//空间直线
template <class T>
class LineSegment
{
public:
    Vec3<T> startPoint;
    Vec3<T> endPoint;
    Vec3<T> direction;
    Vec3<T> min;
    Vec3<T> max;
    LineSegment()
    {
    }
    LineSegment(Vec3<T> start, Vec3<T> end)
    {
        startPoint = start;
        endPoint = end;
        direction = end - start;      
    }
    inline void Set(Vec3<T> start, Vec3<T> end)
    {
        startPoint = start;
        endPoint = end;
        direction = end - start;      
    }
    //两条线段相交
    inline static bool Intersection2D(LineSegment & line1, LineSegment & line2, Vec3<T>& insPoint)
    {
        double D = -line1.direction.x() * line2.direction.y() + line1.direction.y() * line2.direction.x();
        if(D == 0.0)
        {
            return false;
        }
        auto O12 = line2.startPoint - line1.startPoint;
        T D1 = -O12.x() * line2.direction.y() + O12.y() * line2.direction.x();
        T D2 = line1.direction.x() * O12.y() - line1.direction.y() * O12.x();
        T t1 = D1 / D;
        if(t1<0 || t1 > 1)
        {
            return false;
        }
        T t2 = D2 / D;
        if(t2<0 || t2 > 1)
        {
            return false;
        }
        insPoint = line1.startPoint + line1.direction * t1;     //这样计算得到的Z值是不准确的
        return true;
    }
    //线段与矩形相交
    inline bool static IsIntersectsOrthogon2D(LineSegment & line, Orthogon<T> orthogon)
    {
        if (orthogon.IsContainsPoint(line.startPoint.x(), line.startPoint.y()) ||
                orthogon.IsContainsPoint(line.endPoint.x(), line.endPoint.y()))
        {
            return true;
        }
        LineSegment diagonal1(Vec3<T>(orthogon.minX(), orthogon.minY(), 0),
                              Vec3<T>(orthogon.maxX(), orthogon.maxY(), 0));
        LineSegment diagonal2(Vec3<T>(orthogon.minX(), orthogon.maxY(), 0),
                              Vec3<T>(orthogon.maxX(), orthogon.minY(), 0));
        Vec3<T> point(0,0,0);
        return Intersection2D(line, diagonal1, point) || Intersection2D(line, diagonal2, point);
    }
};