Kelp store age metadata by bulk on a queue, improve API, etc.

Highlights:
- Implement storing age metadata by bulk on a queue, with maximum interval and queue length.
- "Flexible" initial growth probability. Will provide helper APIs.
- Fix various bugs with unsubmerged kelp detection, submerged tip detection, age metadata.
- Various optimizations.

mods/ITEMS/mcl_ocean/kelp.lua

@@ -1,8 +1,9 @@
 -- TODO: whenever it becomes possible to fully implement kelp without the
--- plantlike_rooted limitation, please adapt the code accordingly.
+-- plantlike_rooted limitation, please update accordingly.
 --
 -- TODO: In MC, you can't actually destroy kelp by bucket'ing water in the middle.
 -- However, because of the plantlike_rooted hack, we'll just allow it for now.
+-- TODO: Integrate ABMs with the new kelp code, disabled. OR remove them entirely
 
 local S = minetest.get_translator("mcl_ocean")
 local mod_doc = minetest.get_modpath("doc") ~= nil
@@ -15,6 +16,7 @@ local mt_registered_items = minetest.registered_items
 local mt_registered_nodes = minetest.registered_nodes
 
 -- functions
+local mt_log = minetest.log
 local mt_add_item = minetest.add_item
 local mt_get_item_group = minetest.get_item_group
 local mt_get_node = minetest.get_node
@@ -22,21 +24,31 @@ local mt_get_node_level = minetest.get_node_level
 local mt_get_node_max_level = minetest.get_node_max_level
 local mt_get_node_or_nil = minetest.get_node_or_nil
 local mt_get_node_timer = minetest.get_node_timer
-local mt_hash_node_position = minetest.hash_node_position
-local mt_is_protected = minetest.is_protected
-local mt_set_node = minetest.set_node
 local mt_get_meta = minetest.get_meta
+local mt_hash_node_position = minetest.hash_node_position
+local mt_pos_to_string = minetest.pos_to_string
+local mt_is_protected = minetest.is_protected
+local mt_record_protection_violation = minetest.record_protection_violation
+local mt_set_node = minetest.set_node
 
 local mt_is_creative_enabled = minetest.is_creative_enabled
 local mt_sound_play = minetest.sound_play
 
+local math_min = math.min
+local math_max = math.max
+local math_ceil = math.ceil
 local math_floor = math.floor
 local math_random = math.random
 local string_format = string.format
+local table_copy = table.copy
+local table_insert = table.insert
 
 -- DEBUG: functions
 local log = minetest.log
 local chatlog = minetest.chat_send_all
+il_chatlog = chatlog
+il_get_meta = mt_get_meta
+il_hash_pos = mt_hash_node_position
 
 --------------------------------------------------------------------------------
 -- Kelp API
@@ -45,30 +57,51 @@ local chatlog = minetest.chat_send_all
 local kelp = {}
 mcl_ocean.kelp = kelp
 
+-- Kelp minimum and maximum age. Once reached the maximum, kelp no longer grows.
+kelp.MIN_AGE = 0
 kelp.MAX_AGE = 25
-kelp.TIMER_INTERVAL = 0.2
+
+-- Tick interval (in seconds) for updating kelp.
+kelp.TICK = 0.2
+
+-- Tick interval (in seconds) to store kelp meta.
+kelp.META_TICK = 2
+
+-- Max age queue length
+kelp.MAX_AGE_QUEUE = 20
 
