Help with arm aiming at position

[Sarlex0 (Sarlex)]

So I am trying to make player’s arm to point at mouse position, but my script doesn’t really work.
Video with the issue:
robloxapp-20220812-1158370.wmv (1.2 MB)
For some reason it moves with whole player and even the player is not really looking at mouse’s position and I have no idea why. If anyone can explain why is it happeing and/or suggest way to fix it would be great.
Script I am surrently using for my hand:

repeat wait(0.5) until game:IsLoaded()
local player = game.Players.LocalPlayer
local char = player.Character or game.Players.LocalPlayer.CharacterAdded:Wait()
local RightShoulder = char:WaitForChild("RightUpperArm")
local wpEquipped = false

script.Parent.Equipped:Connect(function()
	wpEquipped = true
end)

script.Parent.Unequipped:Connect(function()
	wpEquipped = false
end)

local function lookDirection()
	if wpEquipped == true then
		RightShoulder.CFrame = CFrame.lookAt(RightShoulder.Position, player:GetMouse().Hit.Position)
	end
end

game["Run Service"].Heartbeat:Connect(lookDirection)

[Daw588]

You can’t just use CFrame in this way to change the position or rotation of the arm. This is because the arm is attached via a joint, and attempting to modify CFrame directly will almost always cause problems like this, and therefore you should directly modify the C0/C1 CFrame of the joint which will require some mathematics like inverse kinematics (IK) to find out what value will rotate and/or move the joint to desired position.

“Inverse kinematics is the use of kinematic equations to determine the motion of a robot to reach a desired position. For example, to perform automated bin picking, a robotic arm used in a manufacturing line needs precise motion from an initial position to a desired position between bins and manufacturing machines.” - What Is Inverse Kinematics? - MATLAB & Simulink

Here are some resources to get you started with IK:

Program your own IK (Inverse Kinematics)

Hello developers!!! I saw that on Roblox there are some posts about Inverse Kinematics, but anyone explaining what or how it is done, so that’s what I come here for. To understand this tutorial you will need a basic knowledge of vectors. If you don’t have it please check this post. What is Inverse Kinematics? Inverse Kinematics (IK) is a process that we are going to apply on a chain of bones to get them to position themselves in such a way that they reach a target point. What does this mean…

CCDIKController - Alternate inverse kinematics method for Motor6D rigs

Hello there, I’m @dthecoolest and this is my third open-source project which I made to contribute back to the community. Credit One of the main reason this project is open-source, couldn’t have done it without them: @JohnathonSelstad - Blogger who posted the tutorial of Psuedo-Code of CCDIK check out the inverse kinematics on his website on GitHub it’s very cool. @EgoMoose - The rotation between two vectors trick really come in useful and helped when translating Unity code to lua code. Robl…

IKB - Inverse Kinematics Bundle

[image] [image] IKB Simple, Lightweight, and Performant IK Bundle About As the name implies, it’s an I nverse K inematics B undle, containing modules for common IK implementations, currently supporting R6 and R15 rigs, with more coming soon! Purpose Makes IK simple and easy to implement for common use cases with little to no knowledge about the math and logic behind the library itself, as well as keeping itself lightweight, and causing little to no impact on t…

[Sarlex0 (Sarlex)]

Isn’t there a simpler way to reach my goal? Like don’t get me wrong everything you just sent is amazing and I read it all, but it really seems rather complicated and advanced unlike what I am trying to do. This “inverse kinematics” are for advanced hand movement with multiple parts working together, but I just need the whole arm to rotate around the shoulder axis

[Daw588]

@Sarlex0

I just need the whole arm to rotate around the shoulder axis

How about this? It apparently solves the problem on Y-axis, you could probably modify to work on all 3 axis.

How would I make a players arm move depending on the y axis of the mouse? (R6)

@mrkomps @johncena12345678953 Sorry for reply. I used mrkomps script and I changed for all clients and looks something like this sorry for the lag *Local script* local Camera = game.Workspace.CurrentCamera local Player = game.Players.LocalPlayer local char = Player.Character local origRightS = char:WaitForChild("Torso"):WaitForChild("Right Shoulder").C0 local origLeftS = char:WaitForChild("Torso"):WaitForChild("Left Shoulder").C0 local origNeck = char:WaitForChild("Torso"):WaitF…

[Sarlex0 (Sarlex)]

Since what you sent is made for R6 models, I have rewritten it to be R15 instead, but it really seems it was not made to support R15 because the character doesnt really look the way I want:
robloxapp-20220812-1333478.wmv (599.1 KB)
I dont really understand the math in this script so maybe I overlooked something important that makes the character look somewhere else. If you care enough, you can read my “changed” script:

repeat wait(0.5) until game:IsLoaded()
local replicated = game:GetService("ReplicatedStorage")
local player = game.Players.LocalPlayer
local char = player.Character or game.Players.LocalPlayer.CharacterAdded:Wait()
local origRightS = char:WaitForChild("RightUpperArm"):WaitForChild("RightShoulder").C0
local origLeftS = char:WaitForChild("LeftUpperArm"):WaitForChild("LeftShoulder").C0
local origNeck = char:WaitForChild("Head"):WaitForChild("Neck").C0
local wpEquipped = false
local m = player:GetMouse()

script.Parent.Equipped:Connect(function()
	wpEquipped = true
end)

