C# Poly2Tri.DTSweepContext類代碼示例

        /// <summary>
        /// Triangulate simple polygon with holes
        /// </summary>
        public static void Triangulate(DTSweepContext tcx)
        {
            tcx.CreateAdvancingFront();

            Sweep(tcx);

            FixupConstrainedEdges(tcx);

            // Finalize triangulation
            if (tcx.TriangulationMode == TriangulationMode.Polygon)
            {
                FinalizationPolygon(tcx);
            }
            else 
            {
                FinalizationConvexHull(tcx);
                if (tcx.TriangulationMode == TriangulationMode.Constrained)
                {
                    // work in progress.  When it's done, call FinalizationConstraints INSTEAD of tcx.FinalizeTriangulation
                    //FinalizationConstraints(tcx);

                    tcx.FinalizeTriangulation();
                }
                else
                {
                    tcx.FinalizeTriangulation();
                }
            }

            tcx.Done();
        }

		/// <summary>
		/// Triangulate simple polygon with holes
		/// </summary>
		public static void Triangulate(DTSweepContext tcx)
		{
			tcx.CreateAdvancingFront();

			Sweep(tcx);

			// TODO: remove temporary
			// Check if the sweep algorithm is legalize robust
			// By doing a legalize on all triangles and see if anything happens
			// we know if the sweep algorithm missed some legalizations
			//        Console.WriteLine("============================");
			//        foreach ( DelaunayTriangle t in tcx.Triangles )
			//        {
			//            if( Legalize( tcx, t ) )
			//            {
			//                tcx.getDebugContext().setPrimaryTriangle( t );
			//                Console.WriteLine("[FIX] Triangle needed legalization after sweep");
			//            }
			//        }

			// Finalize triangulation
			if (tcx.TriangulationMode == TriangulationMode.Polygon)
			{
				FinalizationPolygon(tcx);
			}
			else
			{
				FinalizationConvexHull(tcx);
			}

			tcx.Done();
		}

    private void CreateMesh() {
        Sprite sprite = spriteRenderer.sprite;

        Rect bounds = GetBounds(polygon);

        DTSweepContext ctx = new DTSweepContext();
        Polygon poly = new Polygon(polygon.Select(p => new PolygonPoint(p.x, p.y)));

        ctx.PrepareTriangulation(poly);
        DTSweep.Triangulate(ctx);

        List<Vector2> verts = new List<Vector2>();
        List<int> tris = new List<int>();

        foreach (DelaunayTriangle tri in poly.Triangles) {
            verts.AddRange(tri.Points.Reverse().Select(p => new Vector2(p.Xf, p.Yf)));
            for (int i = 0; i < 3; i++) {
                tris.Add(tris.Count);
            }
        }

        Mesh mesh = new Mesh();
        mesh.vertices = verts.Select(x => (Vector3)x).ToArray();
        mesh.triangles = tris.ToArray();

        List<Vector2> uv = new List<Vector2>();

        Vector3 lower = new Vector3(bounds.x, bounds.y);
        Vector3 size = new Vector3(bounds.xMax, bounds.yMax) - lower;

        Rect uv_bounds = new Rect(sprite.rect.x / sprite.texture.width, sprite.rect.y / sprite.texture.height, sprite.rect.width / sprite.texture.width, sprite.rect.height / sprite.texture.height);

        float scalex = sprite.bounds.size.x / bounds.width;
        float scaley = sprite.bounds.size.y / bounds.height;

        Vector3[] scaled = mesh.vertices;

        for (int i = 0; i < mesh.vertices.Length; i++) {
            Vector3 v = scaled[i];
            Vector3 rel = v - lower;
            uv.Add(new Vector2(rel.x / size.x * uv_bounds.width, rel.y / size.y * uv_bounds.height) + new Vector2(uv_bounds.x, uv_bounds.y));

            scaled[i] = new Vector3(v.x * scalex, v.y * scaley, v.z) - ((Vector3)bounds.center * scalex) + sprite.bounds.center;
        }

        mesh.vertices = scaled;
        mesh.uv = uv.ToArray();
        mesh.RecalculateNormals();
        mesh.RecalculateBounds();
        mesh.Optimize();

