public static Intersection FindIntersection(this Polygon polygon, IntPoint start, IntPoint end, QuadTree <int> edgeQuadTree = null)
{
Intersection bestIntersection = Intersection.None;
IntPoint segmentDelta = end - start;
var edgeIterator = new PolygonEdgeIterator(polygon, 1, edgeQuadTree);
foreach (var i in edgeIterator.GetTouching(new Quad(start, end)))
{
IntPoint edgeStart = polygon[i];
// if we share a vertex we cannot be crossing the line
IntPoint edgeEnd = polygon[(i + 1) % polygon.Count];
if (start == edgeStart || start == edgeEnd || end == edgeStart || end == edgeEnd ||
start == polygon[i] || end == polygon[i])
{
bestIntersection = Intersection.Colinear;
}
else
{
var result = GetIntersection(start, end, edgeStart, edgeEnd);
if (result == Intersection.Intersect)
{
return(Intersection.Intersect);
}
else if (result == Intersection.Colinear)
{
bestIntersection = Intersection.Colinear;
}
}
}
return(bestIntersection);
}
public static IEnumerable <Tuple <int, IntPoint> > FindCrossingPoints(this Polygon polygon, IntPoint start, IntPoint end, QuadTree <int> edgeQuadTree = null)
{
IntPoint segmentDelta = end - start;
long segmentLength = segmentDelta.Length();
var edgeIterator = new PolygonEdgeIterator(polygon, 1, edgeQuadTree);
foreach (var i in edgeIterator.GetTouching(new Quad(start, end)))
{
IntPoint edgeStart = polygon[i];
IntPoint edgeEnd = polygon[(i + 1) % polygon.Count];
IntPoint intersection = new IntPoint();
if (OnSegment(edgeStart, start, edgeEnd))
{
yield return(new Tuple <int, IntPoint>(i, start));
}
else if (OnSegment(edgeStart, end, edgeEnd))
{
yield return(new Tuple <int, IntPoint>(i, end));
}
else if (DoIntersect(start, end, edgeStart, edgeEnd) &&
CalcIntersection(start, end, edgeStart, edgeEnd, out intersection))
{
IntPoint pointRelStart = intersection - start;
yield return(new Tuple <int, IntPoint>(i, intersection));
}
}
}
