added some logging to hunt down why q wasn't being populated

interp/grid/__init__.py

@@ -27,9 +27,13 @@ class grid(object):
 
     if verts != None:
       self.verts = np.array(verts)
-      self.tree           = KDTree(self.verts)
-    if q:
+      self.tree  = KDTree(self.verts)
+
+    if q != None:
+      log.debug("found q")
       self.q = np.array(q)
+    else:
+      log.debug("no q")
 
     self.cells          = {}
     self.cells_for_vert = defaultdict(list)