 -- The average amount of growth for kelp in a day is 2.16 (https://youtu.be/5Bp4lAjAk3I)
--- Normally, a day lasts 20 minutes, meaning this nodetimer is executed 24000 times.
+-- Normally, a day lasts 20 minutes, meaning kelp.next_grow() is executed
--- Calculate probability via 2.16/24000 and we get the probability 9/100'000 or 9.0e-5
+-- 1200 / TICK times. Per tick probability = (216/100) / (1200/TICK)
--- NOTE: currently, we can't exactly use the same type of randomness MC does,
+-- NOTE: currently, we can't exactly use the same type of randomness MC does, because
--- because it has multiple complicated sets of PRNGs.
+-- it has multiple complicated sets of PRNGs.
--- kelp.RANDOM_NUMERATOR = 9
+-- NOTE: Small loss of precision, should be 10 to preserve it.
-kelp.RANDOM_NUMERATOR = 100
+-- kelp.ROLL_GROWTH_PRECISION = 10
-kelp.RANDOM_DENOMINATOR = 100000
+-- kelp.ROLL_GROWTH_NUMERATOR = 216 * kelp.TICK * kelp.ROLL_GROWTH_PRECISION
+-- kelp.ROLL_GROWTH_DENOMINATOR = 100 * 1200 * kelp.ROLL_GROWTH_PRECISION
+kelp.ROLL_GROWTH_PRECISION = 1
+kelp.ROLL_GROWTH_NUMERATOR = 216 * kelp.TICK
+kelp.ROLL_GROWTH_DENOMINATOR = 100 * 1200
 
+-- Sounds used to dig and place kelp.
 kelp.leaf_sounds = mcl_sounds.node_sound_leaves_defaults()
 
 -- TODO: is this really necessary
 -- Lock drops to avoid duplicate drops, set after dropping detached kelp.
 kelp.lock_drop = 0
 
--- Registrar of nodetimers, indexed by pos_hash.
+-- Pool storing nodetimers
-kelp.registered_nodetimers = {}
+kelp.timers_pool = {}
 
 -- Pool storing age, indexed by pos_hash.
 kelp.age_pool = {}
 
+-- Queue(List) of hashed positions to save their ages.
+-- Invalid ones may still persist in this queue.
+kelp.age_queue = {}
+-- Stores only valid positions of each hashed postiions.
+kelp.age_queue_pos = {}
+
 
 -- is age in the growable range?
 function kelp.is_age_growable(age)
@@ -78,9 +111,10 @@ end
 
 -- Is this water?
 -- Returns the liquidtype, if indeed water.
-function kelp.is_submerged(node, def)
+function kelp.is_submerged(node)
 	if mt_get_item_group(node.name, "water") ~= 0 then
-		return def.liquidtype -- Expected only "source" and "flowing" from water liquids
+		-- Expected only "source" and "flowing" from water liquids
+		return mt_registered_nodes[node.name].liquidtype
 	end
 	return false
 end
@@ -88,16 +122,19 @@ end
 
 -- Is the water downward flowing?
 -- (kelp can grow/be placed inside downward flowing water)
-function kelp.is_downward_flowing(pos, node, def, is_above)
+function kelp.is_downward_flowing(pos, node, pos_above, node_above, __is_above__)
+	-- Function params: (pos[, node]) or (node, pos_above) or (node, node_above)
+	local node = node or mt_get_node(pos)
+
 	local result = (math_floor(node.param2 / 8) % 2) == 1
-	if not (result or is_above) then
+	if not (result or __is_above__) then
 		-- If not, also check node above.
 		-- (this is needed due a weird quirk in the definition of "downwards flowing"
 		-- liquids in Minetest)
-		local node_above = mt_get_node({x=pos.x,y=pos.y+1,z=pos.z})
+		local pos_above = pos_above or {x=pos.x,y=pos.y+1,z=pos.z}
-		local def_above = mt_registered_nodes[node_above.name]
+		local node_above = node_above or mt_get_node(pos_above)
-		result = kelp.is_submerged(node_above, def_above)
+		result = kelp.is_submerged(node_above)
-			or kelp.is_downward_flowing(pos, node_above, def_above, true)
+			or kelp.is_downward_flowing(nil, node_above, nil, nil, true)
 	end
 	return result
 end
@@ -105,20 +142,23 @@ end
 
 -- Will node fall at that position?
 -- This only checks if a node would fall, meaning that node need not be at pos.
-function kelp.is_falling(pos, node)
+function kelp.is_falling(pos, node, is_falling, pos_bottom, node_bottom, def_bottom)
+	-- Optional params: is_falling, pos_bottom, node_bottom, def_bottom
+
 	-- NOTE: Modified from check_single_for_falling in builtin.
-	-- Please update as necessary.
+	-- Please update accordingly.
 	local nodename = node.name
 
