Reuse noise table.

undergen.lua

@@ -9,6 +9,7 @@ local max_depth = 31000
 
 local terrain_noise = {offset = 15, scale = 10, seed = 3721, spread = {x = 40, y = 40, z = 40}, octaves = 3, persist = 1, lacunarity = 2}
 local terrain_map
+local terrain = {}
 
 
 underworlds_mod.undergen = function(minp, maxp, data, p2data, area, node, underzone)
@@ -28,7 +29,7 @@ underworlds_mod.undergen = function(minp, maxp, data, p2data, area, node, underz
     end
   end
 
-	local terrain = terrain_map:get2dMap_flat({x=minp.x, y=minp.z})
+	terrain = terrain_map:get2dMap_flat({x=minp.x, y=minp.z}, terrain)
 	if not terrain then
 		return
 	end