Boost C++ Libraries

Let the buffer create sharp corners.

Description

This strategy can be used as JoinStrategy for the buffer algorithm. It creates a sharp corners around each convex vertex. It can be applied for (multi)linestrings and (multi)polygons. If corners are sharp by themselves, the miters might become very long. Therefore there is a limit (miter_limit), in terms of the used distance, which limits their length. The miter is not changed to a bevel form (as done in some other software), it is just adapted to the specified miter_limit but keeps its miter form. If the buffer distance is 5.0, and the miter limit is 2.0, generated points will be located at a distance of at most 10.0 (2*5) units. This strategy is only applicable for Cartesian coordinate systems.

Synopsis

class strategy::buffer::join_miter
{
  // ...
};

Constructor(s)

join_miter(double miter_limit = 5.0)

Header

#include <boost/geometry/strategies/cartesian/buffer_join_miter.hpp>

Example

Shows how the join_miter strategy can be used as a JoinStrategy to create sharp corners

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/geometries.hpp>


int main()
{
    typedef boost::geometry::model::d2::point_xy<double> point;
    typedef boost::geometry::model::polygon<point> polygon;

    // Declare the join_miter strategy
    boost::geometry::strategy::buffer::join_miter join_strategy;

    // Declare other strategies
    boost::geometry::strategy::buffer::distance_symmetric<double> distance_strategy(0.5);
    boost::geometry::strategy::buffer::end_flat end_strategy;
    boost::geometry::strategy::buffer::side_straight side_strategy;
    boost::geometry::strategy::buffer::point_circle point_strategy;

    // Declare/fill a multi polygon
    boost::geometry::model::multi_polygon<polygon> mp;
    boost::geometry::read_wkt("MULTIPOLYGON(((5 5,7 8,9 5,5 5)),((8 7,8 10,11 10,11 7,8 7)))", mp);

    // Create the buffered geometry with sharp corners
    boost::geometry::model::multi_polygon<polygon> result;
    boost::geometry::buffer(mp, result,
                distance_strategy, side_strategy,
                join_strategy, end_strategy, point_strategy);


    return 0;
}

Output

See also