Hi and welcome, Zhang Qun Via Boost-users wrote:
Hi guys, first-time post here. Hello to everyone.
I'm using boost.geometry to implement a project. I need to calculate the intersection between a line and a polygon. I know there is no infinite line concept in boost.geometry. So I try to use the segment to intersect with a polygon, however, it seems not supported yet. Is there any other workaround that I can implement the intersection between a line and a polygon? The line is like y=mx+b or ax + by + c = 0.
Indeed the intersection of segment and polygon does not compile even though it should. Fortunately you can represent a segment as a linestring with 2 points. Something like this: namespace bg = boost::geometry; typedef bg::model::point<double, 2, bg::cs::cartesian> point; typedef bg::model::box<point> box; typedef bg::model::segment<point> segment; typedef bg::model::linestring<point> linestring; typedef bg::model::multi_linestring<linestring> multi_linestring; typedef bg::model::polygon<point> polygon; // create some polygon, a circle polygon poly; for (double a = 0; a < 2 * 3.14; a += 0.1) bg::append(poly, point(cos(a), sin(a))); // correct data to match compile-time metadata // (clockwise, closed polygon) bg::correct(poly); // calculate polygon's bounding box which could be used with line // equation to calculate segment's endpoints box b = bg::return_envelope<box>(poly); // here you could calculate a segment represented as linestring // using min and max coordinates of polygon's envelope // and line's parameters // but for now: linestring ls; bg::append(ls, point(-1, -1)); bg::append(ls, point(1, 1)); // the result of the intersection of linear and areal geometry // is multi-linestring multi_linestring result; bg::intersection(ls, poly, result); std::cout << bg::wkt(ls) << std::endl; std::cout << bg::wkt(poly) << std::endl; std::cout << bg::wkt(result) << std::endl; Regards, Adam