...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Let the buffer create rounded ends.
This strategy can be used as EndStrategy for the buffer algorithm. It creates a rounded end for each linestringend. It can be applied for (multi)linestrings. Also it is applicable for spikes in (multi)polygons. This strategy is only applicable for Cartesian coordinate systems.
class strategy::buffer::end_round { // ... };
Function 
Description 
Parameters 

end_round(std::size_t points_per_circle = 90)

Constructs the strategy. 
std::size_t: points_per_circle: points which would be used for a full circle (if points_per_circle is smaller than 4, it is internally set to 4) 
#include <boost/geometry/strategies/cartesian/buffer_end_round.hpp>
Shows how the end_round strategy can be used as a EndStrategy to create rounded ends
#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::linestring<point> linestring; typedef boost::geometry::model::polygon<point> polygon; // Declare the roundend strategy with 36 points for a full circle boost::geometry::strategy::buffer::end_round end_strategy(36); // Declare other strategies boost::geometry::strategy::buffer::distance_symmetric<double> distance_strategy(1.0); boost::geometry::strategy::buffer::side_straight side_strategy; boost::geometry::strategy::buffer::join_round join_strategy; boost::geometry::strategy::buffer::point_circle point_strategy; // Declare/fill a multi linestring boost::geometry::model::multi_linestring<linestring> ml; boost::geometry::read_wkt("MULTILINESTRING((3 5,5 10,7 5),(7 7,11 10,15 7,19 10))", ml); // Create the buffered geometry with rounded ends boost::geometry::model::multi_polygon<polygon> result; boost::geometry::buffer(ml, result, distance_strategy, side_strategy, join_strategy, end_strategy, point_strategy); return 0; }