C# Poly2Tri.DelaunayTriangle类代码示例

 public static Vector2 GetCircumcenter(DelaunayTriangle triangle)
 {
     Vector2 a = triangle.Points[0].ToVector2();
     Vector2 b = triangle.Points[1].ToVector2();
     Vector2 c = triangle.Points[2].ToVector2();
     return GetCircumcenter(a, b, c);
 }

 public static float GetCircumradius(DelaunayTriangle triangle)
 {
     Vector2 a = triangle.Points[0].ToVector2();
     Vector2 b = triangle.Points[1].ToVector2();
     Vector2 c = triangle.Points[2].ToVector2();
     return GetCircumradius(a, b, c);
 }

		/// <summary>
		/// Exhaustive search to update neighbor pointers
		/// </summary>
		public void MarkNeighbor( DelaunayTriangle t ) {
			// Points of this triangle also belonging to t
			bool a = t.Contains(Points[0]);
			bool b = t.Contains(Points[1]);
			bool c = t.Contains(Points[2]);

			if      (b&&c) { Neighbors[0]=t; t.MarkNeighbor(Points[1],Points[2],this); }
			else if (a&&c) { Neighbors[1]=t; t.MarkNeighbor(Points[0],Points[2],this); }
			else if (a&&b) { Neighbors[2]=t; t.MarkNeighbor(Points[0],Points[1],this); }
			else throw new Exception( "Failed to mark neighbor, doesn't share an edge!");
		}

 /// <summary>
 /// Update neighbor pointers
 /// </summary>
 /// <param name="p1">Point 1 of the shared edge</param>
 /// <param name="p2">Point 2 of the shared edge</param>
 /// <param name="t">This triangle's new neighbor</param>
 private void MarkNeighbor(TriangulationPoint p1, TriangulationPoint p2, DelaunayTriangle t)
 {
     int i = EdgeIndex(p1, p2);
     if (i == -1)
     {
         throw new Exception("Error marking neighbors -- t doesn't contain edge p1-p2!");
     }
     Neighbors[i] = t;
 }

 /// <param name="t">Opposite triangle</param>
 /// <param name="p">The point in t that isn't shared between the triangles</param>
 public TriangulationPoint OppositePoint(DelaunayTriangle t, TriangulationPoint p)
 {
     Debug.Assert(t != this, "self-pointer error");
     return PointCWFrom(t.PointCWFrom(p));
 }

 private static Rectangle GetRectangle(DelaunayTriangle triangle)
 {
     return GetBoundingRectangle(triangle.Points);
 }

		/// <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;
		}

		/// <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);
			}
		}

		/// <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");
			}
		}

		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 AddTriangle(DelaunayTriangle t)
 {
     Triangles.Add(t);
 }

 private static void DrawDelaunayCircumcircles(DelaunayTriangle triangle, Vector2 circumcenter, Graphics graphics)
 {
     float circumradius = VoronoiHelper.GetCircumradius(triangle);
     graphics.DrawEllipse(Pens.Green,
         circumcenter.X - circumradius, circumcenter.Y - circumradius,
         2 * circumradius, 2 * circumradius);
 }

        public static IList<DelaunayTriangle> GetSurroundingTriangles(
            DelaunayTriangle triangle,
            TriangulationPoint point)
        {
            IList<DelaunayTriangle> surroundingTriangles = new List<DelaunayTriangle>();

            DelaunayTriangle startTriangle = triangle;
            DelaunayTriangle currentTriangle = triangle;
            do
            {
                surroundingTriangles.Add(currentTriangle);
                currentTriangle = currentTriangle.NeighborCWFrom(point);
            } while ((currentTriangle != null) && (currentTriangle != startTriangle));

            return surroundingTriangles;
        }

 private IReadOnlyList<TriangulationPoint> UnpackTriangle(DelaunayTriangle t)
 {
     return new[] {
     t.Points[0],
     t.Points[1],
     t.Points[2]
      };
 }

		/// <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);
			newNode.Next = node.Next;
			newNode.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;
		}