private void MeshCleanReq( DelaunayTriangle triangle ) {
			if (triangle != null && !triangle.IsInterior) {
				triangle.IsInterior = true;
				Triangulatable.AddTriangle(triangle);

				for (int i = 0; i < 3; i++)
				if (!triangle.EdgeIsConstrained[i])
				{
					MeshCleanReq(triangle.Neighbors[i]);
				}
			}
		}

		public void RemoveFromList( DelaunayTriangle triangle ) {
			Triangles.Remove(triangle);
			// TODO: remove all neighbor pointers to this triangle
			//        for( int i=0; i<3; i++ )
			//        {
			//            if( triangle.neighbors[i] != null )
			//            {
			//                triangle.neighbors[i].clearNeighbor( triangle );
			//            }
			//        }
			//        triangle.clearNeighbors();
		}

        private static void FlipEdgeEvent(DTSweepContext tcx, TriangulationPoint ep, TriangulationPoint eq, DelaunayTriangle t, TriangulationPoint p)
        {
            DelaunayTriangle ot = t.NeighborAcross(p);
            TriangulationPoint op = ot.OppositePoint(t, p);

            if (ot == null)
            {
                // If we want to integrate the fillEdgeEvent do it here
                // With current implementation we should never get here
                throw new InvalidOperationException("[BUG:FIXME] FLIP failed due to missing triangle");
            }

            if (t.GetConstrainedEdgeAcross(p))
            {
                throw new Exception("Intersecting Constraints");
            }

            bool inScanArea = TriangulationUtil.InScanArea(p, t.PointCCW(p), t.PointCW(p), op);
            if (inScanArea)
            {
                // Lets rotate shared edge one vertex CW
                RotateTrianglePair(t, p, ot, op);
                tcx.MapTriangleToNodes(t);
                tcx.MapTriangleToNodes(ot);

                if (p == eq && op == ep)
                {
                    if (eq == tcx.EdgeEvent.ConstrainedEdge.Q
                        && ep == tcx.EdgeEvent.ConstrainedEdge.P)
                    {
                        t.MarkConstrainedEdge(ep, eq);
                        ot.MarkConstrainedEdge(ep, eq);
                        Legalize(tcx, t);
                        Legalize(tcx, ot);
                    }
                    else
                    {
                        // XXX: I think one of the triangles should be legalized here?
                    }
                }
                else
                {
                    // TODO: remove
                    Orientation o = TriangulationUtil.Orient2d(eq, op, ep);
                    t = NextFlipTriangle(tcx, o, t, ot, p, op);
                    FlipEdgeEvent(tcx, ep, eq, t, p);
                }
            }
            else
            {
                TriangulationPoint newP = NextFlipPoint(ep, eq, ot, op);
                FlipScanEdgeEvent(tcx, ep, eq, t, ot, newP);
                EdgeEvent(tcx, ep, eq, t, p);
            }
        }

        /// <summary>
        /// Adds a triangle to the advancing front to fill a hole.
        /// </summary>
        /// <param name="tcx"></param>
        /// <param name="node">middle node, that is the bottom of the hole</param>
        private static void Fill(DTSweepContext tcx, AdvancingFrontNode node)
        {
            DelaunayTriangle triangle = new DelaunayTriangle(node.Prev.Point, node.Point, node.Next.Point);
            // TODO: should copy the cEdge value from neighbor triangles
            //       for now cEdge values are copied during the legalize
            triangle.MarkNeighbor(node.Prev.Triangle);
            triangle.MarkNeighbor(node.Triangle);
            tcx.Triangles.Add(triangle);

            // Update the advancing front
            node.Prev.Next = node.Next;
            node.Next.Prev = node.Prev;
            tcx.RemoveNode(node);

            // If it was legalized the triangle has already been mapped
            if (!Legalize(tcx, triangle))
            {
                tcx.MapTriangleToNodes(triangle);
            }
        }

        private static void EdgeEvent(DTSweepContext tcx, TriangulationPoint ep, TriangulationPoint eq, DelaunayTriangle triangle, TriangulationPoint point)
        {
            if (IsEdgeSideOfTriangle(triangle, ep, eq))
                return;