        //GameObject go = new GameObject();
        //MeshFilter mf = go.AddComponent<MeshFilter>();
        //mf.sharedMesh = mesh;
        //MeshRenderer mr = go.AddComponent<MeshRenderer>();
        //mr.sharedMaterial = spriteRenderer.sharedMaterial;

        ScriptableObjectUtility.CreateAsset(mesh);
    }

    /// <summary>
    /// Create a Mesh from a given Polygon.
    /// </summary>
    /// <returns>The freshly minted mesh.</returns>
    /// <param name="polygon">Polygon you want to triangulate.</param>
    public static Mesh CreateMesh(Polygon polygon)
    {
        // Ensure we have the rotation properly calculated
        if (polygon.rotation == Quaternion.identity) polygon.CalcRotation();

        // Rotate 1 point and note where it ends up in Z
        float z = (polygon.rotation * polygon.outside[0]).z;

        // Convert the outside points (throwing out Z at this point)
        Poly2Tri.Polygon poly = new Poly2Tri.Polygon(ConvertPoints(polygon.outside, polygon.rotation));

        // Convert each of the holes
        foreach (List<Vector3> hole in polygon.holes) {
            poly.AddHole(new Poly2Tri.Polygon(ConvertPoints(hole, polygon.rotation)));
        }

        // Triangulate it!  Note that this may throw an exception if the data is bogus.
        DTSweepContext tcx = new DTSweepContext();
        tcx.PrepareTriangulation(poly);
        DTSweep.Triangulate(tcx);
        tcx = null;

        // Create the Vector3 vertices (undoing the rotation),
        // and also build a map of vertex codes to indices
        Quaternion invRot = Quaternion.Inverse(polygon.rotation);
        Dictionary<uint, int> codeToIndex = new Dictionary<uint, int>();
        List<Vector3> vertexList = new List<Vector3>();
        foreach (DelaunayTriangle t in poly.Triangles) {
            foreach (var p in t.Points) {
                if (codeToIndex.ContainsKey(p.VertexCode)) continue;
                codeToIndex[p.VertexCode] = vertexList.Count;
                Vector3 pos = new Vector3(p.Xf, p.Yf, z);	// (restore the Z we saved earlier)
                vertexList.Add(invRot * pos);
            }
        }

        // Create the indices array
        int[] indices = new int[poly.Triangles.Count * 3];
        {
            int i = 0;
            foreach (DelaunayTriangle t in poly.Triangles) {
                indices[i++] = codeToIndex[t.Points[0].VertexCode];
                indices[i++] = codeToIndex[t.Points[1].VertexCode];
                indices[i++] = codeToIndex[t.Points[2].VertexCode];
            }
        }

        // Create the UV list, by looking up the closest point for each in our poly
        Mesh msh = new Mesh();
        msh.vertices = vertexList.ToArray();
        Vector2[] uvs = new Vector2[msh.vertices.Length];
        for (int i=0; i < uvs.Length; i++) {
            uvs[i] = new Vector2(msh.vertices[i].x, msh.vertices[i].y);
        }
        msh.uv = uvs;
        /*if (polygon.OutsideUVs != null) {
            uv = new Vector2[vertexList.Count];
            for (int i=0; i<vertexList.Count; i++) {
                uv[i] = polygon.ClosestUV(vertexList[i]);
            }
        }*/

        // Create the mesh

        msh.triangles = indices;
        msh.RecalculateNormals();
        msh.RecalculateBounds();
        return msh;
    }

		/// <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) continue;

				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;
				}

				if (!TriangulationUtil.SmartIncircle(p, t.PointCCWFrom(p), t.PointCWFrom(p), op)) continue;

				// 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
				if (!Legalize(tcx, t)) tcx.MapTriangleToNodes(t);
				if (!Legalize(tcx, ot)) 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;
		}

		private static bool IsShallow(DTSweepContext tcx, AdvancingFrontNode node)
		{
			double height;

			if (tcx.Basin.leftHighest)
			{
				height = tcx.Basin.leftNode.Point.Y - node.Point.Y;
			}
			else
			{
				height = tcx.Basin.rightNode.Point.Y - node.Point.Y;
			}
			if (tcx.Basin.width > height)
			{
				return true;
			}
			return false;
		}

