Use new set_bone_override() method (Credit: rudzik8)

.luacheckrc

@@ -0,0 +1,45 @@
+read_globals = {
+    "DIR_DELIM", "INIT",
+
+    "minetest", "core",
+    "dump", "dump2",
+
+    "Raycast",
+    "Settings",
+    "PseudoRandom",
+    "PerlinNoise",
+    "VoxelManip",
+    "SecureRandom",
+    "VoxelArea",
+    "PerlinNoiseMap",
+    "PcgRandom",
+    "ItemStack",
+    "AreaStore",
+
+    "vector",
+
+    table = {
+        fields = {
+            "copy",
+            "indexof",
+            "insert_all",
+            "key_value_swap",
+            "shuffle",
+        }
+    },
+
+    string = {
+        fields = {
+            "split",
+            "trim",
+        }
+    },
+
+    math = {
+        fields = {
+            "hypot",
+            "sign",
+            "factorial"
+        }
+    },
+}

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2020 LoneWolfHT
+Copyright (c) 2020-2021 LoneWolfHT
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

init.lua

@@ -1,5 +1,23 @@
-minetest.register_globalstep(function(dtime)
-	for _, player in pairs(minetest.get_connected_players()) do
-		player:set_bone_position("Head", vector.new(0, 6.35, 0), vector.new(-math.deg(player:get_look_vertical()), 0, 0))
+local get_connected_players = minetest.get_connected_players
+local lastdir = {}
+
+minetest.register_globalstep(function()
+	for _, player in pairs(get_connected_players()) do
+		local pname = player:get_player_name()
+		local ldeg = -player:get_look_vertical()
+
+		if (lastdir[pname] or 0) ~= ldeg then
+			lastdir[pname] = ldeg
+			player:set_bone_override("Head", {
+				rotation = {
+					vec = {x = ldeg, y = 0, z = 0},
+					interpolation = 0.14,
+				}
+			})
+		end
 	end
 end)
+
+minetest.register_on_leaveplayer(function(player)
+	lastdir[player:get_player_name()] = nil
+end)

mod.conf

@@ -1 +1,3 @@
 name = headanim
+depends = player_api
+min_minetest_version = 5.9