1 files changed, 252 insertions, 0 deletions
diff --git a/railcart/railcart.lua b/railcart/railcart.lua
new file mode 100644
index 0000000..917da44
--- /dev/null
+++ b/railcart/railcart.lua
@@ -0,0 +1,252 @@
+RAILCART_ENTITY_UPDATE_TIME = 1
+RAILCART_OBJECT_UPDATE_TIME = 5
+RAILCART_OBJECT_SAVE_TIME = 10
+RAILCART_RELOAD_DISTANCE = 32
+RAILCART_SNAP_DISTANCE = 0.5
+RAILCART_SPEED_MIN = 0.1
+RAILCART_SPEED_MAX = 10
+
+railcart = {
+	timer = 0,
+	allcarts = {},
+}
+
+railcart.cart = {
+	id = nil,
+	entity = {},
+	pos = nil,
+	target = nil,
+	prev = nil,
+	accel = nil,
+	dir = {x=0, y=0, z=0},
+	vel = {x=0, y=0, z=0},
+	acc = {x=0, y=0, z=0},
+	timer = 0,
+}
+
+function railcart.cart:new(obj)
+	obj = obj or {}
+	setmetatable(obj, self)
+	self.__index = self
+	return obj
+end
+
+function railcart.cart:is_loaded()
+	for _, player in pairs(minetest.get_connected_players()) do
+		local pos = player:getpos()
+		if pos then
+			local dist = railtrack:get_distance(pos, self.pos)
+			if dist <= RAILCART_RELOAD_DISTANCE then
+				return true
+			end
+		end
+	end
+	return false
+end
+
+function railcart.cart:on_step(dtime)
+	self.timer = self.timer - dtime
+	if self.timer > 0 then
+		return
+	end
+	self.timer = RAILCART_OBJECT_UPDATE_TIME
+	local entity = railcart:get_cart_ref(self.id)
+	if entity.object then
+		return
+	end
+	if self:is_loaded() then
+		local object = minetest.add_entity(self.pos, "railcart:cart_entity")
+		if object then
+			entity = object:get_luaentity() or {}
+			entity.cart = self
+			object:setvelocity(self.vel)
+			object:setacceleration(self.acc)
+		end
+	else
+		self.timer = railcart:update(self, self.timer)
+	end
+end
+
+function railcart:save()
+	local carts = {}
+	for id, cart in pairs(railcart.allcarts) do
+		local ref = {}
+		for k, v in pairs(cart) do
+			ref[k] = v
+		end
+		ref.entity = nil
+		table.insert(carts, ref)
+	end
+	local output = io.open(minetest.get_worldpath().."/railcart.txt",'w')
+	if output then
+		output:write(minetest.serialize(carts))
+		io.close(output)
+	end
+end
+
+function railcart:get_cart_ref(id)
+	local cart_ref = {}
+	for _, ref in pairs(minetest.luaentities) do
+		if ref.cart then
+			if ref.cart.id == id then
+				cart_ref = ref
+				break
+			end
+		end
+	end
+	return cart_ref
+end
+
+function railcart:get_delta_time(vel, acc, dist)
+	if vel > 0 then
+		if acc == 0 then
+			return dist / vel
+		end
+		local r = math.sqrt(vel * vel + 2 * acc * dist)
+		if r > 0 then
+			return (-vel + r) / acc
+		end
+	end
+	return 9999 --INF
+end
+
+function railcart:velocity_to_dir(v)
+	if math.abs(v.x) > math.abs(v.z) then
+		return {x=railtrack:get_sign(v.x), y=railtrack:get_sign(v.y), z=0}
+	else
+		return {x=0, y=railtrack:get_sign(v.y), z=railtrack:get_sign(v.z)}
+	end
+end
+
+function railcart:velocity_to_speed(vel)
+	local speed = math.max(math.abs(vel.x), math.abs(vel.z))
+	if speed < RAILCART_SPEED_MIN then
+		speed = 0
+	elseif speed > RAILCART_SPEED_MAX then
+		speed = RAILCART_SPEED_MAX
+	end
+	return speed
+end
+
+function railcart:get_target(pos, vel)
+	local meta = minetest.get_meta(vector.round(pos))
+	local dir = self:velocity_to_dir(vel)
+	local targets = {}
+	local rots = RAILTRACK_ROTATIONS
