/// <summary>
/// halfEdge should be Upper->Lower so that the persistent half edges become:
/// o halfEdge (Upper->Lower) ==> (vertex->Lower)
/// o halfEdge.Twin (Lower->Upper) ==> (Lower->vertex)
/// And the two newly created half edges are (vertex->Upper) and (Upper->vertex).
/// </summary>
private static void SplitEdge(DCEL_Subdivision subdivision, DCEL_HalfEdge halfEdge, DCEL_Vertex vertex)
{
Debug.Assert(VecRat2.CompareReadingOrder(halfEdge.Origin.Position, halfEdge.Destination.Position) < 0);
DCEL_HalfEdge e1 = halfEdge;
DCEL_HalfEdge e2 = e1.Twin;
DCEL_HalfEdge e1_prev = e1.Prev;
DCEL_HalfEdge e2_next = e2.Next;
DCEL_Vertex e1_origin = e1.Origin;
DCEL_HalfEdge e1_top = new DCEL_HalfEdge();
DCEL_HalfEdge e2_top = new DCEL_HalfEdge();
DCEL_Helper.JoinTwin(e1_top, e2_top);
e1_top.IncidentFace = e1.IncidentFace;
e2_top.IncidentFace = e2.IncidentFace;
DCEL_Helper.JoinIncidentEdge(vertex, e2_top);
DCEL_Helper.JoinIncidentEdge(vertex, e1);
DCEL_Helper.JoinIncidentEdge(e1_origin, e1_top);
if (e2_next == e1)
{
DCEL_Helper.JoinNext(e2, e2_top);
DCEL_Helper.JoinNext(e2_top, e1_top);
DCEL_Helper.JoinNext(e1_top, e1);
}
else
{
DCEL_Helper.JoinPrevNext(e2, e2_top, e2_next);
DCEL_Helper.JoinPrevNext(e1_prev, e1_top, e1);
}
if (subdivision != null)
{
subdivision.HalfEdges.Add(new RBTreeSetNode <DCEL_HalfEdge>(e1_top));
subdivision.HalfEdges.Add(new RBTreeSetNode <DCEL_HalfEdge>(e2_top));
}
}
public int CompareTo(DCEL_Vertex other)
{
return(VecRat2.CompareReadingOrder(this.Position, other.Position));
}