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<title>GEOS: geos::operation::geounion::CascadedPolygonUnion Class Reference</title>
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<li><a class="el" href="namespacegeos.html">geos</a> </li>
<li><a class="el" href="namespacegeos_1_1operation.html">operation</a> </li>
<li><b>geounion</b> </li>
<li><a class="el" href="classgeos_1_1operation_1_1geounion_1_1CascadedPolygonUnion.html">geos::operation::geounion::CascadedPolygonUnion</a> </li>
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<a href="#pub-methods">Public Member Functions</a> |
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<h1>geos::operation::geounion::CascadedPolygonUnion Class Reference</h1> </div>
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<p>Provides an efficient method of unioning a collection of <a class="el" href="">Polygonal</a> geometries. This algorithm is faster and likely more robust than the simple iterated approach of repeatedly unioning each polygon to a result geometry.
<a href="#_details">More...</a></p>
<p><code>#include <<a class="el" href="CascadedPolygonUnion_8h_source.html">CascadedPolygonUnion.h</a>></code></p>
<p><a href="classgeos_1_1operation_1_1geounion_1_1CascadedPolygonUnion-members.html">List of all members.</a></p>
<table class="memberdecls">
<tr><td colspan="2"><h2><a name="pub-methods"></a>
Public Member Functions</h2></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="classgeos_1_1operation_1_1geounion_1_1CascadedPolygonUnion.html#a056d0965591c58d015e1bc5b924a9999">CascadedPolygonUnion</a> (std::vector< <a class="el" href="classgeos_1_1geom_1_1Polygon.html">geom::Polygon</a> * > *polys)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="el" href="classgeos_1_1geom_1_1Geometry.html">geom::Geometry</a> * </td><td class="memItemRight" valign="bottom"><a class="el" href="classgeos_1_1operation_1_1geounion_1_1CascadedPolygonUnion.html#a85d370411643071a75f507b604412ce2">Union</a> ()</td></tr>
<tr><td colspan="2"><h2><a name="pub-static-methods"></a>
Static Public Member Functions</h2></td></tr>
<tr><td class="memItemLeft" align="right" valign="top">static <a class="el" href="classgeos_1_1geom_1_1Geometry.html">geom::Geometry</a> * </td><td class="memItemRight" valign="bottom"><a class="el" href="classgeos_1_1operation_1_1geounion_1_1CascadedPolygonUnion.html#a721608ec9629555af43648ddd32c19b8">Union</a> (std::vector< <a class="el" href="classgeos_1_1geom_1_1Polygon.html">geom::Polygon</a> * > *polys)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">static <a class="el" href="classgeos_1_1geom_1_1Geometry.html">geom::Geometry</a> * </td><td class="memItemRight" valign="bottom"><a class="el" href="classgeos_1_1operation_1_1geounion_1_1CascadedPolygonUnion.html#ab2137d4ee76db279ce43fa719c77cbf7">Union</a> (const <a class="el" href="classgeos_1_1geom_1_1MultiPolygon.html">geom::MultiPolygon</a> *polys)</td></tr>
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<hr/><a name="_details"></a><h2>Detailed Description</h2>
<p>Provides an efficient method of unioning a collection of <a class="el" href="">Polygonal</a> geometries. This algorithm is faster and likely more robust than the simple iterated approach of repeatedly unioning each polygon to a result geometry. </p>
<p>The <code>buffer(0)</code> trick is sometimes faster, but can be less robust and can sometimes take an exceptionally long time to complete. This is particularly the case where there is a high degree of overlap between the polygons. In this case, <code>buffer(0)</code> is forced to compute with <em>all</em> line segments from the outset, whereas cascading can eliminate many segments at each stage of processing. The best case for buffer(0) is the trivial case where there is <em>no</em> overlap between the input geometries. However, this case is likely rare in practice. </p>
<hr/><h2>Constructor & Destructor Documentation</h2>
<a class="anchor" id="a056d0965591c58d015e1bc5b924a9999"></a><!-- doxytag: member="geos::operation::geounion::CascadedPolygonUnion::CascadedPolygonUnion" ref="a056d0965591c58d015e1bc5b924a9999" args="(std::vector< geom::Polygon * > *polys)" -->
