polygon_overlap_area.cpp

#include "polygon_overlap_area.hpp"

PolygonOverlap::PolygonOverlap(void):gen(0){}

double PolygonOverlap::PolyArea(vector<Vector2D> const& polygon)
{
  int ntriangles=static_cast<int>(polygon.size())-2;
        if(ntriangles<1)
                return 0;
        double res=0;
        for(size_t i=0;i<static_cast<size_t>(ntriangles);++i)
                res+=fabs(CrossProduct(polygon[i+1]-polygon[0],polygon[i+2]
                        -polygon[0]));
        return 0.5*res;
}

double PolygonOverlap::polygon_overlap_area(vector<Vector2D> const& ch1,
        vector<Vector2D> const& ch2,double R0,double R1)
{
        vector<Vector2D> p(ch1),q(ch2);
        double r[2];
        int n=static_cast<int>(p.size());
        boost::random::uniform_real_distribution<> dist(-1,1);
        for(size_t i=0;i<static_cast<size_t>(n);++i)
        {
                r[0]=2*dist(gen)-1;
                r[1]=2*dist(gen)-1;
                p[i].Set(p[i].x+r[0]*R0,p[i].y+r[1]*R0);
        }
        n=static_cast<int>(q.size());
        for(size_t i=0;i<static_cast<size_t>(n);++i)
        {
                r[0]=2*dist(gen)-1;
                r[1]=2*dist(gen)-1;
                q[i].Set(q[i].x+r[0]*R1,q[i].y+r[1]*R1);
        }
        vector<Vector2D> poly=ConvexIntersect(p,q);
        return PolyArea(poly);
}