VoxeLibre/mods/ENTITIES/mcl_mobs/api/mob_functions/head_logic.lua

local math = math
local vector = vector

--converts yaw to degrees
local degrees = function(yaw)
	return yaw*180.0/math.pi
end

mobs.do_head_logic = function(self,dtime)

	local player = minetest.get_player_by_name("singleplayer")

	local look_at = player:get_pos()
	look_at.y = look_at.y + player:get_properties().eye_height

	local pos = self.object:get_pos()

	local body_yaw = self.object:get_yaw()

	local body_dir = minetest.yaw_to_dir(body_yaw)

	pos.y = pos.y + self.head_height_offset

	local head_offset = vector.multiply(body_dir, self.head_direction_offset)

	pos = vector.add(pos, head_offset)

	minetest.add_particle({
		pos = pos,
		velocity = {x=0, y=0, z=0},
		acceleration = {x=0, y=0, z=0},
		expirationtime = 0.2,
		size = 1,
		texture = "default_dirt.png",
	})

	local bone_pos = vector.new(0,0,0)

	--(horizontal)
	bone_pos.y = self.head_bone_pos_y

	--(vertical)
	bone_pos.z = self.head_bone_pos_z

	--print(yaw)

	--local _, bone_rot = self.object:get_bone_position("head")

	--bone_rot.x = bone_rot.x + (dtime * 10)
	--bone_rot.z = bone_rot.z + (dtime * 10)

	local head_yaw = minetest.dir_to_yaw(vector.direction(pos,look_at)) - body_yaw

	if self.reverse_head_yaw then
		head_yaw = head_yaw * -1
	end

	--over rotation protection
	--stops radians from going out of spec
	if head_yaw > math.pi then
		head_yaw = head_yaw - (math.pi * 2)
	elseif head_yaw < -math.pi then
		head_yaw = head_yaw + (math.pi * 2)
	end


	local check_failed = false
	--upper check + 90 degrees or upper math.radians (3.14/2)
	if head_yaw > math.pi - (math.pi/2) then
		head_yaw = 0
		check_failed = true
	--lower check - 90 degrees or lower negative math.radians (-3.14/2)
	elseif head_yaw < -math.pi + (math.pi/2) then
		head_yaw = 0
		check_failed = true
	end

	local head_pitch = 0

	--DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG
	--head_yaw = 0
	--DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG DEBUG

	if not check_failed then
		head_pitch = minetest.dir_to_yaw(vector.new(vector.distance(vector.new(pos.x,0,pos.z),vector.new(look_at.x,0,look_at.z)),0,pos.y-look_at.y))+(math.pi/2)
	end

	if self.head_pitch_modifier then
		head_pitch = head_pitch + self.head_pitch_modifier
	end

	if self.swap_y_with_x then
		self.object:set_bone_position(self.head_bone, bone_pos, vector.new(degrees(head_pitch),degrees(head_yaw),0))
	else
		self.object:set_bone_position(self.head_bone, bone_pos, vector.new(degrees(head_pitch),0,degrees(head_yaw)))
	end
	--set_bone_position([bone, position, rotation])
end