            TriangulationPoint p1 = triangle.PointCCW(point);
            Orientation o1 = TriangulationUtil.Orient2d(eq, p1, ep);
            if (o1 == Orientation.Collinear)
            {
                if (triangle.Contains(eq, p1))
                {
                    triangle.MarkConstrainedEdge(eq, p1);
                    // We are modifying the constraint maybe it would be better to
                    // not change the given constraint and just keep a variable for the new constraint
                    tcx.EdgeEvent.ConstrainedEdge.Q = p1;
                    triangle = triangle.NeighborAcross(point);
                    EdgeEvent(tcx, ep, p1, triangle, p1);
                }
                else
                {
                    throw new PointOnEdgeException("EdgeEvent - Point on constrained edge not supported yet");
                }
                return;
            }

            TriangulationPoint p2 = triangle.PointCW(point);
            Orientation o2 = TriangulationUtil.Orient2d(eq, p2, ep);
            if (o2 == Orientation.Collinear)
            {
                if (triangle.Contains(eq, p2))
                {
                    triangle.MarkConstrainedEdge(eq, p2);
                    // We are modifying the constraint maybe it would be better to
                    // not change the given constraint and just keep a variable for the new constraint
                    tcx.EdgeEvent.ConstrainedEdge.Q = p2;
                    triangle = triangle.NeighborAcross(point);
                    EdgeEvent(tcx, ep, p2, triangle, p2);
                }
                else
                {
                    throw new PointOnEdgeException("EdgeEvent - Point on constrained edge not supported yet");
                }
                return;
            }

            if (o1 == o2)
            {
                // Need to decide if we are rotating CW or CCW to get to a triangle
                // that will cross edge
                if (o1 == Orientation.CW)
                {
                    triangle = triangle.NeighborCCW(point);
                }
                else
                {
                    triangle = triangle.NeighborCW(point);
                }
                EdgeEvent(tcx, ep, eq, triangle, point);
            }
            else
            {
                // This triangle crosses constraint so lets flippin start!
                FlipEdgeEvent(tcx, ep, eq, triangle, point);
            }
        }

        /// <summary>
        /// Rotates a triangle pair one vertex CW
        ///       n2                    n2
        ///  P +-----+             P +-----+
        ///    | t  /|               |\  t |  
        ///    |   / |               | \   |
        ///  n1|  /  |n3           n1|  \  |n3
        ///    | /   |    after CW   |   \ |
        ///    |/ oT |               | oT \|
        ///    +-----+ oP            +-----+
        ///       n4                    n4
        /// </summary>
        private static void RotateTrianglePair(DelaunayTriangle t, TriangulationPoint p, DelaunayTriangle ot, TriangulationPoint op)
        {
            DelaunayTriangle n1 = t.NeighborCCW(p);
            DelaunayTriangle n2 = t.NeighborCW(p);
            DelaunayTriangle n3 = ot.NeighborCCW(op);
            DelaunayTriangle n4 = ot.NeighborCW(op);

            bool ce1 = t.GetConstrainedEdgeCCW(p);
            bool ce2 = t.GetConstrainedEdgeCW(p);
            bool ce3 = ot.GetConstrainedEdgeCCW(op);
            bool ce4 = ot.GetConstrainedEdgeCW(op);

            bool de1 = t.GetDelaunayEdgeCCW(p);
            bool de2 = t.GetDelaunayEdgeCW(p);
            bool de3 = ot.GetDelaunayEdgeCCW(op);
            bool de4 = ot.GetDelaunayEdgeCW(op);

            t.Legalize(p, op);
            ot.Legalize(op, p);

            // Remap dEdge
            ot.SetDelaunayEdgeCCW(p, de1);
            t.SetDelaunayEdgeCW(p, de2);
            t.SetDelaunayEdgeCCW(op, de3);
            ot.SetDelaunayEdgeCW(op, de4);

            // Remap cEdge
            ot.SetConstrainedEdgeCCW(p, ce1);
            t.SetConstrainedEdgeCW(p, ce2);
            t.SetConstrainedEdgeCCW(op, ce3);
            ot.SetConstrainedEdgeCW(op, ce4);

