diff --git a/API.md b/API.md
index c0e1757..ba028db 100644
--- a/API.md
+++ b/API.md
@@ -41,7 +41,7 @@ The shapes are defined as follows:
 
     func = function(pos, n)
         return 2 * n
-    end
+    end,
     -- Function to edit the NoiseParams based on some operation.
     -- Keep in mind that this function will be run many, many times, so it is
     -- best to keep this function as trivial as possible.
diff --git a/lua/engine.lua b/lua/engine.lua
index 59cea27..a38eded 100644
--- a/lua/engine.lua
+++ b/lua/engine.lua
@@ -8,8 +8,8 @@ end
 local function from_flat_to_3d(i, nx, ny)
     return {
         dx = (i - 1) % nx,
-        dy = (i - 1) // nx % ny,
-        dz = (i - 1) // nx // ny
+        dy = math.floor((i - 1) / nx) % ny,
+        dz = math.floor((i - 1) / (nx * ny))
     }
 end
 
@@ -22,9 +22,9 @@ local function iter_3d_area(minp, maxp, callback)
     for i = 1, nx * ny * nz do
         local dpos = from_flat_to_3d(i, nx, ny)
         local pos = {
-            x = minp.x + dpos.x,
-            y = minp.y + dpos.y,
-            z = minp.z + dpos.z,
+            x = minp.x + dpos.dx,
+            y = minp.y + dpos.dy,
+            z = minp.z + dpos.dz,
         }
 
         callback(i, pos)
@@ -185,8 +185,8 @@ local function get_threshold_flat(minp, maxp)
         for _, n in pairs(noise) do
             local v = n.noise[i]
 
-            local dx = math.abs(x - n.def.connectivity)
-            local dy = math.abs(y - n.def.verticality)
+            local dx = math.abs(x - n.def.connectivity_point)
+            local dy = math.abs(y - n.def.verticality_point)
 
             local w = math.abs(shape_distance_weight(
                 #noordstar_caves.registered_shapes, dx, dy
@@ -231,7 +231,7 @@ noordstar_caves.set_world_depth(world_depth)
 --  - Make sure that the output changes VERY SLOWLY over time
 --  - This function will be run a LOT so it is very performance sensitive
 noordstar_caves.cave_vastness = function(pos)
-    return math.abs(pos.y) / world_depth
+    return pos.y / world_depth
 end
 
 -- Secretly, we're using an internal function that also adds a safe layer for
@@ -240,28 +240,54 @@ local function cave_vastness(pos)
     if world_depth + 20 < pos.y then
         return noordstar_caves.cave_vastness(pos)
     elseif world_depth + 5 < pos.y then
-        return noordstar_caves.cave_vastness(pos) * math.abs(y - world_depth - 5) / 15
+        return noordstar_caves.cave_vastness(pos) * math.abs(pos.y - world_depth - 5) / 15
     else
-        return -1000
+        return 0
     end
 end
 
+local tpd_yet = false
+
 minetest.register_on_generated(function(minp, maxp, blockseed)
+    if maxp.y < world_depth then
+        return
+    end
+
     -- Get voxelmanip
     local vm = minetest.get_mapgen_object("voxelmanip")
     local data = vm:get_data()
     
     -- Get threshold values
     local thresholds = get_threshold_flat(minp, maxp)
-    local air = minetest.get_content_id("air")
+    local air = minetest.get_content_id("mcl_core:glass")
+
+    local count = 0
 
     iter_3d_area(minp, maxp, function(i, pos)
-        if thresholds[i] >= cave_vastness(pos) then
-            data[i] = air
+        local nx = maxp.x - minp.x + 1 + 32
+        local ny = maxp.y - minp.y + 1 + 32
+
+        local dx = pos.x - minp.x
+        local dy = pos.y - minp.y
+        local dz = pos.z - minp.z
+
+
+        local vi = from_3d_to_flat(dx + 16, dy + 16, dz + 16, nx, ny)
+
+        if not data[vi] then
+            error("Vi is not in data (len " .. #data .. "): " .. vi .. " for (dx, dy, dz) = (" .. dx .. ", " .. dy .. ", " .. dz .. ") with minp = (" .. minp.x .. ", " .. minp.y .. ", " .. minp.z .. ") and maxp = (" .. maxp.x .. ", " .. maxp.y .. ", " .. maxp.z .. ") and pos = (" .. pos.x .. ", " .. pos.y .. ", " .. pos.z .. ")")
+        end
+        
+        if thresholds[i] >= (1 - cave_vastness(pos)) then
+            data[vi] = air
+
+            count = count + 1
         end
     end)
 
     -- Write all changes to the Minetest world
     vm:set_data(data)
     vm:write_to_map()
+
+    minetest.chat_send_all("Updated " .. count .. " squares")
 end)