判断俩直线相交代码//fC什么意思?
bool lineIntersectSide(Point A, Point B, Point C, Point D)
{
// A(x1, y1), B(x2, y2)的直线方程为：
// f(x, y) = (y - y1) * (x1 - x2) - (x - x1) * (y1 - y2) = 0
float fC = (C.y - A.y) * (A.x - B.x) - (C.x - A.x) * (A.y - B.y);
float fD = (D.y - A.y) * (A.x - B.x) - (D.x - A.x) * (A.y - B.y);
if(fC * fD > 0)
return false;
return true;
}
bool sideIntersectSide(Point A, Point B, Point C, Point D)
{
if(!lineIntersectSide(A, B, C, D))
return false;
if(!lineIntersectSide(C, D, A, B))
return false;
return true;
}
