CODEWITHSUNDEEP
computational-geometrycgal
Ivan Xiao
Ivan Xiao

Reputation: 1969

CGAL: Intersection between a segment and a polygon?

I have a set of polygons and I want to test intersection between it and a segment. I checked the manual but I cannot find a matching function. The intersection between points, lines, segments, triangles, planes do exist. And the intersection between polygons are also there. My question is:

  1. Is there such a function?
  2. If not, does it mean I need to break down the polygons into segments and do intersection among these segments? (The reason that I am reluctant to do this is, I thought CGAL might in fact use this way to do intersections between polygons. How come there is no such a function for intersecting a line and a polygon?) Or is there any other better way to do it?

Upvotes: 7

Views: 4782

Answers (1)

kirilsolo
kirilsolo

Reputation: 196

The easiest method is to create a Polygon_set_2 object which may contain several polygons. To test an intersection of an external polygon with this set you simply apply the do_intersect method.

For example:

typedef CGAL::Polygon_set_2<Kernel, std::vector<Kernel::Point_2>> Polygon_set_2;
Polygon_set_2 ps;
Polygon_2     poly;
Polygon_2     line; // line is a polygon defined by 2 points

ps.insert(poly);
bool intersect = ps.do_intersect(line);

More on polygon_set_2:

I hope it's clear, Kiril

Upvotes: 7

Related Questions