diff --git a/tools/gen_marching_cubes_conf.py b/tools/gen_marching_cubes_conf.py
index 899a462..8c76a14 100644
--- a/tools/gen_marching_cubes_conf.py
+++ b/tools/gen_marching_cubes_conf.py
@@ -83,6 +83,19 @@ class TriangulatedCube:
             n_act.add(transf(act))
         return TriangulatedCube(n_act, n_tri)
 
+    def reverse_activated(self):
+        all_elts = {
+            Vert.frnt_bot_l,
+            Vert.frnt_bot_r,
+            Vert.frnt_top_l,
+            Vert.frnt_top_r,
+            Vert.back_bot_l,
+            Vert.back_bot_r,
+            Vert.back_top_l,
+            Vert.back_top_r,
+        }
+        self.activated = all_elts - self.activated
+
     def activated_code(self):
         out = 0
         for act in self.activated:
@@ -181,11 +194,14 @@ def do_main(base_cases):
         index[code] = case
 
     for transf in transforms:
-        for case in base_cases:
-            tr_case = case.transform(transf)
-            code = tr_case.activated_code()
-            if index[code] is None:
-                index[code] = tr_case
+        for rev_activated in [False, True]:
+            for case in base_cases:
+                tr_case = case.transform(transf)
+                if rev_activated:
+                    tr_case.reverse_activated()
+                code = tr_case.activated_code()
+                if index[code] is None:
+                    index[code] = tr_case
 
     for (val, tri) in enumerate(index):
         if tri is None: