Give furnace minecart minimum velocity when lit, add train separation code, update logging code, add sequence number to entity staticdata to allow respawn/despawn when carts move when the entity is unloaded

mods/CORE/mcl_util/init.lua

@@ -59,6 +59,15 @@ function mcl_util.mcl_log(message, module, bypass_default_logger)
 		minetest.log(selected_module .. " " .. message)
 	end
 end
+function mcl_util.make_mcl_logger(label, option)
+	-- Return dummy function if debug option isn't set
+	if not minetest.settings:get_bool(option,false) then return function() end, false end
+
+	local label_text = "["..tostring(label).."]"
+	return function(message)
+		mcl_util.mcl_log(message, label_text, true)
+	end, true
+end
 
 local player_timers = {}
 
@@ -1176,6 +1185,9 @@ end
 function mcl_util.get_active_object_id_from_uuid(uuid)
 	return uuid_to_aoid_cache[uuid] or scan_active_objects() or uuid_to_aoid_cache[uuid]
 end
+function mcl_util.get_luaentity_from_uuid(uuid)
+	return minetest.luaentities[ mcl_util.get_active_object_id_from_uuid(uuid) ]
+end
 function mcl_util.get_uuid(obj)
 	local le = obj:get_luaentity()
 

mods/ENTITIES/mcl_minecarts/carts.lua

@@ -3,13 +3,7 @@ local modpath = minetest.get_modpath(modname)
 local mod = mcl_minecarts
 local S = minetest.get_translator(modname)
 
-local LOGGING_ON = minetest.settings:get_bool("mcl_logging_minecarts", false)
-local DEBUG = false
-local function mcl_log(message)
-	if LOGGING_ON then
-		mcl_util.mcl_log(message, "[Minecarts]", true)
-	end
-end
+local mcl_log = mcl_util.make_mcl_logger("mcl_logging_minecarts", "Minecarts")
 
 -- Imports
 local table_merge = mcl_util.table_merge
@@ -53,6 +47,7 @@ local function make_staticdata( railtype, connected_at, dir )
 		velocity = 0,
 		dir = vector.new(dir),
 		mass = 1,
+		seq = 1,
 	}
 end
 
@@ -86,8 +81,15 @@ function DEFAULT_CART_DEF:on_activate(staticdata, dtime_s)
 	if not data.uuid then
 		data.uuid  = mcl_util.get_uuid(self.object)
 	end
+	self._seq = data.seq or 1
+
 	local cd = get_cart_data(data.uuid)
-	if not cd then update_cart_data(data) end
+	if not cd then
+		update_cart_data(data)
+	else
+		if not cd.seq then cd.seq = 1 end
+		data = cd
+	end
 
 	-- Initialize
 	if type(data) == "table" then
@@ -121,7 +123,7 @@ function DEFAULT_CART_DEF:on_activate(staticdata, dtime_s)
 end
 function DEFAULT_CART_DEF:get_staticdata()
 	save_cart_data(self._staticdata.uuid)
-	return minetest.serialize({uuid = self._staticdata.uuid})
+	return minetest.serialize({uuid = self._staticdata.uuid, seq=self._seq})
 end
 
 function DEFAULT_CART_DEF:add_node_watch(pos)
@@ -147,6 +149,15 @@ function DEFAULT_CART_DEF:remove_node_watch(pos)
 	end
 	staticdata.node_watches = new_watches
 end
+function DEFAULT_CART_DEF:get_cart_position()
+	local staticdata = self._staticdata
+
+	if staticdata.connected_at then
+		return staticdata.connected_at + staticdata.dir * staticdata.distance
+	else
+		return self.object:get_pos()
+	end
+end
 function DEFAULT_CART_DEF:on_step(dtime)
 	local staticdata = self._staticdata
 	if not staticdata then
@@ -154,6 +165,11 @@ function DEFAULT_CART_DEF:on_step(dtime)
 		self._staticdata = staticdata
 	end
 
+	if self._seq ~= staticdata.seq then
+		print("TODO: remove cart #"..staticdata.uuid.." with sequence number mismatch")
+		print("self.seq="..tostring(self._seq)..", staticdata.seq="..tostring(staticdata.seq))
+	end
+
 	-- Regen
 	local hp = self.object:get_hp()
 	if hp < MINECART_MAX_HP then

mods/ENTITIES/mcl_minecarts/carts/with_furnace.lua

@@ -73,6 +73,10 @@ mcl_minecarts.register_minecart({
 
 		-- Update furnace stuff
 		if (staticdata.fueltime or 0) > 0 then
+			if staticdata.velocity < 0.25 then
+				staticdata.velocity = 0.25
+			end
+
 			staticdata.fueltime = (staticdata.fueltime or dtime) - dtime
 			if staticdata.fueltime <= 0 then
 				self.object:set_properties({textures =

mods/ENTITIES/mcl_minecarts/init.lua

@@ -5,9 +5,10 @@ local mod = mcl_minecarts
 mcl_minecarts.modpath = modpath
 
 -- Constants
-mcl_minecarts.speed_max = 10
-mcl_minecarts.check_float_time = 15
-mcl_minecarts.FRICTION = 0.4
+mod.speed_max = 10
+mod.check_float_time = 15
+mod.FRICTION = 0.4
+mod.MAX_TRAIN_LENGTH = 4
 
 for _,filename in pairs({"storage","functions","rails","train","carts"}) do
 	dofile(modpath.."/"..filename..".lua")

mods/ENTITIES/mcl_minecarts/movement.lua

@@ -4,8 +4,9 @@ local mod = mcl_minecarts
 local S = minetest.get_translator(modname)
 