-	if mt_get_item_group(nodename, "falling_node") == 0 then
+	if is_falling == false or
+		is_falling == nil and mt_get_item_group(nodename, "falling_node") == 0 then
 		return false
 	end
 
-	local pos_bottom = {x = pos.x, y = pos.y - 1, z = pos.z}
+	local pos_bottom = pos_bottom or {x = pos.x, y = pos.y - 1, z = pos.z}
 	-- get_node_or_nil: Only fall if node below is loaded
-	local node_bottom = mt_get_node_or_nil(pos_bottom)
+	local node_bottom = node_bottom or mt_get_node_or_nil(pos_bottom)
 	local nodename_bottom = node_bottom.name
-	local def_bottom = node_bottom and mt_registered_nodes[nodename_bottom]
+	local def_bottom = def_bottom or node_bottom and mt_registered_nodes[nodename_bottom]
 	if not def_bottom then
 		return false
 	end
@@ -143,6 +183,20 @@ function kelp.is_falling(pos, node)
 end
 
 
+-- Roll whether to grow kelp or not.
+function kelp.roll_growth(numerator, denominator)
+	-- Optional params: numerator, denominator
+	return math_random(denominator or kelp.ROLL_GROWTH_DENOMINATOR) <= (numerator or kelp.ROLL_GROWTH_NUMERATOR)
+end
+
+
+-- Roll initial age for kelp.
+function kelp.roll_init_age(min, max)
+	-- Optional params
+	return math_random(min or kelp.MIN_AGE, (max or kelp.MAX_AGE)-1)
+end
+
+
 -- Converts param2 to kelp height.
 function kelp.get_height(param2)
 	return math_floor(param2 / 16)
@@ -150,28 +204,31 @@ end
 
 
 -- Obtain pos and node of the tip of kelp.
-function kelp.get_tip(pos, node)
+function kelp.get_tip(pos, param2)
-	local size = math.ceil(node.param2 / 16)
+	-- Optional params: param2
-	local pos_tip = table.copy(pos)
+	local height = kelp.get_height(param2 or mt_get_node(pos).param2)
-	pos_tip.y = pos_tip.y + size
+	local pos_tip = {x=pos.x, y=pos.y, z=pos.z}
-	return pos_tip, mt_get_node(pos_tip)
+	pos_tip.y = pos_tip.y + height + 1
+	return pos_tip, mt_get_node(pos_tip), height
 end
 
 
 -- Obtain position of the first kelp unsubmerged.
-function kelp.find_unsubmerged(pos, node)
+function kelp.find_unsubmerged(pos, node, height)
+	-- Optional params: node, height
+	local node = node or mt_get_node(pos)
+	local height = height or kelp.get_height(node.param2)
 
-	local x,y,z = pos.x, pos.y, pos.z
+	local walk_pos = {x=pos.x, z=pos.z}
-	local height = kelp.get_height(node.param2)
+	local y = pos.y
-	local walk_pos = {x=x, z=z}
 	for i=1,height do
 		walk_pos.y = y + i
 		local walk_node = mt_get_node(walk_pos)
-		if mt_get_item_group(walk_node.name, "water") == 0 then
+		if not kelp.is_submerged(walk_node) then
-			return walk_pos, walk_node
+			return walk_pos, walk_node, height, i
 		end
 	end
-	return nil
+	return nil, nil, height, height
 end
 
