init.lua

local get_connected_players = minetest.get_connected_players
local lastdir = {}
local basepos = vector.new(0, 6.35, 0)

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", {
				-- The position attr makes headanim work on older clients
				-- https://github.com/LoneWolfHT/headanim/pull/4
				position = {
					vec = basepos,
					absolute = true
				},
				rotation = {
					vec = {x = ldeg, y = 0, z = 0},
					interpolation = 0.09,
				}
			})
		end
	end
end)

minetest.register_on_leaveplayer(function(player)
	lastdir[player:get_player_name()] = nil
end)