// Draws a line from the bottom left
    // to the top right of the Screen
    // Using GL.Vertex3
    var mat : Material;
    function OnPostRender() {
        if (!mat) {
            Debug.LogError("Please Assign a material on the inspector");
            return;
        }
        GL.PushMatrix();
        mat.SetPass(0);
        GL.LoadOrtho();
        GL.Begin(GL.LINES);
        GL.Vertex3(0,0,0);
        GL.Vertex3(1,1,0);
        GL.End();
        GL.PopMatrix();
    }

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public Material mat;
    void OnPostRender() {
        if (!mat) {
            Debug.LogError("Please Assign a material on the inspector");
            return;
        }
        GL.PushMatrix();
        mat.SetPass(0);
        GL.LoadOrtho();
        GL.Begin(GL.LINES);
        GL.Vertex3(0, 0, 0);
        GL.Vertex3(1, 1, 0);
        GL.End();
        GL.PopMatrix();
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public mat as Material

    def OnPostRender():
        if not mat:
            Debug.LogError('Please Assign a material on the inspector')
            return
        GL.PushMatrix()
        mat.SetPass(0)
        GL.LoadOrtho()
        GL.Begin(GL.LINES)
        GL.Vertex3(0, 0, 0)
        GL.Vertex3(1, 1, 0)
        GL.End()
        GL.PopMatrix()