            // Remap neighbors
            // XXX: might optimize the markNeighbor by keeping track of
            //      what side should be assigned to what neighbor after the
            //      rotation. Now mark neighbor does lots of testing to find
            //      the right side.
            t.Neighbors.Clear();
            ot.Neighbors.Clear();
            if (n1 != null) ot.MarkNeighbor(n1);
            if (n2 != null) t.MarkNeighbor(n2);
            if (n3 != null) t.MarkNeighbor(n3);
            if (n4 != null) ot.MarkNeighbor(n4);
            t.MarkNeighbor(ot);
        }

        /// <summary>
        /// Creates a new front triangle and legalize it
        /// </summary>
        private static AdvancingFrontNode NewFrontTriangle( DTSweepContext tcx, TriangulationPoint point, AdvancingFrontNode node )
        {
            AdvancingFrontNode newNode;
            DelaunayTriangle triangle;

            triangle = new DelaunayTriangle(point, node.Point, node.Next.Point);
            triangle.MarkNeighbor(node.Triangle);
            tcx.Triangles.Add(triangle);

            newNode = new AdvancingFrontNode(point) {Next = node.Next, Prev = node};
            node.Next.Prev = newNode;
            node.Next = newNode;

            tcx.AddNode(newNode); // XXX: BST

            if (tcx.IsDebugEnabled) tcx.DTDebugContext.ActiveNode = newNode;

            if (!Legalize(tcx, triangle)) tcx.MapTriangleToNodes(triangle);

            return newNode;
        }

 /// <summary>
 /// When we need to traverse from one triangle to the next we need 
 /// the point in current triangle that is the opposite point to the next
 /// triangle. 
 /// </summary>
 private static TriangulationPoint NextFlipPoint(TriangulationPoint ep, TriangulationPoint eq, DelaunayTriangle ot, TriangulationPoint op)
 {
     Orientation o2d = TriangulationUtil.Orient2d(eq, op, ep);
     if (o2d == Orientation.CW)
     {
         // Right
         return ot.PointCCW(op);
     }
     else if (o2d == Orientation.CCW)
     {
         // Left
         return ot.PointCW(op);
     }
     else
     {
         // TODO: implement support for point on constraint edge
         throw new PointOnEdgeException("Point on constrained edge not supported yet");
     }
 }

        /// <summary>
        /// Returns true if triangle was legalized
        /// </summary>
        private static bool Legalize(DTSweepContext tcx, DelaunayTriangle t)
        {
            // To legalize a triangle we start by finding if any of the three edges
            // violate the Delaunay condition
            for (int i = 0; i < 3; i++)
            {
                // TODO: fix so that cEdge is always valid when creating new triangles then we can check it here
                //       instead of below with ot
                if (t.EdgeIsDelaunay[i])
                {
                    continue;
                }

                DelaunayTriangle ot = t.Neighbors[i];
                if (ot != null)
                {
                    TriangulationPoint p = t.Points[i];
                    TriangulationPoint op = ot.OppositePoint(t, p);
                    int oi = ot.IndexOf(op);
                    // If this is a Constrained Edge or a Delaunay Edge(only during recursive legalization)
                    // then we should not try to legalize
                    if (ot.EdgeIsConstrained[oi] || ot.EdgeIsDelaunay[oi])
                    {
                        t.EdgeIsConstrained[i] = ot.EdgeIsConstrained[oi];
                        // XXX: have no good way of setting this property when creating new triangles so lets set it here
                        continue;
                    }

                    bool inside = TriangulationUtil.SmartIncircle(p, t.PointCCW(p), t.PointCW(p), op);

                    if (inside)
                    {
                        // Lets mark this shared edge as Delaunay
                        t.EdgeIsDelaunay[i] = true;
                        ot.EdgeIsDelaunay[oi] = true;

                        // Lets rotate shared edge one vertex CW to legalize it
                        RotateTrianglePair(t, p, ot, op);

                        // We now got one valid Delaunay Edge shared by two triangles
                        // This gives us 4 new edges to check for Delaunay

                        // Make sure that triangle to node mapping is done only one time for a specific triangle
                        bool notLegalized = !Legalize(tcx, t);

                        if (notLegalized)
                        {
                            tcx.MapTriangleToNodes(t);
                        }
                        notLegalized = !Legalize(tcx, ot);
                        if (notLegalized)
                        {
                            tcx.MapTriangleToNodes(ot);
                        }

