(SOLVED)RaycastHit.triangleIndex didn't work after I modified the mesh triangles

want to add a vertex to a mesh ,it's doing well when first time
but after that RaycastHit.triangleIndex seems didn't give a correct value

I

if mouse on the triangle , should draw it


when I added a vertex on mouse position ,it didn't draw the correct triangle

Code (CSharp):

1. void Update()
2.     {
3.         RaycastHit hit = ShootRay();
4.         if (null == hit.collider) return;
5.  
6.         MeshCollider meshCollider = hit.collider as MeshCollider;
7.         if (meshCollider == null || meshCollider.sharedMesh == null)
8.             return;
9.  
10.         Mesh mesh = meshCollider.GetComponent<MeshFilter>().mesh;
11.         Vector3[] vertices = mesh.vertices;
12.         int[] triangles = mesh.triangles;
13.         var tri = GetTriangle( triangles, vertices, hit.triangleIndex);
14.         Vector3 p0 = tri.p1;
15.         Vector3 p1 = tri.p2;
16.         Vector3 p2 = tri.p3;
17.         Debug.LogFormat("[{0},{1},{2}]", tri.i1, tri.i2, tri.i3);
18.         Transform hitTransform = hit.collider.transform;
19.         p0 = hitTransform.TransformPoint(p0);
20.         p1 = hitTransform.TransformPoint(p1);
21.         p2 = hitTransform.TransformPoint(p2);
22.         Debug.DrawLine(p0, p1,Color.red);
23.         Debug.DrawLine(p1, p2,Color.red);
24.         Debug.DrawLine(p2, p0, Color.red);
25.  
26.         if (Input.GetMouseButtonDown(0))
27.             AddVertexAt(hit.point,mesh,hit.triangleIndex);
28.     }
29.  
30.     List<Vector3> vertexBuffer = new List<Vector3>();
31.     List<int> trianglesBuffer = new List<int>();
32.  
33.     void AddVertexAt(Vector3 point,Mesh mesh,int triangleIndex)
34.     {
35.         int baseIndex = triangleIndex * 3;
36.  
37.         mesh.GetVertices(vertexBuffer);
38.         trianglesBuffer.Clear();
39.         trianglesBuffer.AddRange( mesh.GetTriangles(0));
40.         vertexBuffer.Add(point);
41.    
42.         int newPointIndex = vertexBuffer.Count - 1;
43.  
44.         Triangle tri = GetTriangle(trianglesBuffer.ToArray(), vertexBuffer.ToArray(), triangleIndex);
45.  
46.         for (int i = 0; i < 3; i++)
47.             trianglesBuffer.RemoveAt(baseIndex);
48.  
49.         trianglesBuffer.AddRange(new int[] { tri.i1, tri.i2, newPointIndex  });
50.         trianglesBuffer.AddRange(new int[] { tri.i1, newPointIndex, tri.i3 });
51.         trianglesBuffer.AddRange(new int[] { tri.i3, newPointIndex, tri.i2});
52.         Debug.LogFormat("[{0},{1},{2}]", tri.i1, tri.i2, tri.i3);
53.  
54.         mesh.Clear();
55.         mesh.vertices = vertexBuffer.ToArray();
56.         mesh.SetTriangles(  trianglesBuffer.ToArray(),0);
57.         mesh.RecalculateNormals();
58.  
59.     }
60.  
61.     Triangle GetTriangle( int[] triangles, Vector3[] vertexes,int triangleIndex)
62.     {
63.         Triangle triangle = new Triangle();
64.         int baseIndex = triangleIndex * 3;
65.         triangle.i1 = triangles[baseIndex];
66.         triangle.i2 = triangles[baseIndex + 1];
67.         triangle.i3 = triangles[baseIndex + 2];
68.         triangle.p1 = vertexes[triangle.i1];
69.         triangle.p2 = vertexes[triangle.i2];
70.         triangle.p3 = vertexes[triangle.i3];
71.         return triangle;
72.     }

 

sloved, I didn't update meshcollider's mesh