diff --git a/Program.cs b/Program.cs
index a5906c4..163fa86 100644
--- a/Program.cs
+++ b/Program.cs
@@ -4,6 +4,7 @@ using System.Linq;
 using System.Text;
 using TransmissionGraphic.Graphic;
 using TransmissionGraphic.Type3D;
+using MathNet.Numerics.LinearAlgebra;
 
 namespace TransmissionGraphic
 {
@@ -13,8 +14,13 @@ namespace TransmissionGraphic
         {
             Canvas canvas = new Canvas();
             canvas.init_canvas();
-            Line line = new Line(canvas,new TGVector3D(10, 20, 10), new TGVector3D(400, 25, 35), 0.32e-3, 400);
+            Line line = new Line(new TGVector3D(10, 20, 10), new TGVector3D(400, 25, 35), 0.32e-3, 400);
             canvas.draw(line.curve());
+            Tuple<Matrix<double>, double> sag_and_value = line.sag();
+            Matrix<double> sag_points = sag_and_value.Item1;
+            double sag_value = sag_and_value.Item2;
+            canvas.draw(sag_points);
+            canvas.draw(line.swing(30 / 180 * Math.PI));
             canvas.save("abc.dxf");
             
         }
diff --git a/src/Graphic/Line.cs b/src/Graphic/Line.cs
index 8513956..1ab7b67 100644
--- a/src/Graphic/Line.cs
+++ b/src/Graphic/Line.cs
@@ -18,8 +18,7 @@ namespace TransmissionGraphic.Graphic
         private double _span;
         private Matrix<double> _points;
         private Rotation _rotation;
-        private Canvas _canvas;
-        public Line(Canvas canvas, TGVector3D start_p, TGVector3D end_p, double tension_k, int n_point)
+        public Line(TGVector3D start_p, TGVector3D end_p, double tension_k, int n_point)
         {
             this._start_p = start_p;
             this._end_p = end_p;
@@ -28,11 +27,10 @@ namespace TransmissionGraphic.Graphic
             this._span = 0;
             this._points = null;
             this._rotation = null;
-            this._canvas = canvas;
 
         }
 
-        public Matrix<double> curve(bool draw = false)
+        public Matrix<double> curve()
         {
             if (this._points != null)
             {
@@ -53,7 +51,7 @@ namespace TransmissionGraphic.Graphic
             double span = xy_project.abs();
             this._span = span;
             Vector<double> span_l = Vector<double>.Build.DenseOfArray(Generate.LinearSpaced(n_point, 0, span));  // 档距
-            Vector<double> z_points = start_p.z + span_l * height / span - span_l.PointwiseMultiply(span - span_l)* tension_k / Math.Cos(Math.Atan(height / span));
+            Vector<double> z_points = start_p.z + span_l * height / span - span_l.PointwiseMultiply(span - span_l) * tension_k / Math.Cos(Math.Atan(height / span));
             double[,] p_points = new double[n_point, 3];
             for (int foo = 0; foo < n_point; foo++)
             {
@@ -66,7 +64,51 @@ namespace TransmissionGraphic.Graphic
 
             this._rotation = rotation;
             Matrix<double> points = rotation.rotate(Matrix<double>.Build.DenseOfArray(p_points));
+            this._points = points;
             return points;
         }
+
+        public Matrix<double> swing(double angel)
+        {
+            if (this._points == null)
+            {
+                this.curve();
+            }
+            Matrix<double> points = this._points;
+            TGVector3D start_p = this._start_p;
+            TGVector3D end_p = this._end_p;
+            Rotation swing_rotation = new Rotation(
+                angel,
+                new TGVector3D(start_p.x, start_p.y, start_p.z),
+                new TGVector3D(end_p.x, end_p.y, end_p.z)
+            );
+            Matrix<double> swing_point = swing_rotation.rotate(points);
+            return swing_point;
+        }
+
+        public Tuple<Matrix<double>, double> sag()
+        {
+            TGVector3D start_p = this._start_p;
+            TGVector3D end_p = this._end_p;
+            double span = this._span;
+            double height = end_p.z - start_p.z;
+            double middle_span = span / 2;
+            Matrix<double> points = this._points;
+            int n_point = this._n_point;
+            double middle_z = points.At(Convert.ToInt32(n_point / 2), 2);
+            Rotation rotation = this._rotation;
+            Matrix<double> p_sag_points = Matrix<double>.Build.DenseOfArray(new double[,] {
+                {start_p.x, start_p.y, start_p.z},
+                {                middle_span + start_p.x,                start_p.y,                start_p.z + middle_span * height / span                },
+                {middle_span + start_p.x, start_p.y, middle_z},
+                {                middle_span + start_p.x,                start_p.y,                start_p.z + middle_span * height / span                },
+                {start_p.x + span, start_p.y, end_p.z},
+            });//  旋转前的值
+            Matrix<double> sag_points = rotation.rotate(p_sag_points);
+            double sag_value = start_p.z + middle_span * height / span - middle_z;
+            return new Tuple<Matrix<double>, double>(sag_points, sag_value);
+        }
+
+
     }
 }