script.Parent.Unequipped:Connect(function()
	wpEquipped = false
end)


local function lookDirection()
	if wpEquipped == true then
		if char.RightUpperArm:FindFirstChild("RightShoulder") then
			char.RightUpperArm["RightShoulder"].C0 = char.RightUpperArm["RightShoulder"].C0:Lerp(CFrame.new(1, .65, 0) * CFrame.Angles(-math.asin((m.Origin.p - m.Hit.p).unit.y), 1.55, 0, 0) , 0.1)
		end
		if char.LeftUpperArm:FindFirstChild("LeftShoulder") then
			char.LeftUpperArm["LeftShoulder"].C0 = char.LeftUpperArm["LeftShoulder"].C0:Lerp(CFrame.new(-1, .65, 0) * CFrame.Angles(-math.asin((m.Origin.p - m.Hit.p).unit.y), -1.55, 0, 0) , 0.1)
		end
		if char.Head:FindFirstChild("Neck") then
			char.Head["Neck"].C0 = char.Head["Neck"].C0:Lerp(CFrame.new(0, 1, 0) * CFrame.Angles(-math.asin((m.Origin.p - m.Hit.p).unit.y) + 1.55, 3.15, 0), 0.2)
		end
	else
		if char.RightUpperArm:FindFirstChild("RightShoulder") then
			char.RightUpperArm["RightShoulder"].C0 = char.RightUpperArm["RightShoulder"].C0:lerp(origRightS, 0.1)
		end

		if char.LeftUpperArm:FindFirstChild("LeftShoulder") then
			char.LeftUpperArm["LeftShoulder"].C0 = char.LeftUpperArm["LeftShoulder"].C0:lerp(origLeftS, 0.1)
		end

		if char.Head:FindFirstChild("Neck") then
			char.Head["Neck"].C0 = char.Head["Neck"].C0:lerp(origNeck, 0.1)

		end
	end
end

replicated.RemoteEvent.Look.OnClientEvent:Connect(function(PlrAgain, neckCFrame, RsCFrame, LsCFrame)
	local Neck = PlrAgain.Character.Head:FindFirstChild("Neck", true)
	local Rs = PlrAgain.Character.RightUpperArm:FindFirstChild("RightShoulder", true)
	local Ls = PlrAgain.Character.LeftUpperArm:FindFirstChild("LeftShoulder", true)

	if Neck then
		Neck.C0 = neckCFrame
	end

	if Rs then
		Rs.C0 = RsCFrame
	end

	if Ls then
		Ls.C0 = LsCFrame
	end
end)

game["Run Service"].RenderStepped:Connect(lookDirection)

while wait(0.5) do 
	replicated.RemoteEvent.Look:FireServer(char.Head["Neck"].C0, char.RightUpperArm["RightShoulder"].C0, char.LeftUpperArm["LeftShoulder"].C0)
end

[Daw588]

Yeah, I am unsure. But using my IKB resource as mentioned earlier, it does the job without a problem.

local Players = game:GetService("Players")
local Player = Players.LocalPlayer

local R15ALIK = require(script.IKB.R15.AL)

local Character = Player.Character or Player.CharacterAdded:Wait()
local UpperTorso = Character:WaitForChild("UpperTorso")
local Mouse = Player:GetMouse()

local RightArmIK = R15ALIK.new(Character, "Right", "Arm")

Mouse.Move:Connect(function()
	RightArmIK:Solve(Mouse.Hit.Position)
end)

-- Make sure to use RightArmIK:Destroy() once you're done using :Solve() function

Here is an example: IKB-Point-Arm-Towards-Mouse.rbxl (40.5 KB)

[Sarlex0 (Sarlex)]

It works great, but even when I call “RightArmIK:Destroy()” on tool unequip the right hand still remains in the last position, how do I fix that?

[Daw588]

My fault! I forgot to restore the original CFrame of joints when :Destroy() method is called. That was IKB resource issue.

IKB-Point-Arm-Towards-Mouse.rbxl (40.5 KB)

Simply replace the IKB folder with the one here.

[Sarlex0 (Sarlex)]

This works perfectly! One last thing, is there a way to limit player from pointing his arm to certain angles? Or do I have to manullay check if mouse position is too much behind players torso and manually stop the arm movement?

[Daw588]

You could limit/clamp the numbers that you are putting into :Solve() function. I am not really sure.

[Sarlex0 (Sarlex)]

Hold on another thing popped up, the arm now returns to its previous position, but when I then select the tool again, its broken again:
robloxapp-20220812-1456514.wmv (966.3 KB)

[Daw588]

Create the IK with .new() when equipping the tool.

IKB-Point-Arm-Towards-Mouse.rbxl (41.1 KB)

[Sarlex0 (Sarlex)]

oh I forgot Anyways it works now with no problems, I will try to work out those limits for hand rotation, but the most important thing works now thanks to you. I really appriciate your help, you are a great person. Have a great day

[srpskic (Pernato_KokodrkaIo)]

When i use :Destroy() it makes arms stay in their last position, how can I reset their position?

[Daw588]

You can try playing with some of the Motor6D properties:

local obj = put your IKInstance here

obj._UpperJoint.Transform = CFrame.identity
obj._LowerJoint.Transform = CFrame.identity

obj._UpperJoint.C0 = Vector3.zero
obj._LowerJoint.C0 = Vector3.zero