 
@@ -181,53 +238,145 @@ function kelp.next_param2(param2)
 end
 
 
--- Grow next kelp.
+-- Stores age from kelp.age_queue* into their respective meta
-function kelp.next_grow(pos, node, pos_tip, def_tip, downward_flowing)
+function kelp.store_meta()
-	-- Optional parameters
+	local count = 0
-	local pos_tip, def_tip = pos_tip, def_tip
+	for _ in pairs(kelp.age_queue_pos) do
-	local downward_flowing = downward_flowing
+		count = count + 1
-	if pos_tip == nil and def_tip == nil then
+	end
-		local node_tip
+	-- chatlog(string_format("Storing age metadata: %d in queue", #kelp.age_queue))
-		pos_tip, node_tip = kelp.get_tip(pos, node)
+	-- chatlog(string_format("Storing age metadata: %d valid in queue", count))
-		def_tip = mt_registered_nodes[node_tip.name]
+	for i=1,#kelp.age_queue do
-		downward_flowing = kelp.is_submerged(pos_tip, node_tip)
+		local pos_hash = kelp.age_queue[i]
-			and kelp.is_downward_flowing(pos_tip, node_tip, def_tip)
+		local pos = kelp.age_queue_pos[pos_hash]
+		-- queued hashes may no longer point to a valid pos, e.g. kelp is destroyed.
+		if pos then
+			mt_get_meta(pos):set_int("mcl_ocean:kelp_age", kelp.age_pool[pos_hash])
+		end
+	end
+	kelp.age_queue = {}
+	kelp.age_queue_pos = {}
+end
+
+
+-- Store and queue a kelp's age to be saved into meta later.
+function kelp.store_age(age, pos, pos_hash)
+	-- Watched params: pos
+	-- Optional params: pos_hash
+	local pos_hash = pos_hash or mt_hash_node_position(pos)
+
+	kelp.age_pool[pos_hash] = age
+	if not kelp.age_queue_pos[pos_hash] then
+		table_insert(kelp.age_queue, pos_hash)
+		kelp.age_queue_pos[pos_hash] = pos
+		return true, pos_hash
 	end
 
+	return false, pos_hash
+end
+
+
+-- Initialise a kelp's age.
+function kelp.init_age(pos, age, pos_hash, meta)
+	-- Watched params: pos
+	-- Optional params: age, pos_hash, meta
+	local pos_hash = pos_hash or mt_hash_node_position(pos)
+	local meta = meta or mt_get_meta(pos)
+
+	local age = age
+	if not meta:contains("mcl_ocean:kelp_age") then
+		-- NOTE: age param can only replace initial age roll.
+		age = age or kelp.roll_init_age()
+		kelp.store_age(age, pos, pos_hash)
+	else
+		age = meta:get_int("mcl_ocean:kelp_age")
+		if not kelp.age_pool[pos_hash] then
+			kelp.age_pool[pos_hash] = age
+		end
+	end
+
+	return age, pos_hash, meta
+end
+
+
+-- Initialise kelp nodetimer.
+function kelp.init_timer(pos, pos_hash)
+	-- Optional params: pos_hash
+	local pos_hash = pos_hash or mt_hash_node_position(pos)
+
+	local timer = kelp.timers_pool[pos_hash]
+	if not timer then
+		timer = mt_get_node_timer(pos)
+		kelp.timers_pool[pos_hash] = timer
+	end
+	if not timer:is_started() then
+		timer:start(kelp.TICK)
+	end
+
+	return pos_hash
+end
+
+
+-- Apply next kelp height.
+function kelp.next_height(pos, node, pos_tip, node_tip, submerged, downward_flowing)
+	-- Modified params: node
+	-- Optional params: node, pos_tip, node_tip, submerged, downward_flowing
+	local node = node or mt_get_node(pos)
+	local pos_tip = pos_tip
+	local node_tip = node_tip or (pos_tip and mt_get_node(pos_tip))
+	if not pos_tip then
+		pos_tip,node_tip = kelp.get_tip(pos)
+	end
+	local downward_flowing = downward_flowing or
+		(submerged or kelp.is_submerged(node_tip)
+		 and kelp.is_downward_flowing(pos_tip, node_tip))
+
 	-- Liquid source: Grow normally.
-	local node = table.copy(node)
 	node.param2 = kelp.next_param2(node.param2)
 	mt_set_node(pos, node)
 
 	-- Flowing liquid: Grow 1 step, but also turn the tip node into a liquid source.
 	if downward_flowing then
-		local alt_liq = def_tip.liquid_alternative_source
+		local alt_liq = mt_registered_nodes[node_tip.name].liquid_alternative_source
 		if alt_liq then
 			mt_set_node(pos_tip, {name=alt_liq})
 		end
 	end
+
+	return node, pos_tip, node_tip, submerged, downward_flowing
 end
 
