diff --git a/DiffractionGratings/README.txt b/DiffractionGratings/README.txt
index d6d55d13d1dacf66ad19f66ef022283caa8be51d..68eddaafc367d241b7bac6daf3fc7bdad78ba0a2 100644
--- a/DiffractionGratings/README.txt
+++ b/DiffractionGratings/README.txt
@@ -1,10 +1,16 @@
 Parametric model of diffraction gratings
 
-Quick start
------------
+Quick start 2D
+--------------
 
 Open `grating2D.pro' with Gmsh.
 
+Quick start 3D
+--------------
+
+To run the test cases, type in the command line :
+'gmsh grating3D.pro -setstring test_case hole'
+
 Additional info
 ---------------