                        // Reset the Delaunay edges, since they only are valid Delaunay edges
                        // until we add a new triangle or point.
                        // XXX: need to think about this. Can these edges be tried after we
                        //      return to previous recursive level?
                        t.EdgeIsDelaunay[i] = false;
                        ot.EdgeIsDelaunay[oi] = false;

                        // If triangle have been legalized no need to check the other edges since
                        // the recursive legalization will handles those so we can end here.
                        return true;
                    }
                }
            }
            return false;
        }

 public void MeshClean(DelaunayTriangle triangle)
 {
     MeshCleanReq(triangle);
 }

 /// <summary>
 /// Try to map a node to all sides of this triangle that don't have 
 /// a neighbor.
 /// </summary>
 public void MapTriangleToNodes(DelaunayTriangle t)
 {
     AdvancingFrontNode n;
     for (int i = 0; i < 3; i++)
     {
         if (t.Neighbors[i] == null)
         {
             n = aFront.LocatePoint(t.PointCW(t.Points[i]));
             if (n != null)
             {
                 n.Triangle = t;
             }
         }
     }
 }

        private static void FlipEdgeEvent(DTSweepContext tcx, TriangulationPoint ep, TriangulationPoint eq,
                                          DelaunayTriangle t, TriangulationPoint p)
        {
            TriangulationPoint op, newP;
            DelaunayTriangle ot;
            bool inScanArea;

            ot = t.NeighborAcross(p);
            op = ot.OppositePoint(t, p);

            if (ot == null)
            {
                // If we want to integrate the fillEdgeEvent do it here
                // With current implementation we should never get here
                throw new InvalidOperationException("[BUG:FIXME] FLIP failed due to missing triangle");
            }

            inScanArea = TriangulationUtil.InScanArea(p, t.PointCCW(p), t.PointCW(p), op);
            if (inScanArea)
            {
                // Lets rotate shared edge one vertex CW
                RotateTrianglePair(t, p, ot, op);
                tcx.MapTriangleToNodes(t);
                tcx.MapTriangleToNodes(ot);

                if (p == eq && op == ep)
                {
                    if (eq == tcx.EdgeEvent.ConstrainedEdge.Q
                        && ep == tcx.EdgeEvent.ConstrainedEdge.P)
                    {
                        if (tcx.IsDebugEnabled)
                        {
            #if NETFX_CORE
                            Debug.WriteLine("[FLIP] - constrained edge done");
            #else
                            Console.WriteLine("[FLIP] - constrained edge done"); // TODO: remove
            #endif
                        }
                        t.MarkConstrainedEdge(ep, eq);
                        ot.MarkConstrainedEdge(ep, eq);
                        Legalize(tcx, t);
                        Legalize(tcx, ot);
                    }
                    else
                    {
                        if (tcx.IsDebugEnabled)
            #if NETFX_CORE
                          Debug.WriteLine("[FLIP] - subedge done"); // TODO: remove
            #else
                         Console.WriteLine("[FLIP] - subedge done"); // TODO: remove
            #endif
                        // XXX: I think one of the triangles should be legalized here?
                    }
                }
                else
                {
                    if (tcx.IsDebugEnabled)
            #if NETFX_CORE
                        Debug.WriteLine("[FLIP] - flipping and continuing with triangle still crossing edge"); // TODO: remove
            #else
                         Console.WriteLine("[FLIP] - flipping and continuing with triangle still crossing edge"); // TODO: remove
            #endif
                            // TODO: remove
                    Orientation o = TriangulationUtil.Orient2d(eq, op, ep);
                    t = NextFlipTriangle(tcx, o, t, ot, p, op);
                    FlipEdgeEvent(tcx, ep, eq, t, p);
                }
            }
            else
            {
                newP = NextFlipPoint(ep, eq, ot, op);
                FlipScanEdgeEvent(tcx, ep, eq, t, ot, newP);
                EdgeEvent(tcx, ep, eq, t, p);
            }
        }

 /// <summary>
 /// When we need to traverse from one triangle to the next we need 
 /// the point in current triangle that is the opposite point to the next
 /// triangle. 
 /// </summary>
 private static TriangulationPoint NextFlipPoint( TriangulationPoint ep, TriangulationPoint eq, DelaunayTriangle ot, TriangulationPoint op )
 {
     Orientation o2d = TriangulationUtil.Orient2d(eq, op, ep);
     switch ( o2d ) {
     case Orientation.CW: return ot.PointCCWFrom(op);
     case Orientation.CCW: return ot.PointCWFrom(op);
     case Orientation.Collinear:
         // TODO: implement support for point on constraint edge
         throw new PointOnEdgeException("Point on constrained edge not supported yet",eq,op,ep);
     default:
         throw new NotImplementedException("Orientation not handled");
     }
 }

        /// <summary>
        /// Scan part of the FlipScan algorithm<br>
        /// When a triangle pair isn't flippable we will scan for the next 
        /// point that is inside the flip triangle scan area. When found 
        /// we generate a new flipEdgeEvent
        /// </summary>
        /// <param name="tcx"></param>
        /// <param name="ep">last point on the edge we are traversing</param>
        /// <param name="eq">first point on the edge we are traversing</param>
        /// <param name="flipTriangle">the current triangle sharing the point eq with edge</param>
        /// <param name="t"></param>
        /// <param name="p"></param>
        private static void FlipScanEdgeEvent(DTSweepContext tcx, TriangulationPoint ep, TriangulationPoint eq, DelaunayTriangle flipTriangle, DelaunayTriangle t, TriangulationPoint p)
        {
            DelaunayTriangle ot = t.NeighborAcross(p);
            TriangulationPoint op = ot.OppositePoint(t, p);

            if (ot == null)
            {
                // If we want to integrate the fillEdgeEvent do it here
                // With current implementation we should never get here
                throw new Exception("[BUG:FIXME] FLIP failed due to missing triangle");
            }

            bool inScanArea = TriangulationUtil.InScanArea(eq, flipTriangle.PointCCW(eq), flipTriangle.PointCW(eq), op);
            if (inScanArea)
            {
                // flip with new edge op->eq
                FlipEdgeEvent(tcx, eq, op, ot, op);
                // TODO: Actually I just figured out that it should be possible to
                //       improve this by getting the next ot and op before the the above
                //       flip and continue the flipScanEdgeEvent here
                // set new ot and op here and loop back to inScanArea test
                // also need to set a new flipTriangle first
                // Turns out at first glance that this is somewhat complicated
                // so it will have to wait.
            }
            else
            {
                TriangulationPoint newP = NextFlipPoint(ep, eq, ot, op);
                FlipScanEdgeEvent(tcx, ep, eq, flipTriangle, ot, newP);
            }
        }

        public void CreateAdvancingFront()
        {
            AdvancingFrontNode head, tail, middle;
            // Initial triangle
            DelaunayTriangle iTriangle = new DelaunayTriangle(Points[0], Tail, Head);
            Triangles.Add(iTriangle);

            head = new AdvancingFrontNode(iTriangle.Points[1]);
            head.Triangle = iTriangle;
            middle = new AdvancingFrontNode(iTriangle.Points[0]);
            middle.Triangle = iTriangle;
            tail = new AdvancingFrontNode(iTriangle.Points[2]);

            aFront = new AdvancingFront(head, tail);
            aFront.AddNode(middle);

            // TODO: I think it would be more intuitive if head is middles next and not previous
            //       so swap head and tail
            aFront.Head.Next = middle;
            middle.Next = aFront.Tail;
            middle.Prev = aFront.Head;
            aFront.Tail.Prev = middle;
        }

 private static bool IsEdgeSideOfTriangle(DelaunayTriangle triangle, TriangulationPoint ep, TriangulationPoint eq)
 {
     int index = triangle.EdgeIndex(ep, eq);
     if (index != -1)
     {
         triangle.MarkConstrainedEdge(index);
         triangle = triangle.Neighbors[index];
         if (triangle != null)
         {
             triangle.MarkConstrainedEdge(ep, eq);
         }
         return true;
     }
     return false;
 }

        /// <summary>
        /// Creates a new front triangle and legalize it
        /// </summary>
        private static AdvancingFrontNode NewFrontTriangle(DTSweepContext tcx, TriangulationPoint point, AdvancingFrontNode node)
        {
            DelaunayTriangle triangle = new DelaunayTriangle(point, node.Point, node.Next.Point);
            triangle.MarkNeighbor(node.Triangle);
            tcx.Triangles.Add(triangle);

            AdvancingFrontNode newNode = new AdvancingFrontNode(point);
            newNode.Next = node.Next;
            newNode.Prev = node;
            node.Next.Prev = newNode;
            node.Next = newNode;

            tcx.AddNode(newNode); // XXX: BST

            if (!Legalize(tcx, triangle))
            {
                tcx.MapTriangleToNodes(triangle);
            }

            return newNode;
        }

 /// <summary>
 /// After a flip we have two triangles and know that only one will still be
 /// intersecting the edge. So decide which to contiune with and legalize the other
 /// </summary>
 /// <param name="tcx"></param>
 /// <param name="o">should be the result of an TriangulationUtil.orient2d( eq, op, ep )</param>
 /// <param name="t">triangle 1</param>
 /// <param name="ot">triangle 2</param>
 /// <param name="p">a point shared by both triangles</param>
 /// <param name="op">another point shared by both triangles</param>
 /// <returns>returns the triangle still intersecting the edge</returns>
 private static DelaunayTriangle NextFlipTriangle(DTSweepContext tcx, Orientation o, DelaunayTriangle t, DelaunayTriangle ot, TriangulationPoint p, TriangulationPoint op)
 {
     int edgeIndex;
     if (o == Orientation.CCW)
     {
         // ot is not crossing edge after flip
         edgeIndex = ot.EdgeIndex(p, op);
         ot.EdgeIsDelaunay[edgeIndex] = true;
         Legalize(tcx, ot);
         ot.EdgeIsDelaunay.Clear();
         return t;
     }
     // t is not crossing edge after flip
     edgeIndex = t.EdgeIndex(p, op);
     t.EdgeIsDelaunay[edgeIndex] = true;
     Legalize(tcx, t);
     t.EdgeIsDelaunay.Clear();
     return ot;
 }

        private static void EdgeEvent( DTSweepContext tcx, TriangulationPoint ep, TriangulationPoint eq, DelaunayTriangle triangle, TriangulationPoint point )
        {
            TriangulationPoint p1, p2;

            if (tcx.IsDebugEnabled) tcx.DTDebugContext.PrimaryTriangle=triangle;

            if (IsEdgeSideOfTriangle(triangle, ep, eq)) return;

            p1 = triangle.PointCCWFrom(point);
            Orientation o1 = TriangulationUtil.Orient2d(eq, p1, ep);
            if (o1 == Orientation.Collinear) {
                // TODO: Split edge in two
                ////            splitEdge( ep, eq, p1 );
                //            edgeEvent( tcx, p1, eq, triangle, point );
                //            edgeEvent( tcx, ep, p1, triangle, p1 );
                //            return;
                throw new PointOnEdgeException("EdgeEvent - Point on constrained edge not supported yet",eq,p1,ep);
            }

            p2 = triangle.PointCWFrom(point);
            Orientation o2 = TriangulationUtil.Orient2d(eq, p2, ep);
            if (o2 == Orientation.Collinear) {
                // TODO: Split edge in two
                //            edgeEvent( tcx, p2, eq, triangle, point );
                //            edgeEvent( tcx, ep, p2, triangle, p2 );
                //            return;
                throw new PointOnEdgeException("EdgeEvent - Point on constrained edge not supported yet",eq,p2,ep);
            }

            if (o1 == o2) {
                // Need to decide if we are rotating CW or CCW to get to a triangle
                // that will cross edge
                if (o1 == Orientation.CW) {
                    triangle = triangle.NeighborCCWFrom(point);
                } else {
                    triangle = triangle.NeighborCWFrom(point);
                }
                EdgeEvent(tcx, ep, eq, triangle, point);
            } else {
                // This triangle crosses constraint so lets flippin start!
                FlipEdgeEvent(tcx, ep, eq, triangle, point);
            }
        }

		public override void Clear()
		{
			this.PrimaryTriangle = null;
			this.SecondaryTriangle = null;
			this.ActivePoint = null;
			this.ActiveNode = null;
			this.ActiveConstraint = null;
		}