 
--- Naturally grow next kelp.
+-- Grow next kelp.
-function kelp.natural_grow(pos, node, age, pos_hash, meta)
+function kelp.next_grow(age, pos, node, pos_hash, pos_tip, node_tip, submerged, downward_flowing)
-	-- Must grow first, then get the new meta
+	-- Watched params: pos
-	kelp.next_grow(pos, node)
+	-- Modified params: node
-
+	-- Optional params: node, pos_hash, pos_tip, node_tip, submerged, downward_flowing
-	-- Optional params
+	local node = node or mt_get_node(pos)
-	local meta = meta or mt_get_meta(pos)
 	local pos_hash = pos_hash or mt_hash_node_position(pos)
+	local pos_tip = pos_tip
+	local node_tip = node_tip or (pos_tip and mt_get_node(pos_tip))
+	if not pos_tip then
+		pos_tip,node_tip = kelp.get_tip(pos)
+	end
 
-	local age = age + 1
+	-- New kelp must also be submerged in water.
-	kelp.age_pool[pos_hash] = age
+	local downward_flowing = downward_flowing or kelp.is_downward_flowing(pos_tip, node_tip)
-	meta:set_int("mcl_ocean:kelp_age", age)
+	if not (submerged or kelp.is_submerged(node_tip)) then
+		return
+	end
 
+	kelp.next_height(pos, node, pos_tip, node_tip, submerged, downward_flowing)
+
+	return kelp.store_age(age, pos, pos_hash), node, pos_hash, pos_tip, node_tip, submerged, downward_flowing
 end
 
 
 -- Drops the items for detached kelps.
-function kelp.detach_drop(pos, height, pos_hash)
+function kelp.detach_drop(pos, param2, pos_hash)
-	local pos_hash = pos_hash or mt_hash_node_position(pos) -- Optional params
+	-- Optional params: param2, pos_hash
+	local height = kelp.get_height(param2 or mt_get_node(pos).param2)
+	local pos_hash = pos_hash or mt_hash_node_position(pos)
 
 	if kelp.lock_drop > 0 then
 		minetest.log("error",
@@ -236,9 +385,11 @@ function kelp.detach_drop(pos, height, pos_hash)
 		return
 	end
 
-	local x,y,z = pos.x,pos.y,pos.z
+	local y = pos.y
+	local walk_pos = {x=pos.x, z=pos.z}
 	for i=1,height do
-		mt_add_item({x=x, y=y+i, z=z}, "mcl_ocean:kelp")
+		walk_pos.y = y+i
+		mt_add_item(walk_pos, "mcl_ocean:kelp")
 	end
 
 	-- Locks drop.
@@ -251,7 +402,8 @@ end
 -- Synonymous to digging the kelp.
 -- NOTE: this is intended for whenever kelp truly becomes segmented plants
 -- instead of rooted to the floor. Don't try to remove dig_pos.
-function kelp.detach_dig(dig_pos, pos, node, is_drop, pos_hash)
+function kelp.detach_dig(dig_pos, pos, node, drop, pos_hash)
+	-- Optional params: drop, pos_hash
 	local pos_hash = pos_hash or mt_hash_node_position(pos)
 
 	local param2 = node.param2
@@ -260,17 +412,18 @@ function kelp.detach_dig(dig_pos, pos, node, is_drop, pos_hash)
 
 	-- Digs the entire kelp: invoke after_dig_node to mt_set_node.
 	if new_height <= 0 then
-		if is_drop then
+		if drop then
-			kelp.detach_drop(dig_pos, kelp.get_height(param2), pos_hash)
+			kelp.detach_drop(dig_pos, param2, pos_hash)
 		end
 		mt_set_node(pos, {
 			name=mt_registered_nodes[node.name].node_dig_prediction,
-			param=node.param, param2=0 })
+			param=node.param,
+			param2=0 })
 
