/*
* Checks whether two lines intersect or not
* @see http://local.wasp.uwa.edu.au/~pbourke/geometry/lineline2d/
* adapted from line_line_intersection
*/
std::pair<int, int>
FlatRay::IntersectsRatio(const FlatRay &that) const
{
std::pair<int, int> r;
r.second = vector.CrossProduct(that.vector);
if (r.second == 0)
// lines are parallel
return r;
const FlatGeoPoint delta = that.point - point;
r.first = delta.CrossProduct(that.vector);
if ((sgn(r.first) * sgn(r.second) < 0) || (abs(r.first) > abs(r.second))) {
// outside first line
r.second = 0;
return r;
}
const int ub = delta.CrossProduct(vector);
if ((sgn(ub) * sgn(r.second) < 0) || (abs(ub) > abs(r.second))) {
// outside second line
r.second = 0;
return r;
}
// inside both lines
return r;
}
bool
FlatTriangleFan::IsInside(FlatGeoPoint p) const
{
if (!bounding_box.IsInside(p))
return false;
bool inside = false;
for (auto i = vs.begin(), j = std::prev(vs.end()), end = vs.end();
i != end; j = i++) {
if ((i->y > p.y) == (j->y > p.y))
continue;
const FlatGeoPoint ji = *j - *i;
const FlatGeoPoint pi = p - *i;
if (pi.CrossProduct(ji) < 0)
inside = !inside;
}
return inside;
}
