public SegmentsIntersectionResult Intersect(Segment other)
{
var result = new SegmentsIntersectionResult();
result.IsIntersection = false;
var S = P2 - P1;
var otherS = other.P2 - other.P1;
//t = (other.P1 − P1) × otherS / (S × otherS)
//u = (other.P1 − P1) × S / (S × otherS)
var otherP1ToP1 = (other.P1 - P1);
var den = S * otherS;
var t = otherP1ToP1 * otherS;
var u = otherP1ToP1 * S;
//Actually it's more complex than this, if only one is 0 it means parallel, otherwise coincident
if (t == 0 || u == 0 || den == 0)
return result;
t /= den;
u /= den;
if (t < 0 || t > 1 || u < 0 || u > 1)
return result;
result.IsIntersection = true;
result.Point = P1 + S * t;
var otherLeftNormal = otherS.Rotated90CCW.Normalized;
var projOnNormal = (-otherP1ToP1).Dot(otherLeftNormal);
if (projOnNormal > 0)
result.Normal = otherLeftNormal;
else
result.Normal = -otherLeftNormal;
return result;
}
private static Boolean IntersectAnyPolygonEdgeExceptLast(Polygon polygon, DblPoint2 p1, DblPoint2 p2)
{
var s12 = new Segment(p1, p2);
for (var i = 0; i < polygon.Points.Count - 1; i++)
{
var result = new Segment(polygon.Points[i], polygon.Points[i + 1]).Intersect(s12);
if (result.IsIntersection)
return true;
}
return false;
}
