internal static bool AnyIntersections(PlanarGraph <double> graph)
{
if (graph == null)
{
return(false);
}
SegmentGroup <double> activeEdges = new SegmentGroup <double>();
IEnumerator <Node <double> > points = graph.GetEnumerator(); //walk through the points in xy sorted order
Node <double> nd;
LeakyResizableArray <Edge <double> > localEdges;
int localCt;
int activeCt = 0;
Edge <double> localEdge;
LineIntersectionResult <double> intersects;
Point2 <double> localStart;
Point2 <double> localEnd;
Point2 <double> activeStart;
Point2 <double> activeEnd;
//new point event in the moving front
while (points.MoveNext())
{
nd = points.Current;
localEdges = nd.Edges; //edges connected to this point
localCt = (int)localEdges.Count;
//compute intersections with other edges in the scan area
for (int i = 0; i < localCt; i++)
{
localEdge = localEdges.Data[i];
localStart = localEdge.Start.Point;
localEnd = localEdge.End.Point;
activeCt = activeEdges.Edges.Count;
foreach (Edge <double> activeEdge in activeEdges)
{
if (object.ReferenceEquals(localEdge, activeEdge))
{
continue; //can't have a "full" match -- this is an exiting segment
}
activeStart = activeEdge.Start.Point;
activeEnd = activeEdge.End.Point;
intersects = Coordinate2Utils.GetIntersection(localStart.X, localStart.Y, localEnd.X, localEnd.Y, activeStart.X, activeStart.Y, activeEnd.X, activeEnd.Y);
if (intersects.IntersectionType != LineIntersectionType.NoIntersection)
{
if (intersects.IntersectionType == LineIntersectionType.CollinearIntersection)
{
return(true); // there's a full segment of intersection
}
if (object.ReferenceEquals(localEdge.Previous, activeEdge) || object.ReferenceEquals(localEdge.Next, activeEdge))
{
continue; // this intersection is a single point at the common point of adjacent segments in a chain/ring
}
return(true);
}
}
}
//remove all exiting segments and add all starting segments
//Action gets called exactly twice per edge -- once to add it, once to remove it
for (int i = 0; i < localCt; i++)
{
activeEdges.Action(localEdges.Data[i]);
}
}
return(false);
}