###1.set up a default renderer


		defaultRenderer = gameObject.GetComponent();
		defaultRenderer.material = new Material (shader);
		defaultRenderer.SetVertexCount (0);
		defaultRenderer.SetWidth (0.1f, 0.1f);
		defaultRenderer.SetColors (Color.green, Color.green);
		defaultRenderer.useWorldSpace = true;

###2.create a panel to draw on


		panel = GameObject.Find ("DrawingPanel");

###3.the main code in Update()


		if (Input.GetMouseButtonDown (0)) {
			//to check if this line renderer is used. If it is, create a new line renderer(on a new Gameobject)
			//(so that more than 1 lines can be rendered)
			if(!used){
				used = true;
				isMousePressed = true;
				defaultRenderer.SetVertexCount (0);
				pointList.RemoveRange (0, pointList.Count);
			}else if(!newCreated){
				//to draw more than 1 lines, we have to create a new gameObejct
				GameObject newRenderer = GameObject.Instantiate (rendererPrefab);
				newCreated = true;
				newRenderer.GetComponent ().init(id+1);
			}
		}
		if (Input.GetMouseButtonUp (0)) {
			isMousePressed = false;}
		if (isMousePressed) {
			mousePos = Camera.main.ScreenToWorldPoint (Input.mousePosition);
			mousePos.z = 0;
			if (Input.mousePosition.x < panel.GetComponent().offsetMin.x || 
				Input.mousePosition.x > (Screen.width + panel.GetComponent().offsetMax.x)){ 
				return;
			}
			//To draw just in the area of panel
			if (Screen.height - Input.mousePosition.y < (-panel.GetComponent().offsetMax.y) || 
				Screen.height - Input.mousePosition.y > (Screen.height - panel.GetComponent().offsetMin.y)){ 
				return;
			}
			if (!pointList.Contains (mousePos)) {
				pointList.Add (mousePos);
				defaultRenderer.SetVertexCount (pointList.Count);
				defaultRenderer.SetPosition (pointList.Count - 1, (Vector3)pointList [pointList.Count - 1]);
			}
		}