From d3b4a579c60cb6cb16e920e98ba79448bf5a9b8b Mon Sep 17 00:00:00 2001
From: teknomunk <teknomunk@protonmail.com>
Date: Thu, 12 Sep 2024 08:28:34 -0500
Subject: [PATCH] Calculate acceleration of trains based on average of
 acceleration for all carts in the train, make velocity not change on slopes
 and 45 degree track

---
 mods/ENTITIES/mcl_minecarts/movement.lua | 19 +++++++++++++++++--
 mods/ENTITIES/mcl_minecarts/train.lua    |  4 +++-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/mods/ENTITIES/mcl_minecarts/movement.lua b/mods/ENTITIES/mcl_minecarts/movement.lua
index b60fbfe25..e0fb8f22f 100644
--- a/mods/ENTITIES/mcl_minecarts/movement.lua
+++ b/mods/ENTITIES/mcl_minecarts/movement.lua
@@ -305,8 +305,23 @@ local function do_movement_step(staticdata, dtime)
 	-- Calculate timestep remaiing in this block
 	local x_0 = staticdata.distance or 0
 	local remaining_in_block = 1 - x_0
-	local a = calculate_acceleration(staticdata)
+
+	-- Calculate acceleration
 	local v_0 = staticdata.velocity
+	local a = 0
+	if staticdata.ahead or staticdata.behind then
+		-- Calculate acceleration of the entire train
+		local count = 0
+		for cart in mod.train_cars(staticdata) do
+			count = count + 1
+			if cart.behind then
+				a = a + calculate_acceleration(cart)
+			end
+		end
+		a = a / count
+	else
+		a = calculate_acceleration(staticdata)
+	end
 
 	-- Repel minecarts
 	local away = direction_away_from_players(staticdata)
@@ -370,7 +385,7 @@ local function do_movement_step(staticdata, dtime)
 	end
 
 	-- Calculate x_1
-	local x_1 = x_0 + timestep * v_0 + 0.5 * a * timestep * timestep
+	local x_1 = x_0 + (timestep * v_0 + 0.5 * a * timestep * timestep) / vector.length(staticdata.dir)
 
 	-- Update position and velocity of the minecart
 	staticdata.velocity = v_1
diff --git a/mods/ENTITIES/mcl_minecarts/train.lua b/mods/ENTITIES/mcl_minecarts/train.lua
index aab26fcc9..c21cbb0eb 100644
--- a/mods/ENTITIES/mcl_minecarts/train.lua
+++ b/mods/ENTITIES/mcl_minecarts/train.lua
@@ -20,7 +20,7 @@ local function find_back(start)
 end
 
 -- Iterate across all the cars in a train
-local function train_cars(staticdata)
+function mod.train_cars(staticdata)
 	assert(staticdata)
 
 	local back = find_back(staticdata)
@@ -38,6 +38,8 @@ local function train_cars(staticdata)
 		return ret
 	end
 end
+local train_cars = mod.train_cars
+
 function mod.train_length(cart)
 	local count = 0
 	for cart in train_cars(cart) do