/// <summary>
/// Compare two sweep events.
/// </summary>
/// <param name="e1"></param>
/// <param name="e2"></param>
/// <returns>True when e1 should be placed before e2, i.e. e1 should be handled after e2</returns>
public static int CompareTo(SweepEvent e1, SweepEvent e2)
{
if (e1.Point.x > e2.Point.x) // Different x-coordinate
{
return(1);
}
if (e1.Point.x < e2.Point.x) // Different x-coordinate
{
return(-1);
}
if (!e1.Point.y.Equals(e2.Point.y)
) // Different points, but same x-coordinate. The event with lower y-coordinate is processed first
{
return(e1.Point.y > e2.Point.y ? 1 : -1);
}
if (e1.IsStart != e2.IsStart
) // Same point, but one is a left endpoint and the other a right endpoint. The right endpoint is processed first.
{
return(e1.IsStart ? 1 : -1);
}
// Same point, but events are left endpoints or both are right endpoints.
if (MathUtil.SignedArea(e1.Point, e1.OtherEvent.Point, e2.OtherEvent.Point) != 0)
{
// Not collinear
return
(e1.Above(e2.OtherEvent.Point)
? 1
: -1); // The event associated to the bottom segment is processed first
}
// Collinear
return(e1.PolygonType > e2.PolygonType ? 1 : -1);
}