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<td class="memname">geos::operation::geounion::CascadedPolygonUnion::CascadedPolygonUnion </td>
<td>(</td>
<td class="paramtype">std::vector< <a class="el" href="classgeos_1_1geom_1_1Polygon.html">geom::Polygon</a> * > * </td>
<td class="paramname"> <em>polys</em></td>
<td> ) </td>
<td><code> [inline]</code></td>
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<p>Creates a new instance to union the given collection of <a class="el" href="">Geometry</a>s.</p>
<dl><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>geoms</em> </td><td>a collection of <a class="el" href="">Polygonal</a> <a class="el" href="">Geometry</a>s </td></tr>
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</dd>
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<hr/><h2>Member Function Documentation</h2>
<a class="anchor" id="a721608ec9629555af43648ddd32c19b8"></a><!-- doxytag: member="geos::operation::geounion::CascadedPolygonUnion::Union" ref="a721608ec9629555af43648ddd32c19b8" args="(std::vector< geom::Polygon * > *polys)" -->
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<td class="memname">static <a class="el" href="classgeos_1_1geom_1_1Geometry.html">geom::Geometry</a>* geos::operation::geounion::CascadedPolygonUnion::Union </td>
<td>(</td>
<td class="paramtype">std::vector< <a class="el" href="classgeos_1_1geom_1_1Polygon.html">geom::Polygon</a> * > * </td>
<td class="paramname"> <em>polys</em></td>
<td> ) </td>
<td><code> [static]</code></td>
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<p>Computes the union of a collection of <a class="el" href="">Polygonal</a> <a class="el" href="">Geometry</a>s.</p>
<dl><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>polys</em> </td><td>a collection of <a class="el" href="">Polygonal</a> <a class="el" href="">Geometry</a>s </td></tr>
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</dd>
</dl>
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<a class="anchor" id="a85d370411643071a75f507b604412ce2"></a><!-- doxytag: member="geos::operation::geounion::CascadedPolygonUnion::Union" ref="a85d370411643071a75f507b604412ce2" args="()" -->
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<td class="memname"><a class="el" href="classgeos_1_1geom_1_1Geometry.html">geom::Geometry</a>* geos::operation::geounion::CascadedPolygonUnion::Union </td>
<td>(</td>
<td class="paramname"></td>
<td> ) </td>
<td></td>
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<div class="memdoc">
<p>Computes the union of the input geometries.</p>
<dl class="return"><dt><b>Returns:</b></dt><dd>the union of the input geometries </dd>
<dd>
null if no input geometries were provided </dd></dl>
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</div>
<a class="anchor" id="ab2137d4ee76db279ce43fa719c77cbf7"></a><!-- doxytag: member="geos::operation::geounion::CascadedPolygonUnion::Union" ref="ab2137d4ee76db279ce43fa719c77cbf7" args="(const geom::MultiPolygon *polys)" -->
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<td class="memname">static <a class="el" href="classgeos_1_1geom_1_1Geometry.html">geom::Geometry</a>* geos::operation::geounion::CascadedPolygonUnion::Union </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="classgeos_1_1geom_1_1MultiPolygon.html">geom::MultiPolygon</a> * </td>
<td class="paramname"> <em>polys</em></td>
<td> ) </td>
<td><code> [static]</code></td>
</tr>
</table>
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<div class="memdoc">
<p>Computes the union of a collection of <a class="el" href="">Polygonal</a> <a class="el" href="">Geometry</a>s.</p>
<dl><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>polys</em> </td><td>a collection of <a class="el" href="">Polygonal</a> <a class="el" href="">Geometry</a>s </td></tr>
</table>
</dd>
</dl>
</div>
</div>
<hr/>The documentation for this class was generated from the following file:<ul>
<li><a class="el" href="CascadedPolygonUnion_8h_source.html">CascadedPolygonUnion.h</a></li>
</ul>
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