public static VNode ProcessCircleEvent(VCircleEvent e, VNode Root, VoronoiGraph VG, float ys, out VDataNode[] CircleCheckList)
        {
            VDataNode a, b, c;
            VEdgeNode eu, eo;
            b = e.NodeN;
            a = VNode.LeftDataNode(b);
            c = VNode.RightDataNode(b);
            if (a == null || b.Parent == null || c == null || !a.DataPoint.Equals(e.NodeL.DataPoint) || !c.DataPoint.Equals(e.NodeR.DataPoint))
            {
                CircleCheckList = new VDataNode[] { };
                return Root; // Abbruch da sich der Graph verändert hat
            }
            eu = (VEdgeNode)b.Parent;
            CircleCheckList = new VDataNode[] { a, c };
            //1. Create the new Vertex
            Vector2 VNew = new Vector2(e.Center.x, e.Center.y);
            //			VNew[0] = Fortune.ParabolicCut(a.DataPoint[0],a.DataPoint[1],c.DataPoint[0],c.DataPoint[1],ys);
            //			VNew[1] = (ys + a.DataPoint[1])/2 - 1/(2*(ys-a.DataPoint[1]))*(VNew[0]-a.DataPoint[0])*(VNew[0]-a.DataPoint[0]);
            VG.Vertices.Add(VNew);
            //2. Find out if a or c are in a distand part of the tree (the other is then b's sibling) and assign the new vertex
            if (eu.Left == b) // c is sibling
            {
                eo = VNode.EdgeToRightDataNode(a);

                // replace eu by eu's Right
                eu.Parent.Replace(eu, eu.Right);
            }
            else // a is sibling
            {
                eo = VNode.EdgeToRightDataNode(b);

                // replace eu by eu's Left
                eu.Parent.Replace(eu, eu.Left);
            }
            eu.Edge.AddVertex(VNew);
            //			///////////////////// uncertain
            //			if(eo==eu)
            //				return Root;
            //			/////////////////////
            eo.Edge.AddVertex(VNew);
            //2. Replace eo by new Edge
            VoronoiEdge VE = new VoronoiEdge();
            VE.Left = a.DataPoint;
            VE.Right = c.DataPoint;
            VE.AddVertex(VNew);
            VG.Edges.Add(VE);

            VEdgeNode VEN = new VEdgeNode(VE, false);
            VEN.Left = eo.Left;
            VEN.Right = eo.Right;
            if (eo.Parent == null)
                return VEN;
            eo.Parent.Replace(eo, VEN);
            return Root;
        }
 public static VCircleEvent CircleCheckDataNode(VDataNode n, float ys)
 {
     VDataNode l = VNode.LeftDataNode(n);
     VDataNode r = VNode.RightDataNode(n);
     if (l == null || r == null || l.DataPoint == r.DataPoint || l.DataPoint == n.DataPoint || n.DataPoint == r.DataPoint)
         return null;
     if (MathTools.ccw(l.DataPoint, n.DataPoint, r.DataPoint, false) <= 0)
         return null;
     Vector2 Center = Fortune.CircumCircleCenter(l.DataPoint, n.DataPoint, r.DataPoint);
     VCircleEvent VC = new VCircleEvent();
     VC.NodeN = n;
     VC.NodeL = l;
     VC.NodeR = r;
     VC.Center = Center;
     VC.Valid = true;
     if (VC.Y >= ys)
         return VC;
     return null;
 }