+	local contype = meta:get_string("contype") or ""
+	local s_junc = meta:get_string("junctions") or ""
+	local s_cons = meta:get_string("connections") or ""
+	local s_rots = meta:get_string("rotations") or ""
+	if contype == "section" then
+		local junctions = minetest.deserialize(s_junc) or {}
+		for _, p in pairs(junctions) do
+			table.insert(targets, p)
+		end
+	else
+		local cons = minetest.deserialize(s_cons) or {}
+		for _, p in pairs(cons) do
+			table.insert(targets, p)
+		end
+		if s_rots ~= "" then
+			local fwd = false
+			for _, p in pairs(cons) do
+				if vector.equals(vector.add(pos, dir), p) then
+					fwd = true
+				end
+			end
+			if fwd == true or #cons == 1 then
+				rots = s_rots
+			end
+		end
+	end
+	local rotations = railtrack:get_rotations(rots, dir)
+	for _, r in ipairs(rotations) do
+		for _, t in pairs(targets) do
+			local d = railtrack:get_direction(t, pos)
+			if r.x == d.x and r.z == d.z then
+				return t
+			end
+		end
+	end
+end
+
+function railcart:update(cart, time, object)
+	if object then
+		cart.pos = object:getpos()
+		cart.vel = object:getvelocity()
+	end
+	if not cart.target then
+		cart.pos = vector.new(cart.prev)
+		cart.target = railcart:get_target(cart.pos, cart.vel)
+		if object then
+			object:moveto(cart.pos)
+		end
+	end
+	local speed = railcart:velocity_to_speed(cart.vel)
+	if not cart.target then
+		speed = 0
+	end
+	if speed > RAILCART_SPEED_MIN then
+		cart.dir = railtrack:get_direction(cart.target, cart.pos)
+		local d1 = railtrack:get_distance(cart.prev, cart.target)
+		local d2 = railtrack:get_distance(cart.prev, cart.pos)
+		local dist = d1 - d2
+		if dist > RAILCART_SNAP_DISTANCE then
+			local accel = RAILTRACK_ACCEL_FLAT
+			if cart.dir.y == -1 then
+				accel = RAILTRACK_ACCEL_DOWN
+			elseif cart.dir.y == 1 then
+				accel = RAILTRACK_ACCEL_UP
+			end
+			accel = cart.accel or accel
+			local dt = railcart:get_delta_time(speed, accel, dist)
+			if dt < time then
+				time = dt
+			end
+			local dp = speed * time + 0.5 * accel * time * time
+			local vf = speed + accel * time
+			if object then
+				if vf <= 0 then
+					speed = 0
+					accel = 0
+				end
+				cart.vel = vector.multiply(cart.dir, speed)
+				cart.acc = vector.multiply(cart.dir, accel)
+			elseif dp > 0 then
+				cart.vel = vector.multiply(cart.dir, vf)
+				cart.pos = vector.add(cart.pos, vector.multiply(cart.dir, dp))
+			end
+		else
+			cart.pos = vector.new(cart.target)
+			cart.prev = vector.new(cart.target)
+			cart.accel = railtrack:get_acceleration(cart.target)
+			cart.target = nil
+			return 0
+		end
+	else
+		cart.vel = {x=0, y=0, z=0}
+		cart.acc = {x=0, y=0, z=0}
+	end
+	if object then
+		if cart.dir.y == -1 then
+			object:set_animation({x=1, y=1}, 1, 0)
+		elseif cart.dir.y == 1 then
+			object:set_animation({x=2, y=2}, 1, 0)
+		else
+			object:set_animation({x=0, y=0}, 1, 0)
+		end
+		if cart.dir.x < 0 then
+			object:setyaw(math.pi / 2)
+		elseif cart.dir.x > 0 then
+			object:setyaw(3 * math.pi / 2)
+		elseif cart.dir.z < 0 then
+			object:setyaw(math.pi)
+		elseif cart.dir.z > 0 then
+			object:setyaw(0)
+		end
+		object:setvelocity(cart.vel)
+		object:setacceleration(cart.acc)
+	end
+	return time
+end
+