diff --git a/bin/iterate.py b/bin/iterate.py
index 2dd8465..a8d9c55 100644
--- a/bin/iterate.py
+++ b/bin/iterate.py
@@ -11,6 +11,7 @@ if __name__ == '__main__':
             '(first argument) and dump json to stdout')
     parser.add_argument('type', choices=('cc', 'butterfly'))
     parser.add_argument('mesh')
+    parser.add_argument('refines', type=int)
     opt = parser.parse_args()
 
     cube = json.load(open(opt.mesh, 'r'))
@@ -21,5 +22,6 @@ if __name__ == '__main__':
     else:
         refine = butterfly.refine
 
-    q = refine(p)
-    print(q)
+    for i in range(opt.refines):
+        p = refine(p)
+    print(p)
diff --git a/surf/geometry.py b/surf/geometry.py
index c2a3e67..5f814a6 100644
--- a/surf/geometry.py
+++ b/surf/geometry.py
@@ -152,6 +152,8 @@ class PolygonMesh(object):
         self._edges_for_vert = kwargs.get('edges for vert', None)
         self._faces_for_vert = kwargs.get('faces for vert', None)
 
+        self._edge_map = None
+
     @property
     def faces_for_edge(self):
         """returns a list of face indices for a given edge index.
@@ -168,17 +170,14 @@ class PolygonMesh(object):
         where 0 and 1 are indices into the face list
         """
         if self._faces_for_edge is None:
-            # TODO: eventually support generating this ourselves ...
-            raise NotImplementedError
+            self._set_up_face_edge_connectivity()
         return self._faces_for_edge
 
     @property
     def edges_for_face(self):
         """returns a list of edge indices for a given face index."""
-        # XXX
         if self._edges_for_face is None:
-            self._edges_for_face = [[] for i in range(len(self.faces))]
-
+            self._set_up_face_edge_connectivity()
         return self._edges_for_face
 
     @property
@@ -201,6 +200,27 @@ class PolygonMesh(object):
                     self._faces_for_vert[vid].append(i)
         return self._faces_for_vert
 
+    def _make_edge_map(self):
+        self._edge_map = {}
+        for i, edge in enumerate(self.edges):
+            self._edge_map[tuple(sorted(edge))] = i
+
+    def _set_up_face_edge_connectivity(self):
+        if self._edge_map is None: 
+            self._make_edge_map()
+        self._edges_for_face = [[] for i in range(len(self.faces))]
+        self._faces_for_edge = [[] for i in range(len(self.edges))]
+        for face_id, face in enumerate(self.faces):
+            for i in range(len(face) -1):
+                cur_edge = tuple(sorted([face[i], face[i+1]]))
+                edge_id = self._edge_map[cur_edge]
+                self._edges_for_face[face_id].append(edge_id)
+                self._faces_for_edge[edge_id].append(face_id)
+            cur_edge = tuple(sorted([face[-1], face[0]]))
+            edge_id = self._edge_map[cur_edge]
+            self._edges_for_face[face_id].append(edge_id)
+            self._faces_for_edge[edge_id].append(face_id)
+
     def __unicode__(self):
         # TODO: perhaps also add connectivity here?
         d = {
diff --git a/surf/test/test_polymesh.py b/surf/test/test_polymesh.py
index 6e3d277..0ce8310 100644
--- a/surf/test/test_polymesh.py
+++ b/surf/test/test_polymesh.py
@@ -43,6 +43,14 @@ class TestPM(unittest.TestCase):
         for pi, qi in zip(self.skel.edges_for_vert, self.cube.edges_for_vert):
             self.assertEqual(sorted(pi), sorted(qi))
 
+    def test_edges_for_face(self):
+        for pi, qi in zip(self.skel.edges_for_face, self.cube.edges_for_face):
+            self.assertEqual(sorted(pi), sorted(qi))
+
+    def test_faces_for_edge(self):
+        for pi, qi in zip(self.skel.faces_for_edge, self.cube.faces_for_edge):
+            self.assertEqual(sorted(pi), sorted(qi))
+
 
 if __name__ == '__main__':
     unittest.main(verbosity=3)