Fix train collision and coupling on opposing trains, and try to implement animation (currently does not work)

helpers.lua

@@ -219,4 +219,7 @@ function advtrains.get_real_index_position(path, index)
 end
 function advtrains.pos_median(pos1, pos2)
 	return {x=pos1.x-(pos1.x-pos2.x)*0.5, y=pos1.y-(pos1.y-pos2.y)*0.5, z=pos1.z-(pos1.z-pos2.z)*0.5}
+end
+function advtrains.abs_ceil(i)
+	return math.ceil(math.abs(i))*math.sign(i)
 end

trainhud.lua

@@ -33,8 +33,8 @@ function advtrains.hud_train_format(train, flip)
 	if flip then fct=-1 end
 	if not train then return "" end
 	local max=advtrains.all_traintypes[train.traintype].max_speed or 10
-	local vel=math.ceil(train.velocity)*fct
-	local tvel=math.ceil(train.tarvelocity)*fct
+	local vel=advtrains.abs_ceil(train.velocity)*fct
+	local tvel=advtrains.abs_ceil(train.tarvelocity)*fct
 	local firstLine, secondLine
 	if vel<0 then
 		firstLine="Speed: <"..string.rep("_", vel+max)..string.rep("+", -vel).."|"..string.rep("_", max)..">"

trainlogic.lua

@@ -574,16 +574,18 @@ function advtrains.try_connect_trains_and_check_collision(id1, id2)
 		for i=(advtrains.get_train_end_index(train2)+0.5),train2.index-0.5 do
 			local testpos=advtrains.get_real_index_position(train2.path,i)
 			if vector.distance(testpos, backpos1) < 0.5 then
+				local v2_sign = math.sign(i - ((train2.index-0.5) - ( (train2.index-0.5)-(advtrains.get_train_end_index(train2)+0.5) / 2 )))
 				--TODO physics
 				train1.velocity=1
-				train2.velocity=-1
+				train2.velocity=v2_sign
 				train1.recently_collided_with_env=true
 				train2.recently_collided_with_env=true
 				return
 			end
 			if vector.distance(testpos, frontpos1) < 0.5 then
+				local v2_sign = math.sign(i - ((train2.index-0.5) - ( (train2.index-0.5)-(advtrains.get_train_end_index(train2)+0.5) / 2 )))
 				train1.velocity=-1
-				train2.velocity=1
+				train2.velocity=v2_sign
 				train1.recently_collided_with_env=true
 				train2.recently_collided_with_env=true
 				return
@@ -680,7 +682,7 @@ function advtrains.invert_train(train_id)
 	
 	local old_path=advtrains.get_or_create_path(train_id, train)
 	train.path={}
-	train.index= - advtrains.get_train_end_index(train1)
+	train.index= - advtrains.get_train_end_index(train)
 	train.velocity=-train.velocity
 	train.tarvelocity=-train.tarvelocity
 	for k,v in pairs(old_path) do

wagons.lua

@@ -268,6 +268,9 @@ function wagon:on_step(dtime)
 		self.object:setvelocity(velocityvec)
 		self.object:setyaw(yaw)
 		self.updatepct_timer=2
+		if self.update_animation then
+			self:update_animation(gp.velocity)
+		end
 	end
 	
 	self.old_velocity_vector=velocityvec
@@ -336,6 +339,11 @@ advtrains.register_wagon("greenwagon", "steam",{textures = {"green.png"}})
 advtrains.register_wagon("redwagon", "steam",{textures = {"red.png"}})
 advtrains.register_wagon("yellowwagon", "steam",{textures = {"yellow.png"}})
 ]]
+
+--[[
+	wagons can define update_animation(self, velocity) if they have a speed-dependent animation
+	this function will be called when the velocity vector changes or every 2 seconds.
+]]
 advtrains.register_wagon("newlocomotive", "steam",{
 	mesh="newlocomotive.b3d",
 	textures = {"advtrains_newlocomotive.png"},
@@ -345,6 +353,12 @@ advtrains.register_wagon("newlocomotive", "steam",{
 	visual_size = {x=1, y=1},
 	wagon_span=1.85,
 	collisionbox = {-1.0,-0.5,-1.0, 1.0,2.5,1.0},
+	update_animation=function(self, velocity)
+		if self.old_anim_velocity~=advtrains.abs_ceil(velocity) then
+			self.object:set_animation({x=1,y=60}, math.floor(velocity))
+			self.old_anim_velocity=advtrains.abs_ceil(velocity)
+		end
+	end
 })
 advtrains.register_wagon("wagon_default", "steam",{
 	mesh="wagon.b3d",