 -- Constants
-local DEBUG = false
+local mcl_debug,DEBUG = mcl_util.make_mcl_logger("mcl_logging_minecart_debug", "Minecart Debug")
 local friction = mcl_minecarts.FRICTION
+local MAX_TRAIN_LENGTH = mod.MAX_TRAIN_LENGTH
 
 -- Imports
 local train_length = mod.train_length
@@ -131,6 +132,10 @@ local function handle_cart_collision(cart1, prev_pos, next_dir)
 
 	local meta = minetest.get_meta(vector.add(pos,next_dir))
 	if not cart_uuid then return end
+
+	-- Don't collide with the train car in front of you
+	if cart1._staticdata.ahead == cart_uuid then return end
+
 	minetest.log("action","cart #"..cart1._staticdata.uuid.." collided with cart #"..cart_uuid.." at "..tostring(pos))
 
 	local cart2_aoid = mcl_util.get_active_object_id_from_uuid(cart_uuid)
@@ -146,8 +151,8 @@ local function handle_cart_collision(cart1, prev_pos, next_dir)
 	local m1 = cart1_staticdata.mass
 	local m2 = cart2_staticdata.mass
 
-	print("u1="..tostring(u1)..",u2="..tostring(u2))
-	if u2 == 0 and u1 < 4 and train_length(cart1) < 3 then
+	--print("u1="..tostring(u1)..",u2="..tostring(u2))
+	if u2 == 0 and u1 < 4 and train_length(cart1) < MAX_TRAIN_LENGTH then
 		link_cart_ahead(cart1, cart2)
 		cart2_staticdata.dir = mcl_minecarts:get_rail_direction(cart2_staticdata.connected_at, cart1_staticdata.dir)
 		cart2_staticdata.velocity = cart1_staticdata.velocity
@@ -275,7 +280,7 @@ local function do_movement_step(self, dtime)
 	end
 
 	if DEBUG and ( v_0 > 0 or a ~= 0 ) then
-		print( "    cart "..tostring(staticdata.uuid)..
+		mcl_debug("    cart "..tostring(staticdata.uuid)..
 		       ": a="..tostring(a)..
 		        ",v_0="..tostring(v_0)..
 		        ",x_0="..tostring(x_0)..
@@ -334,7 +339,7 @@ local function do_movement_step(self, dtime)
 	staticdata.distance = x_1
 
 	if DEBUG and (1==0) and ( v_0 > 0 or a ~= 0 ) then
-		print( "-   cart #"..tostring(staticdata.uuid)..
+		mcl_debug( "-   cart #"..tostring(staticdata.uuid)..
 		       ": a="..tostring(a)..
 		        ",v_0="..tostring(v_0)..
 		        ",v_1="..tostring(v_1)..
@@ -362,7 +367,7 @@ local function do_movement_step(self, dtime)
 		-- Get the next direction
 		local next_dir,_ = mcl_minecarts:get_rail_direction(pos, staticdata.dir, nil, nil, staticdata.railtype)
 		if DEBUG and next_dir ~= staticdata.dir then
-			print( "Changing direction from "..tostring(staticdata.dir).." to "..tostring(next_dir))
+			mcl_debug( "Changing direction from "..tostring(staticdata.dir).." to "..tostring(next_dir))
 		end
 
 		-- Handle cart collisions
@@ -376,7 +381,7 @@ local function do_movement_step(self, dtime)
 
 		-- Handle end of track
 		if next_dir == staticdata.dir * -1 and next_dir.y == 0 then
-			if DEBUG then print("Stopping cart at end of track at "..tostring(pos)) end
+			if DEBUG then mcl_debug("Stopping cart at end of track at "..tostring(pos)) end
 			staticdata.velocity = 0
 		end
 
@@ -384,7 +389,7 @@ local function do_movement_step(self, dtime)
 		staticdata.dir = next_dir
 	elseif stops_in_block and v_1 < (friction/5) and a <= 0 then
 		-- Handle direction flip due to gravity
-		if DEBUG then print("Gravity flipped direction") end
+		if DEBUG then mcl_debug("Gravity flipped direction") end
 
 		-- Velocity should be zero at this point
 		staticdata.velocity = 0
@@ -405,7 +410,7 @@ local function do_movement_step(self, dtime)
 
