--[ Head Follow Mouse/Camera ]--

--[ Services ]:

local RunSrv = game:GetService("RunService");

local Wrks = game:GetService("Workspace");
local Plrs = game:GetService("Players");

--[ Pre-Funcs ]:

local Ang = CFrame.Angles;	--[ Storing these as variables so I dont have to type them out. ]
local aSin = math.asin;
local aTan = math.atan;

--[ Constants ]:

local Cam = Wrks.CurrentCamera;

local Plr = Plrs.LocalPlayer;
local Mouse = Plr:GetMouse();
local Body = Wrks:WaitForChild(Plr.Name);
local Head = Body:WaitForChild("Head");
local Hum = Body:WaitForChild("Humanoid");
local Core = Body:WaitForChild("HumanoidRootPart");
local IsR6 = (Hum.RigType.Value==0);	--[ Checking if the player is using the new Rig or the original. ]
local Trso = (IsR6 and Body:WaitForChild("Torso")) or Body:WaitForChild("UpperTorso");
local Neck = (IsR6 and Trso:WaitForChild("Neck")) or Head:WaitForChild("Neck");	--[ Once we know the Rig, we know what to find. ]

local MseGuide = true;	--[ Useful with tools if true; camera tracking runs smoother however. ]
local Fctor = 1;	--[ 0: Negates tracking, 1: Relatively normal tracking, 2: Looks a little weird, just sayin'. ]

local OrgnC0 = Neck.C0;	--[ Get the base C0 to manipulate off of. ]

--[ Setup ]:

Neck.MaxVelocity = 1/3

--[ Activation ]:

coroutine.resume(coroutine.create(function()
	while RunSrv.RenderStepped:wait() and Hum:GetState().Value~=15 do	--[ Adding wait() here is the same as adding wait() later. ]
		local CamCF = Cam.CoordinateFrame
		--local MsePos = Mouse.Origin.p	--[ Might do something with this in a future update... ]
		if ((IsR6 and Body["Torso"]) or Body["UpperTorso"])~=nil and Body["Head"]~=nil then	--[ Check for the Torso and Head... ]
			local TrsoLV = Trso.CFrame.lookVector
			local HdPos = Head.CFrame.p
			if ((IsR6 and Trso["Neck"]) or Head["Neck"])~=nil then	--[ Make sure the Neck still exists. ]
				if Cam.CameraSubject:IsDescendantOf(Body) or Cam.CameraSubject:IsDescendantOf(Plr) then
					local Dist = nil;
					local Diff = nil;
					if not MseGuide then	--[ If not tracking the Mouse then get the Camera. ]
						Dist = (Head.CFrame.p-CamCF.p).magnitude
						Diff = Head.CFrame.Y-CamCF.Y
						if not IsR6 then	--[ R6 and R15 Neck rotation C0s are different; R15: X axis inverted and Z is now the Y. ]
							Neck.C0 = OrgnC0*Ang((aSin(Diff/Dist)*Fctor), -(((HdPos-CamCF.p).Unit):Cross(TrsoLV)).Y, 0)
						else	--[ R15s actually have the properly oriented Neck CFrame. ]
							Neck.C0 = OrgnC0*Ang(-(aSin(Diff/Dist)*Fctor), 0, -(((HdPos-CamCF.p).Unit):Cross(TrsoLV)).Y)
						end
					else
						local _, Point = Wrks:FindPartOnRay(Ray.new(Head.CFrame.p, Mouse.Hit.lookVector), Wrks, false, true)
						Dist = (Head.CFrame.p-Point).magnitude
						Diff = Head.CFrame.Y-Point.Y
						if not IsR6 then
							Neck.C0 = OrgnC0*Ang(-(aTan(Diff/Dist)*Fctor), (((HdPos-Point).Unit):Cross(TrsoLV)).Y*Fctor, 0)
						else
							Neck.C0 = OrgnC0*Ang((aTan(Diff/Dist)*Fctor), 0, (((HdPos-Point).Unit):Cross(TrsoLV)).Y*Fctor)
						end
					end
				end
			end
		end
	end
end))