 	-- Digs the kelp beginning at a height
 	else
-		if is_drop then
+		if drop then
-			kelp.detach_drop(dig_pos, kelp.get_height(param2) - new_height, pos_hash)
+			kelp.detach_drop(dig_pos, param2 - new_height, pos_hash)
 		end
 		mt_set_node(pos, {name=node.name, param=node.param, param2=16*new_height})
 	end
@@ -281,7 +434,6 @@ end
 -- Kelp callback functions
 --------------------------------------------------------------------------------
 
--- Set this to drop kelps when
 function kelp.surface_on_dig(pos, node, digger)
 	kelp.detach_dig(pos, pos, node, true)
 end
@@ -292,34 +444,47 @@ function kelp.surface_after_dig_node(pos, node)
 end
 
 
-function kelp.surface_on_timer(pos, elapsed)
+function kelp.surface_on_timer(pos)
 	local node = mt_get_node(pos)
-	local dig_pos = kelp.find_unsubmerged(pos, node)
 	local pos_hash = mt_hash_node_position(pos)
+
+	-- Update detahed kelps
+	local dig_pos = kelp.find_unsubmerged(pos, node)
 	if dig_pos then
+		-- chatlog("detach_dig")
 		kelp.detach_dig(dig_pos, pos, node, true, pos_hash)
 	end
 
 	-- Grow kelp on chance
-	if math_random(kelp.RANDOM_DENOMINATOR) - kelp.RANDOM_NUMERATOR < 0 then
+	if kelp.roll_growth() then
 		local age = kelp.age_pool[pos_hash]
 		if kelp.is_age_growable(age) then
-			kelp.natural_grow(pos, node, age, pos_hash)
+			kelp.next_grow(age, pos, node, pos_hash)
 		end
 	end
 
 	return true
 end
 
+function kelp.surface_on_construct(pos)
+	local pos_hash = mt_hash_node_position(pos)
+	kelp.init_age(pos, nil, pos_hash)
+	kelp.init_timer(pos, pos_hash)
+end
+
+
 function kelp.surface_on_destruct(pos)
 	local node = mt_get_node(pos)
 	local pos_hash = mt_hash_node_position(pos)
 
 	-- on_falling callback. Activated by pistons for falling nodes too.
 	if kelp.is_falling(pos, node) then
-		kelp.detach_drop(pos, kelp.get_height(node.param2), pos_hash)
+		kelp.detach_drop(pos, node.param2, pos_hash)
 	end
 
+	-- Removes position from queue
+	kelp.age_queue_pos[pos_hash] = nil
+
 	-- Unlocks drops.
 	if kelp.lock_drop > 0 then
 		kelp.lock_drop = kelp.lock_drop - 1
@@ -327,13 +492,14 @@ function kelp.surface_on_destruct(pos)
 end
 
 
+
 function kelp.surface_on_mvps_move(pos, node, oldpos, nodemeta)
 	-- Pistons moving falling nodes will have already activated on_falling callback.
 	kelp.detach_dig(pos, pos, node, mt_get_item_group(node.name, "falling_node") ~= 1)
 end
 
 
--- NOTE: Uncomment this to use ABMs
+-- NOTE: Uncomment this to use ABMs.
 -- local function surface_unsubmerged_abm(pos, node)
 -- 	local dig_pos = find_unsubmerged(pos, node)
 -- 	if dig_pos then
@@ -343,52 +509,6 @@ end
 -- end
 
