Question Store Player Position and reycast it for deleting triangle return wrong triangle index

Hi everyone,
i'm new with unity and i'm programming a lot for learn but now i encountered a problem.
I need to get the Triangle Index of specific mesh (in specific layer) for destroiyng it when a player walking on.
i Try this code and Attach to the mesh i want to "destroy" but when the condition is triggered the deleted Triangles are not correct.
What i do is start collect the position of character at colision enter and stop it at collision exit then i need to destroy all the triangles in the collected position.
First code is very simple:
I set a condition for update

Code (CSharp):

1. void OnCollisionEnter(Collision collision)
2.     {
3.         entered= true;
4.      
5.      
6.     }

After that in te Update function if entered is true i collect every Player Vector3 position:

Code (CSharp):

1.  
2. if (entered)
3.         {
4.             if(last_position!= player.transform.position)
5.             {
6.                 last_position= player.transform.position;
7.              
8.              
9.            
10.                 position.Add(last_position);
11.              
12.             }
13.          
14. }

Now in the exit collision event i do this:

Code (CSharp):

1.  entered= false;
2.        
3.         int layerMask = 1 << 8;
4.      
5.         layerMask = ~layerMask;
6.         int j = 0;
7.    
8.  
9.         RaycastHit hit;
10.         Ray ray;
11.         while (j < position.Count)
12.         {
13.          
14.          
15.             if (Physics.Raycast(position[j], Vector3.down, out hit, 100,layerMask))
16.             {
17.            
18.                 delete_triangle(hit.triangleIndex);
19.             }
20.         }
21.      
22.  
23.      
24.         position.Clear();

And this is the delete_triangle function where i receive an error "IndexOutOfRangeException: Index was outside the bounds of the array" at the below marked line and i notice that the Triangle Index is always -1

Code (CSharp):

1.      
2. Destroy(this.gameObject.GetComponent<MeshCollider>());
3.         mesh = GetComponent<MeshFilter>().mesh;
4.         int[] old_trangle = mesh.triangles;
5.         int[] new_triangle = new int[mesh.triangles.Length - 3];
6.  
7.         int i = 0;
8.         int j = 0;
9.         while (j < old_trangle.Length)
10.         {
11.             if (j != triangle_index * 3)
12.             {
13.                [COLOR=#ff0000] new_triangle [i++] = old_trangle[j++];[/COLOR]
14.                 new_triangle [i++] = old_trangle[j++];
15.                 new_triangle [i++] = old_trangle[j++];
16.             }
17.             else
18.             {
19.                 j += 3;
20.             }
21.  
22.          
23.         }
24.  
25.         this.gameObject.AddComponent<MeshCollider>();
26.         transform.GetComponent<MeshFilter>().mesh.triangles = new_triangle ;

Thank you in advance for your help

 

So,
i figure out how to do this but now i have another problem.
The new setup is that i save all the position i want to reycast for find triangle to delete but the deleted triangles are wrong.
The loop is:

Code (CSharp):

1. int layer_mask = LayerMask.GetMask("SafeZone");
2.         RaycastHit hit;
3.    
4.           int k = 0;
5.  
6.         int layer_mask = LayerMask.GetMask("SafeZone");
7.         while (k < position.Count)
8.         {
9.    
10.             if (Physics.Raycast(position[k], -Vector3.up, out hit, Mathf.Infinity, layer_mask))
11.             {
12.               Debug.DrawRay(position[k], -Vector3.up * hit.distance, Color.yellow,100);
13.                delete_triangle(hit.triangleIndex);
14.             }
15.             k++;
16.         }
17.         position.Clear();

The delete_triangle function is:

Code (CSharp):

1.  
2. void delete_triangle(int index)
3.     {
4.    
5.         Destroy(safezone.gameObject.GetComponent<MeshCollider>());
6.         Mesh mesh = safezone.transform.GetComponent<MeshFilter>().mesh;
7.         mesh.MarkDynamic();
8.    
9.         int[] old_triangle = mesh.triangles;
10.         int[] new_triangle = new int[mesh.triangles.Length-3];
11.    
12.         int i = 0;
13.         int j = 0;
14.    
15.         while (j < old_triangle.Length)
16.         {
17.             if (j != index*3)
18.             {
19.            
20.                 new_triangle[i++] = old_triangle[j++];
21.                 new_triangle[i++] = old_triangle[j++];
22.                 new_triangle[i++] = old_triangle[j++];
23.             }
24.             else
25.             {
26.                 j += 3;
27.             }
28.        
29.         }
30.         safezone.gameObject.layer = 8;
31.         safezone.transform.GetComponent<MeshFilter>().mesh.triangles = new_triangle ;
32.         safezone.gameObject.AddComponent<MeshCollider>();
33.     }
34.  

Now for testing purpose i draw a line where the postion trigger the hit and as you will notice the new mesh is wrong:

 

Nobody can help me?