diff --git a/chunk.py b/chunk.py
index 1fe427b..35c14c8 100644
--- a/chunk.py
+++ b/chunk.py
@@ -273,11 +273,14 @@ class ChunkRenderer(object):
                         # TODO torches, redstone torches, crops, ladders, stairs, 
                         #      levers, doors, buttons, and signs all need to be handled here (and in textures.py)
 
-                        ## minecart track, crops, ladder, doors
-                        if blockid in (66,59,61,62, 65,64,71):
+                        ## minecart track, crops, ladder, doors, etc.
+                        if blockid in textures.special_blocks:
                          # also handle furnaces here, since one side has a different texture than the other
                             ancilData = blockData_expanded[x,y,z]
-                            t =  textures.generate_special_texture(blockid, ancilData)
+                            try:
+                                t = textures.specialblockmap[(blockid, ancilData)]
+                            except KeyError:
+                                t = None
 
                         else:
                             t = textures.blockmap[blockid]
diff --git a/textures.py b/textures.py
index 1ba595c..65dd855 100644
--- a/textures.py
+++ b/textures.py
@@ -485,3 +485,25 @@ def generate_special_texture(blockID, data):
     
 
     return None
+
+
+# This set holds block ids that require special pre-computing.  These are typically
+# things that require ancillary data to render properly (i.e. ladder plus orientation)
+special_blocks = set([66,59,61,62, 65,64,71])
+
+# this is a map of special blockIDs to a list of all 
+# possible values for ancillary data that it might have.
+special_map = {}
+special_map[66] = range(10) # minecrart tracks
+special_map[59] = range(8)  # crops
+special_map[61] = (0,)      # furnace
+special_map[62] = (0,)      # burning furnace
+special_map[65] = (2,3,4,5) # ladder
+special_map[64] = range(16) # wooden door
+special_map[71] = range(16) # iron door
+
+specialblockmap = {}
+
+for blockID in special_blocks:
+    for data in special_map[blockID]:
+        specialblockmap[(blockID, data)] = generate_special_texture(blockID, data)