraint::constrainTranslation"></a><p>
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<td class="md" nowrap valign="top"> virtual void constrainTranslation </td>
<td class="md" valign="top">( </td>
<td class="md" nowrap valign="top"><a class="el" href="classqglviewer_1_1Vec.html">Vec</a> & </td>
<td class="mdname" nowrap>, </td>
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<td></td>
<td class="md" nowrap><a class="el" href="classqglviewer_1_1Frame.html">Frame</a> * </td>
<td class="mdname" nowrap> <em>const</em></td>
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<td class="md">) </td>
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Default un-constrained translation function. Desired translation is expressed in <em>local</em> frame coordinate system.<p>
Overload this function in your own <a class="el" href="classqglviewer_1_1Constraint.html">Constraint</a> class to define a new translation constraint. The frame which is applied a constrained translation is given as a parameter. It is not defined <code>const</code>, but you should refrain from directly changing its value in the constraint.
<p>
Reimplemented in <a class="el" href="classqglviewer_1_1AxisPlaneConstraint.html#z29_0">AxisPlaneConstraint</a>, <a class="el" href="classqglviewer_1_1LocalConstraint.html#a1">LocalConstraint</a>, <a class="el" href="classqglviewer_1_1WorldConstraint.html#a1">WorldConstraint</a>, <a class="el" href="classqglviewer_1_1CameraConstraint.html#a2">CameraConstraint</a>, and <a class="el" href="classqglviewer_1_1TriangleSetConstraint.html#a2">TriangleSetConstraint</a>. </td>
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