Renders normals of a geometry mesh in Unity

NormalRenderer.cs

using UnityEngine;
using System.Collections;

public class NormalRenderer : MonoBehaviour 
{
	public float Threshold = 360.0f;
	public float Offset = 0;

	void OnDrawGizmos()
	{
		Vector3[] normals = GetComponent<MeshFilter>().sharedMesh.normals;
		Vector3[] vertices = GetComponent<MeshFilter>().sharedMesh.vertices;
		int[] triangles = GetComponent<MeshFilter>().sharedMesh.triangles; //contains vertex indices for vertices building a triangle
		
		for(int i = 0;i<triangles.Length; i+=3)
		{
			//only use normals of first vertex ->flatten shading (else we have to use an average value of all 3 normals of the triangle)
			int v1 = triangles[i]; 
			int v2 = triangles[i+1];
			int v3 = triangles[i+2];
			
//			Vector3 p = vertices[v1];
			
//			p = this.transform.TransformPoint(p);
			Vector3 n = this.transform.TransformDirection(normals[v1]);
			
			Vector3 middle = (vertices[v1] + vertices[v2] + vertices[v3]) / 3;
			middle = this.transform.TransformPoint(middle);

			if(Vector3.Angle(Vector3.down, n) <= Threshold)
			{
				Gizmos.DrawLine(middle + n.normalized * Offset, middle + n);
			}

//			Gizmos.DrawLine(p, p + n);

		}
	}
}