2d custom mesh triangulator problem

Hello i having some trouble with well known triangulator class.I implemented the triangulator class directly without an edit.My aim is to create a volumetric light depending on the direction but im having this issue relative with triangles appearently.

Another view i keep the positions of the red colored rays start&end locations and i put these locations as vertices in MESH FILTER component.

 public void buildSingleVolume()
     {
         
 
         Mesh _mesh = new Mesh ();
         _mesh.name = "VolumeMesh";
 
         for (int i = 0; i < _vert2d.Length; i++)
         {
             _vert3d [i] = new Vector3 (_vert2d[i].x,_vert2d[i].y,0);
         }
 
         Triangulator _tr = new Triangulator (_vert2d);
         int[] indices = _tr.Triangulate ();
     
 
         _mesh.vertices = _vert3d;
         _mesh.triangles =indices;
         _mesh.RecalculateNormals ();
         _mesh.RecalculateBounds ();
 
 
         GameObject _instance = Instantiate (volume, Vector2.zero,new Quaternion(0,0,0,0)) as GameObject;
         _instance.tag = "VolumeL";
         _instance.GetComponent<MeshFilter> ().mesh = _mesh;
     }

the mesh would show up with exact positions of red rays but it has many zig-zag or false structure.