const collision line_line(const line &a, const line &b)
{
collision r;
auto m1 = (a.position.y - a.end.y) / (a.position.x - a.end.x);
auto m2 = (b.position.y - b.end.y) / (b.position.x - b.end.x);
auto b1 = a.position.y - m1*a.position.x;
auto b2 = b.position.y - m2*b.position.x;
float x = (b2 - b1) / (m1 - m2);
float y = m1*x + b1;
if ((a.position.x - a.end.x) == 0) // if a is a vertical line, then there is only 1 possible x value.
{ x = a.position.x; y = m2 *x + b2; }
if ((b.position.x - b.end.x) == 0)
{ x = b.position.x; y = m1 *x + b1; }
r.contact = { x, y }; point p(r.contact);
r.result = circle_point(circle(a.mid(), a.length() / 2), p).result
&& circle_point(circle(b.mid(), b.length() / 2), p).result;
if (m1 == m2)
{
r.result = false;
return r;
}
return r;
}
bool is_laying(construction_line<T1> const & src, line<Pt2> const & target)
{
typedef typename quan::meta::binary_op<
T1, quan::meta::minus,typename Pt2::value_type
>::type value_type;
construction_line<value_type> cons_target(target.from,target.to - target.from);
std::pair<bool,quan::two_d::vect<value_type> > intersect_pt = intersect(src,cons_target);
if (!intersect_pt.first) {
return false;
}
typename value_type mag_target = target.length();
quan::two_d::vect<value_type> v1 (target.from - intersect_pt.second);
if (magnitude(v1) > mag_target) return false;
quan::two_d::vect<value_type> v2 (target.to -intersect_pt.second);
if(magnitude(v2) > mag_target) return false;
return true;
}