		/// <summary>
		/// Fills a basin that has formed on the Advancing Front to the right
		/// of given node.<br/>
		/// First we decide a left,bottom and right node that forms the
		/// boundaries of the basin. Then we do a reqursive fill.
		/// </summary>
		/// <param name="tcx"></param>
		/// <param name="node">starting node, this or next node will be left node</param>
		private static void FillBasin(DTSweepContext tcx, AdvancingFrontNode node)
		{
			if (TriangulationUtil.Orient2d(node.Point, node.Next.Point, node.Next.Next.Point) == Orientation.CCW)
			{
				// tcx.basin.leftNode = node.next.next;
				tcx.Basin.leftNode = node;
			}
			else
			{
				tcx.Basin.leftNode = node.Next;
			}

			// Find the bottom and right node
			tcx.Basin.bottomNode = tcx.Basin.leftNode;
			while (tcx.Basin.bottomNode.HasNext && tcx.Basin.bottomNode.Point.Y >= tcx.Basin.bottomNode.Next.Point.Y) tcx.Basin.bottomNode = tcx.Basin.bottomNode.Next;

			if (tcx.Basin.bottomNode == tcx.Basin.leftNode) return; // No valid basin

			tcx.Basin.rightNode = tcx.Basin.bottomNode;
			while (tcx.Basin.rightNode.HasNext && tcx.Basin.rightNode.Point.Y < tcx.Basin.rightNode.Next.Point.Y) tcx.Basin.rightNode = tcx.Basin.rightNode.Next;

			if (tcx.Basin.rightNode == tcx.Basin.bottomNode) return; // No valid basins

			tcx.Basin.width = tcx.Basin.rightNode.Point.X - tcx.Basin.leftNode.Point.X;
			tcx.Basin.leftHighest = tcx.Basin.leftNode.Point.Y > tcx.Basin.rightNode.Point.Y;

			FillBasinReq(tcx, tcx.Basin.bottomNode);
		}

		/// <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;
			TriangulationPoint op, newP;
			bool inScanArea;

			ot = t.NeighborAcrossFrom(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 Exception("[BUG:FIXME] FLIP failed due to missing triangle");
			}

			if (tcx.IsDebugEnabled)
			{
				Console.WriteLine("[FLIP:SCAN] - scan next point"); // TODO: remove
				tcx.DTDebugContext.PrimaryTriangle = t;
				tcx.DTDebugContext.SecondaryTriangle = ot;
			}

			inScanArea = TriangulationUtil.InScanArea(eq, flipTriangle.PointCCWFrom(eq), flipTriangle.PointCWFrom(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
			{
				newP = NextFlipPoint(ep, eq, ot, op);
				FlipScanEdgeEvent(tcx, ep, eq, flipTriangle, ot, newP);
			}
		}

		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);
			}
		}

		/// <summary>
		/// We will traverse the entire advancing front and fill it to form a convex hull.
		/// </summary>
		private static void TurnAdvancingFrontConvex(DTSweepContext tcx, AdvancingFrontNode b, AdvancingFrontNode c)
		{
			AdvancingFrontNode first = b;
			while (c != tcx.Front.Tail)
			{
				if (tcx.IsDebugEnabled) tcx.DTDebugContext.ActiveNode = c;

				if (TriangulationUtil.Orient2d(b.Point, c.Point, c.Next.Point) == Orientation.CCW)
				{
					// [b,c,d] Concave - fill around c
					Fill(tcx, c);
					c = c.Next;
				}
				else
				{
					// [b,c,d] Convex
					if (b != first && TriangulationUtil.Orient2d(b.Prev.Point, b.Point, c.Point) == Orientation.CCW)
					{
						// [a,b,c] Concave - fill around b
						Fill(tcx, b);
						b = b.Prev;
					}
					else
					{
						// [a,b,c] Convex - nothing to fill
						b = c;
						c = c.Next;
					}
				}
			}
		}

		/// <summary>
		/// If this is a Delaunay Triangulation of a pointset we need to fill so the triangle mesh gets a ConvexHull
		/// </summary>
		private static void FinalizationConvexHull(DTSweepContext tcx)
		{
			AdvancingFrontNode n1, n2, n3;
			DelaunayTriangle t1;
			TriangulationPoint first, p1;

			n1 = tcx.Front.Head.Next;
			n2 = n1.Next;
			n3 = n2.Next;
			first = n1.Point;

