Explain how to modify model scale in readme

README.md

@@ -5,9 +5,10 @@ Augmented reality card based application with Python, numpy and OpenCV
 
 * Place the image of the surface to be tracked inside the `reference` folder.
 * On line 36 of `src/ar_main.py` replace `'model.jpg'` with the name of the image you just copied inside the `reference` folder.
-* On line 40 of `src/ar_main.py` replace `'fox.obj'` with the name of the model you want to render.
+* On line 40 of `src/ar_main.py` replace `'fox.obj'` with the name of the model you want to render. To change the size of the rendered model change the scale parameter (number `3`) in line 103 of `src/ar_main.py` by a suitable number. This might require some trial and error.
 * Open a terminal session inside the project folder and run `python src/ar_main.py`
 
+
 ### Command line arguments
 
 * `--rectangle`, `-r`: Draws the projection of the reference surface on the video frame as a blue rectangle.