[Boost-users] [Polygon] How to put self intersect polygon into PolygonSet

Subject: [Boost-users] [Polygon] How to put self intersect polygon into PolygonSet
From: zeal (li.y-neu_at_[hidden])
Date: 2012-09-27 04:25:09

Hi,

I'm just searching for a polygon Boolean library and I found this Boost.Polygon, but I met a problem with self intersect polygon.
like below:
    typedef gtl::polygon_data<int> Polygon;
    std::vector<Polygon >  ps;

    typedef Polygon::point_type Point;
    Point pts[] = 
    {
       gtl::construct<Point>(0, 0),
       gtl::construct<Point>(10, 10),
       gtl::construct<Point>(10, 0), 
       gtl::construct<Point>(0, 10)
    };
    Polygon poly;
    gtl::set_points(poly, pts, pts+ sizeof(pts)/sizeof(Point));
    ps += poly;

I want to put a self intersect polygon

|\    /|
| \  / |
|  \/  |
|  /\  |
| /  \ |
|/    \|
into a Polygon set ps,
But when I use ps += poly to put it, in the ps the polygon has been cut to
      /|
     / |
    /  |
    \  |
     \ |
      \|

and the left part doesn't exist anymore.
I'm not sure whether I use it in a wrong way, or the library doesn't support this kind of operation?

Best regards,

Zeal

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