 
--- NOTE: Uncomment this to use nodetimers
-function kelp.surface_register_nodetimer(pos, node, pos_hash, meta, age)
-	-- Optional params
-	local pos_hash,meta,age = pos_hash,meta,age
-	local timer = kelp.registered_nodetimers[pos_hash]
-
-	if not timer then
-		pos_hash = pos_hash or mt_hash_node_position(pos)
-
-		timer = mt_get_node_timer(pos)
-		kelp.registered_nodetimers[pos_hash] = timer
-
-		-- Pool age to avoid meta:get* operations
-		meta = meta or mt_get_meta(pos)
-		if not age then
-			if not meta:contains("mcl_ocean:kelp_age") then
-				age = math_random(0, kelp.MAX_AGE-1)
-			else
-				age = meta:get_int("mcl_ocean:kelp_age")
-			end
-		end
-		kelp.age_pool[pos_hash] = age
-		meta:set_int("mcl_ocean:kelp_age", age)
-	end
-
-	if not timer:is_started() then
-		timer:start(kelp.TIMER_INTERVAL)
-	end
-
-	return pos_hash, meta, age
-end
-
-
--- NOTE: Uncomment this to use ABMs
--- function kelp.grow_abm(pos, node)
--- 	-- Grow kelp by 1 node length if it would grow inside water
--- 	node.param2 = next_param2(node.param2)
--- 	local pos_tip, node_tip = get_tip(pos, node)
--- 	local def_tip = mt_registered_nodes[node_tip.name]
--- 	if is_submerged(node_tip, def_tip) then
--- 		kelp.next_grow(pos, node, pos_tip, def_tip,
--- 			is_downward_flowing(pos_tip, node_tip, def_tip))
--- 	end
--- end
-
-
 function kelp.kelp_on_place(itemstack, placer, pointed_thing)
 	if pointed_thing.type ~= "node" or not placer then
 		return itemstack
@@ -410,17 +530,18 @@ function kelp.kelp_on_place(itemstack, placer, pointed_thing)
 	-- Protection
 	if mt_is_protected(pos_under, player_name) or
 			mt_is_protected(pos_above, player_name) then
-		minetest.log("action", player_name
+		mt_log("action", player_name
 			.. " tried to place " .. itemstack:get_name()
 			.. " at protected position "
-			.. minetest.pos_to_string(pos_under))
+			.. mt_pos_to_string(pos_under))
-		minetest.record_protection_violation(pos_under, player_name)
+		mt_record_protection_violation(pos_under, player_name)
 		return itemstack
 	end
 
 
 	local pos_tip, node_tip, def_tip
-	local pos_hash, meta
+	local pos_hash = mt_hash_node_position(pos_under)
+	local age = kelp.roll_init_age()
 
 
 	-- Kelp must also be placed on the top/tip side of the surface/kelp
@@ -430,12 +551,9 @@ function kelp.kelp_on_place(itemstack, placer, pointed_thing)
 
 	-- When placed on kelp.
 	if mt_get_item_group(nu_name, "kelp") == 1 then
-		pos_tip, node_tip = kelp.get_tip(pos_under, node_under)
+		pos_tip,node_tip = kelp.get_tip(pos_under, node_under.param2)
 		def_tip = mt_registered_nodes[node_tip.name]
 
-		pos_hash = mt_hash_node_position(pos_under)
-		meta = mt_get_meta(pos_under)
-
 	-- When placed on surface.
 	else
 		local new_kelp = false
@@ -452,18 +570,15 @@ function kelp.kelp_on_place(itemstack, placer, pointed_thing)
 			return itemstack
 		end
 
-		-- NOTE: Uncomment this to use nodetimers
-		-- Register nodetimer
-		pos_hash, meta = kelp.surface_register_nodetimer(pos_under)
-
 		pos_tip = pos_above
 		node_tip = mt_get_node(pos_above)
 		def_tip = mt_registered_nodes[node_tip.name]
 	end
 
 	-- New kelp must also be submerged in water.
-	local downward_flowing = kelp.is_downward_flowing(pos_tip, node_tip, def_tip)
+	local downward_flowing = kelp.is_downward_flowing(pos_tip, node_tip)
-	if not (kelp.is_submerged(node_tip, def_tip) or downward_flowing) then
+	local submerged = kelp.is_submerged(node_tip)
+	if not submerged then
 		return itemstack
 	end
 
@@ -472,19 +587,46 @@ function kelp.kelp_on_place(itemstack, placer, pointed_thing)
 	if def_node.sounds then
 		mt_sound_play(def_node.sounds.place, { gain = 0.5, pos = pos_under }, true)
 	end
-	kelp.next_grow(pos_under, node_under, pos_tip, def_tip, downward_flowing)
+	kelp.next_height(pos_under, node_under, pos_tip, node_tip, def_tip, submerged, downward_flowing)
 	if not mt_is_creative_enabled(player_name) then
 		itemstack:take_item()
 	end
 