			TurnAdvancingFrontConvex(tcx, n1, n2);

			n1 = tcx.Front.Tail.Prev;
			if (n1.Triangle.Contains(n1.Next.Point) && n1.Triangle.Contains(n1.Prev.Point))
			{
				t1 = n1.Triangle.NeighborAcrossFrom(n1.Point);
				RotateTrianglePair(n1.Triangle, n1.Point, t1, t1.OppositePoint(n1.Triangle, n1.Point));
				tcx.MapTriangleToNodes(n1.Triangle);
				tcx.MapTriangleToNodes(t1);
			}
			n1 = tcx.Front.Head.Next;
			if (n1.Triangle.Contains(n1.Prev.Point) && n1.Triangle.Contains(n1.Next.Point))
			{
				t1 = n1.Triangle.NeighborAcrossFrom(n1.Point);
				RotateTrianglePair(n1.Triangle, n1.Point, t1, t1.OppositePoint(n1.Triangle, n1.Point));
				tcx.MapTriangleToNodes(n1.Triangle);
				tcx.MapTriangleToNodes(t1);
			}

			// TODO: implement ConvexHull for lower right and left boundary
			// Lower right boundary
			first = tcx.Front.Head.Point;
			n2 = tcx.Front.Tail.Prev;
			t1 = n2.Triangle;
			p1 = n2.Point;
			do
			{
				tcx.RemoveFromList(t1);
				p1 = t1.PointCCWFrom(p1);
				if (p1 == first) break;
				t1 = t1.NeighborCCWFrom(p1);
			} while (true);

			// Lower left boundary
			first = tcx.Front.Head.Next.Point;
			p1 = t1.PointCWFrom(tcx.Front.Head.Point);
			t1 = t1.NeighborCWFrom(tcx.Front.Head.Point);
			do
			{
				tcx.RemoveFromList(t1);
				p1 = t1.PointCCWFrom(p1);
				t1 = t1.NeighborCCWFrom(p1);
			} while (p1 != first);

			tcx.FinalizeTriangulation();
		}

        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)
            {
                if (triangle.Contains(eq) && triangle.Contains(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.NeighborAcrossFrom(point);
                    EdgeEvent(tcx, ep, p1, triangle, p1);
                }
                else
                {
                    throw new PointOnEdgeException("EdgeEvent - Point on constrained edge not supported yet", ep, eq, p1);
                }
                if (tcx.IsDebugEnabled)
                {
                    Console.WriteLine("EdgeEvent - Point on constrained edge");
                }

                return;
            }

            p2 = triangle.PointCWFrom(point);
            Orientation o2 = TriangulationUtil.Orient2d(eq, p2, ep);
            if (o2 == Orientation.Collinear)
            {
                if (triangle.Contains(eq) && triangle.Contains(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.NeighborAcrossFrom(point);
                    EdgeEvent(tcx, ep, p2, triangle, p2);
                }
                else
                {
                    throw new PointOnEdgeException("EdgeEvent - Point on constrained edge not supported yet", ep, eq, p2);
                }
                if (tcx.IsDebugEnabled)
                {
                    Console.WriteLine("EdgeEvent - Point on constrained edge");
                }

                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.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);
            }
        }

        /// <summary>
        /// NOTE: WORK IN PROGRESS - for now this will just clean out all triangles from
        /// inside the outermost holes without paying attention to holes within holes..
        /// hence the work in progress :)
        /// 
        /// Removes triangles inside "holes" (that are not inside of other holes already)
        /// 
        /// In the example below, assume that triangle ABC is a user-defined "hole".  Thus
        /// any triangles inside it (that aren't inside yet another user-defined hole inside
        /// triangle ABC) should get removed.  In this case, since there are no user-defined
        /// holes inside ABC, we would remove triangles ADE, BCE, and CDE.  We would also 
        /// need to combine the appropriate edges so that we end up with just triangle ABC
        ///
        ///          E
        /// A +------+-----+ B              A +-----------+ B
        ///    \    /|    /                    \         /
        ///     \  / |   /                      \       /
        ///    D +   |  /        ======>         \     /
        ///       \  | /                          \   /
        ///        \ |/                            \ /
        ///          +                              +
        ///          C                              C
        ///          
        /// </summary>
        private static void FinalizationConstraints(DTSweepContext tcx)
        {
            // Get an Internal triangle to start with
            DelaunayTriangle t = tcx.Front.Head.Triangle;
            TriangulationPoint p = tcx.Front.Head.Point;
            while (!t.GetConstrainedEdgeCW(p))
            {
                DelaunayTriangle tTmp = t.NeighborCCWFrom(p);
                if (tTmp == null)
                {
                    break;
                }
                t = tTmp;
            }