 	-- Debug reporting
 	if DEBUG and ( v_0 > 0 or v_1 > 0 ) then
-		print( "    cart #"..tostring(staticdata.uuid)..
+		mcl_debug( "    cart #"..tostring(staticdata.uuid)..
 		       ": a="..tostring(a)..
 		        ",v_0="..tostring(v_0)..
 		        ",v_1="..tostring(v_1)..

mods/ENTITIES/mcl_minecarts/train.lua

@@ -4,7 +4,9 @@ local mod = mcl_minecarts
 
 -- Imports
 local get_cart_data = mod.get_cart_data
+local MAX_TRAIN_LENGTH = mod.MAX_TRAIN_LENGTH
 
+-- Follow .behind to the back end of a train
 local function find_back(start)
 	while start.behind do
 		local nxt = get_cart_data(start.behind)
@@ -14,10 +16,13 @@ local function find_back(start)
 	return start
 end
 
+-- Iterate across all the cars in a train
 local function train_cars(anchor)
 	local back = find_back(anchor._staticdata)
+	local limit = MAX_TRAIN_LENGTH
 	return function()
-		if not back then return end
+		if not back or limit <= 0 then return end
+		limit = limit - 1
 
 		local ret = back
 		if back.ahead then
@@ -28,26 +33,6 @@ local function train_cars(anchor)
 		return ret
 	end
 end
-
-function mod.update_train(cart)
-	local sum_velocity = 0
-	local count = 0
-	for cart in train_cars(cart) do
-		count = count + 1
-		sum_velocity = sum_velocity + (cart.velocity or 0)
-	end
-	local avg_velocity = sum_velocity / count
-	if count == 0 then return end
-
-	print("Using velocity "..tostring(avg_velocity))
-
-	-- Set the entire train to the average velocity
-	for c in train_cars(cart) do
-		print(tostring(c.behind).."->"..c.uuid.."->"..tostring(c.ahead).."  setting cart #"..c.uuid.." velocity to "..tostring(avg_velocity))
-		c.velocity = avg_velocity
-	end
-end
-
 function mod.train_length(cart)
 	local count = 0
 	for cart in train_cars(cart) do
@@ -55,6 +40,68 @@ function mod.train_length(cart)
 	end
 	return count
 end
+
+function mod.is_in_same_train(anchor, other)
+	for cart in train_cars(anchor) do
+		if cart.uuid == other.uuid then return true end
+	end
+	return false
+end
+
+function mod.distance_between_cars(car1, car2)
+	if not car1.connected_at then return nil end
+	if not car2.connected_at then return nil end
+
+	if not car1.dir then car1.dir = vector.zero() end
+	if not car2.dir then car2.dir = vector.zero() end
+
+	local pos1 = vector.add(car1.connected_at, vector.multiply(car1.dir, car1.distance))
+	local pos2 = vector.add(car2.connected_at, vector.multiply(car2.dir, car2.distance))
+
+	return vector.distance(pos1, pos2)
+end
+local distance_between_cars = mod.distance_between_cars
+
+function mod.update_train(cart)
+	local staticdata = cart._staticdata
+
+	-- Only update from the back
+	if staticdata.behind or not staticdata.ahead then return end
+	print("\nUpdating train")
+
+	-- Do no special processing if the cart is not part of a train
+	if not staticdata.ahead and not staticdata.behind then return end
+
+	-- Calculate the average velocity of all train cars
+	local sum_velocity = 0
+	for cart in train_cars(cart) do
+		if cart.velocity or 0 > velocity then
+			velocity = cart.velocity
+		end
+	end
+	print("Using velocity "..tostring(velocity))
+
+	-- Set the entire train to the average velocity
+	local behind = nil
+	for c in train_cars(cart) do
+		local e = 0
+		local separation
+		if behind then
+			separation = distance_between_cars(behind, c)
+			local e = 0
+			if separation > 1.25 then
+				velocity = velocity * 0.9
+			elseif separation < 1.15 then
+				velocity = velocity * 1.1
+			end
+		end
+		print(tostring(c.behind).."->"..c.uuid.."->"..tostring(c.ahead).."("..tostring(separation)..")  setting cart #"..c.uuid.." velocity to "..tostring(velocity))
+		c.velocity = velocity
+
+		behind = c
+	end
+end
+
 function mod.link_cart_ahead(cart, cart_ahead)
 	local staticdata = cart._staticdata
 	local ca_staticdata = cart_ahead._staticdata
@@ -64,9 +111,3 @@ function mod.link_cart_ahead(cart, cart_ahead)
 	staticdata.ahead = ca_staticdata.uuid
 	ca_staticdata.behind = staticdata.uuid
 end
-function mod.is_in_same_train(anchor, other)
-	for cart in train_cars(anchor) do
-		if cart.uuid == other.uuid then return true end
-	end
-	return false
-end