-	-- Reroll age
-	local age = math_random(0, kelp.MAX_AGE-1)
-	meta:set_int("mcl_ocean:kelp_age", age)
-	kelp.age_pool[pos_hash] = age
-
 	return itemstack
 end
 
+
+function kelp.lbm_register_nodetimer(pos, node)
+	local pos_hash = mt_hash_node_position(pos)
+	kelp.init_age(pos, nil, pos_hash)
+	kelp.init_timer(pos, pos_hash)
+end
+
+
+local gstep_time = 0
+function kelp.globalstep(dtime)
+	if #kelp.age_queue > kelp.MAX_AGE_QUEUE then
+		kelp.store_meta()
+	end
+
+	gstep_time = gstep_time + dtime
+	if gstep_time < kelp.META_TICK then
+		return
+	end
+	gstep_time = 0
+
+	if #kelp.age_queue > 0 then
+		kelp.store_meta()
+	end
+end
+
+
+function kelp.on_shutdown()
+	if #kelp.age_queue > 0 then
+		kelp.store_meta()
+	end
+end
+
 --------------------------------------------------------------------------------
 -- Kelp registration API
 --------------------------------------------------------------------------------
@@ -526,9 +668,10 @@ kelp.surface_deftemplate = {
 	groups = { dig_immediate = 3, deco_block = 1, plant = 1, kelp = 1, },
 	--sounds = sounds,
 	--node_dig_prediction = nodename,
-	after_dig_node = kelp.surface_after_dig_node,
+	on_construct = kelp.surface_on_construct,
 	on_destruct = kelp.surface_on_destruct,
 	on_dig = kelp.surface_on_dig,
+	after_dig_node = kelp.surface_after_dig_node,
 	on_timer = kelp.surface_on_timer,
 	mesecon = { on_mvps_move = kelp.surface_on_mvps_move, },
 	drop = "", -- drops are handled in on_dig
@@ -573,7 +716,7 @@ function kelp.register_kelp_surface(surface, surface_deftemplate, surface_docs)
 		doc.add_entry_alias("nodes", surface_docs.entry_id_orig, "nodes", surfacename)
 	end
 
-	local sounds = table.copy(def.sounds)
+	local sounds = table_copy(def.sounds)
 	sounds.dig = kelp.leaf_sounds.dig
 	sounds.dug = kelp.leaf_sounds.dug
 	sounds.place = kelp.leaf_sounds.place
@@ -592,9 +735,9 @@ end
 -- Kelp surfaces nodes ---------------------------------------------------------
 
 -- Dirt must be registered first, for the docs
-kelp.register_kelp_surface(kelp.surfaces[1], table.copy(kelp.surface_deftemplate), kelp.surface_docs)
+kelp.register_kelp_surface(kelp.surfaces[1], table_copy(kelp.surface_deftemplate), kelp.surface_docs)
 for i=2, #kelp.surfaces do
-	kelp.register_kelp_surface(kelp.surfaces[i], table.copy(kelp.surface_deftemplate), kelp.surface_docs)
+	kelp.register_kelp_surface(kelp.surfaces[i], table_copy(kelp.surface_deftemplate), kelp.surface_docs)
 end
 
 -- Kelp item -------------------------------------------------------------------
@@ -676,15 +819,18 @@ minetest.register_craft({
 
 -- ABMs ------------------------------------------------------------------------
 
--- NOTE: Uncomment this to use nodetimers
 minetest.register_lbm({
-	label = "Kelp timer registration",
+	label = "Kelp initialise",
-	name = "mcl_ocean:kelp_timer_registration",
+	name = "mcl_ocean:kelp_init",
 	nodenames = { "group:kelp" },
-	run_at_every_load = true, -- so old kelps are also registered
+	run_at_every_load = true, -- so old kelps are also initialised
-	action = kelp.surface_register_nodetimer,
+	action = kelp.lbm_register_nodetimer,
 })
 
+
+minetest.register_globalstep(kelp.globalstep)
+minetest.register_on_shutdown(kelp.on_shutdown)
+
 -- NOTE: Uncomment this to use ABMs
 -- minetest.register_abm({
 -- 	label = "Kelp drops",