            // Collect interior triangles constrained by edges
            tcx.MeshClean(t);
        }

        /// <summary>
        /// If this is a Delaunay Triangulation of a pointset we need to fill so the triangle mesh gets a ConvexHull 
        /// </summary>
        private static void FinalizationConvexHull(DTSweepContext tcx)
        {
            AdvancingFrontNode n1, n2;
            DelaunayTriangle t1, t2;
            TriangulationPoint first, p1;

            n1 = tcx.Front.Head.Next;
            n2 = n1.Next;
            first = n1.Point;

            TurnAdvancingFrontConvex(tcx, n1, n2);

            // Lets remove triangles connected to the two "algorithm" points
            // XXX: When the first three nodes are points in a triangle we need to do a flip before
            // removing triangles or we will lose a valid triangle.
            // Same for last three nodes!
            // !!! If I implement ConvexHull for lower right and left boundary this fix should not be
            // needed and the removed triangles will be added again by default

            n1 = tcx.Front.Tail.Prev;
            if (n1.Triangle.Contains(n1.Next.Point) && n1.Triangle.Contains(n1.Prev.Point))
            {
                t1 = n1.Triangle.NeighborAcrossFrom(n1.Point);
                RotateTrianglePair(n1.Triangle, n1.Point, t1, t1.OppositePoint(n1.Triangle, n1.Point));
                tcx.MapTriangleToNodes(n1.Triangle);
                tcx.MapTriangleToNodes(t1);
            }
            n1 = tcx.Front.Head.Next;
            if (n1.Triangle.Contains(n1.Prev.Point) && n1.Triangle.Contains(n1.Next.Point))
            {
                t1 = n1.Triangle.NeighborAcrossFrom(n1.Point);
                RotateTrianglePair(n1.Triangle, n1.Point, t1, t1.OppositePoint(n1.Triangle, n1.Point));
                tcx.MapTriangleToNodes(n1.Triangle);
                tcx.MapTriangleToNodes(t1);
            }

            // Lower right boundary 
            first = tcx.Front.Head.Point;
            n2 = tcx.Front.Tail.Prev;
            t1 = n2.Triangle;
            p1 = n2.Point;
            n2.Triangle = null;
            do
            {
                tcx.RemoveFromList(t1);
                p1 = t1.PointCCWFrom(p1);
                if (p1 == first)
                {
                    break;
                }
                t2 = t1.NeighborCCWFrom(p1);
                t1.Clear();
                t1 = t2;
            } while (true);

            // Lower left boundary
            first = tcx.Front.Head.Next.Point;
            p1 = t1.PointCWFrom(tcx.Front.Head.Point);
            t2 = t1.NeighborCWFrom(tcx.Front.Head.Point);
            t1.Clear();
            t1 = t2;
            while (p1 != first)
            {
                tcx.RemoveFromList(t1);
                p1 = t1.PointCCWFrom(p1);
                t2 = t1.NeighborCCWFrom(p1);
                t1.Clear();
                t1 = t2;
            }

            // Remove current head and tail node now that we have removed all triangles attached
            // to them. Then set new head and tail node points
            tcx.Front.Head = tcx.Front.Head.Next;
            tcx.Front.Head.Prev = null;
            tcx.Front.Tail = tcx.Front.Tail.Prev;
            tcx.Front.Tail.Next = null; 
        }

 private static void FixupConstrainedEdges(DTSweepContext tcx)
 {
     foreach(DelaunayTriangle t in tcx.Triangles)
     {
         for (int i = 0; i < 3; ++i)
         {
             bool isConstrained = t.GetConstrainedEdgeCCW(t.Points[i]);
             if (!isConstrained)
             {
                 DTSweepConstraint edge = null;
                 bool hasConstrainedEdge = t.GetEdgeCCW(t.Points[i], out edge);
                 if (hasConstrainedEdge)
                 {
                     t.MarkConstrainedEdge((i + 2) % 3);
                     //t.MarkConstrainedEdgeCCW(t.Points[i]);
                 }
             }
         }
     }
 }