////////////////////////////////////////////////////////////////////////////////////////////////////
/// <summary> Create a circle event from a triple of leaf nodes. </summary>
/// <remarks> Darrellp, 2/18/2011. </remarks>
/// <param name="lfnLeft"> Leaf node representing the leftmost parabola. </param>
/// <param name="lfnCenter"> Leaf node representing the center parabola. </param>
/// <param name="lfnRight"> Leaf node representing the rightmost parabola. </param>
/// <param name="yScanLine"> Where the scan line is located. </param>
/// <param name="evq"> Event queue. </param>
////////////////////////////////////////////////////////////////////////////////////////////////////
private static void CreateCircleEventFromTriple(
LeafNode lfnLeft,
LeafNode lfnCenter,
LeafNode lfnRight,
double yScanLine,
EventQueue evq)
{
// This happens if we're the farthest right or left parabola...
if (lfnLeft == null || lfnRight == null || lfnCenter == null)
{
// No circle events associated with non-existent parabolas
return;
}
// We need at least three points
if (lfnRight == lfnCenter || lfnRight == lfnLeft || lfnCenter == lfnLeft)
{
// If two of the points are identical then we don't have three points
return;
}
// Make sure we don't insert the same circle eventin twice
if (ICcwVoronoi(lfnLeft.Poly.VoronoiPoint, lfnCenter.Poly.VoronoiPoint, lfnRight.Poly.VoronoiPoint) > 0)
{
// Don't create an event if we've already put it in before
return;
}
// Create the circle event
var cevt = FortuneEvent.CreateCircleEvent(lfnLeft.Poly, lfnCenter.Poly, lfnRight.Poly, yScanLine);
// If we got a valid circle event
if (cevt != null)
{
// Indicate which leaf node gets snuffed when this event is handled
cevt.LfnEliminated = lfnCenter;
// Add it to the event queue
evq.AddCircleEvent(cevt);
// Let the center node know this event will bring about its ominous demise
lfnCenter.SetCircleEvent(cevt);
}
}
