Line2(ref Vector2 pt1, ref Vector2 pt2)
{
p1 = pt1;
p2 = pt2;
a = p2.y - p1.y;
b = p1.x - p2.x;
c = p2.x * p1.y - p1.x * p2.y;
#if UNITY_EDITOR
if (Math2d.Approximately(a, 0.0f) && Math2d.Approximately(b, 0.0f))
{
Debug.LogError("DistanceFromPoint Zero!");
}
#endif
}