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    <p>You may also check out the rtree variants provided by the Boost.Geometry library:</p> <p><a href="http://www.boost.org/doc/libs/release/libs/geometry/doc/html/geometry/spatial_indexes.html" rel="noreferrer">http://www.boost.org/doc/libs/release/libs/geometry/doc/html/geometry/spatial_indexes.html</a></p> <p>Boost.Geometry rtree implementation allows storing values of arbitrary type in the spatial index and performing complex queries. Parameters like maximum node elements may be passed as compile- or run-time parameters. It supports C++11 move semantics also emulated on pre-C++11 compilers thanks to Boost.Move. It also supports stateful allocators which allows e.g. to store the rtree in a shared memory using Boost.Interprocess. And it's fast.</p> <p>On the down-side, currently persistent storage isn't yet supported so if you need more than in-memory spatial index you should probably check one of the other mentioned libraries.</p> <p><strong>Quick example:</strong></p> <p>Probably the most common use case is when you store some geometric objects in a container and their bounding boxes with some ids in the spatial index. In case of Boost.Geometry rtree this could look like this:</p> <pre><code>#include &lt;boost/geometry.hpp&gt; #include &lt;boost/geometry/index/rtree.hpp&gt; #include &lt;vector&gt; namespace bg = boost::geometry; namespace bgi = boost::geometry::index; /* The definition of my_object type goes here */ int main() { typedef bg::model::point&lt;float, 2, bg::cs::cartesian&gt; point; typedef bg::model::box&lt;point&gt; box; typedef std::pair&lt;box, size_t&gt; value; std::vector&lt;my_object&gt; objects; /* Fill objects */ // create the R* variant of the rtree bgi::rtree&lt; value, bgi::rstar&lt;16&gt; &gt; rtree; // insert some values to the rtree for ( size_t i = 0 ; i &lt; objects.size() ; ++i ) { // create a box box b = objects[i].calculate_bounding_box(); // insert new value rtree.insert(std::make_pair(b, i)); } // find values intersecting some area defined by a box box query_box(point(0, 0), point(5, 5)); std::vector&lt;value&gt; result_s; rtree.query(bgi::intersects(query_box), std::back_inserter(result_s)); // find 5 nearest values to a point std::vector&lt;value&gt; result_n; rtree.query(bgi::nearest(point(0, 0), 5), std::back_inserter(result_n)); return 0; } </code></pre>
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    1. USAdam Wulkiewicz
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    1. CO+1 for giving an example with the Boost library
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