Client Replication 101. The guide to replicating effects to clients

Alright guys, I’m gonna teach you all reading this how to replicate effects to the client, because YouTube doesn’t teach this, and there are barely any tutorials on it here.

So what is client replication?
Client replication is when you replicate an effect from the server to all clients, decreasing server load.

Why should i use client replication?
Because doing server sided effects is a crime. Server sided VFX not only increases server load but also increases ping tremendously. Don’t believe me? Make a server sided VFX script, turn on data and look at your ping once you use a move. Now imagine that but with 10+ players using a move at the same time. Yeah, no ones gonna play that game. Server sided effects are much less of a hassle, hence why more than 75% of the tutorials on YouTube use server sided effects.

Ok, now i know why i should use Client replication, but how does it work?
So step one, a player will fire a remote event, and the server will receive it.
The red hexagon is the server, and the black circles are the players.


Then the server will be like “Yo, imma send this info to all the clients so i dont get hurt” then the server will use :FireAllClients() to replicate the effect to all the clients.

the next vincent van goh

but now wouldn’t all the vfx be placed differently? Well heres where the real scripting begins.

Firstly create a local script to detect inputs.

local uis = game:GetService("UserInputService")
local rem = Your Path to the remote
local plr = game.Players.LocalPlayer -- you the player
local char = plr.Character or plr.CharacterAdded:Wait() -- your character
local hum = char:WaitForChild("Humanoid") -- your humanoid
uis.InputBegan:Connect(function(inp, typing)
if typing or hum.Health == 0 then return end -- if you are typing or ur humanoids is ded

if inp.KeyCode == Enum.KeyCode.R then -- if you click R
  rem:FireServer() -- fire an event to the server
  end
end)

and thats your local script until now!

next in your server script

local rem = pathToRem -- path to your remote that you fired
rem.OnServerEvent:Connect(function(plr) -- when you recieve the remote with the player that fired it
local char = plr.Character 
local hrp = char:WaitForChild("HumanoidRootPart")

end)

NOW PAUSEEEEEE
We gotta create something to replicate.

Just replicating to client

We will be replicating this effect
Magma on ground mesh
image
Place that effect, or a chosen effect into wherever you want, preferably replicated storage.
now back to scripting
in our server script we are going to add a few values to send to the client to replicate.

local rem = script.Parent

rem.OnServerEvent:Connect(function(plr) -- when you recieve the remote with the player that fired it
	local char = plr.Character 
	local hrp = char:WaitForChild("HumanoidRootPart")
	local positiontospawntheeffect = hrp.CFrame * CFrame.new(0, -2.9, 0)  -- the default height of a hrp is 3 so 2.9 shud position the effect right on the ground without raycast
	local sizeTweenInformation = {Size = Vector3.new(12, 1, 12)} -- the end goal size
	rem:FireAllClients(positiontospawntheeffect, sizeTweenInformation) -- we send the position to all the clients
end)

now back in out local script, we are also going to add a few things

--// shortcuts
local rs = game:GetService("ReplicatedStorage")
local ts = game:GetService("TweenService")
local ti = TweenInfo.new(1, Enum.EasingStyle.Quad, Enum.EasingDirection.InOut)
--//

--// replication function
rem.OnClientEvent:Connect(function(Cframe, endGoal)
	local effect = rs.MagmaOnGround:Clone() -- clone ur effect 
	effect.Anchored = true -- anchor the effect cant move
	effect.CanCollide = false -- can collide off so you cant collide with the object
	effect.CFrame = Cframe -- the position identified in the server script
	effect.Size = Vector3.new(0,0,0) -- starter size
	effect.Parent = workspace -- parent the effect to workspace
	game:GetService("Debris"):AddItem(effect, 4) -- add the item for 4 secs
	ts:Create(effect, ti, endGoal):Play() -- play the tween from the info specified in the server script
	task.wait(2) -- wait a bit
	ts:Create(effect, ti, {Size = Vector3.new(0,0,0)}):Play() -- reverse that
	task.wait(1) -- wait for the reverse tween to finish
end)
--//

and you should have something like this
Showcase

and thats it, you have just successfully replicated an effect to all the clients Good Job!

Replicating a move to client.

Ah you picked the hard choice, brave scripter. I have this effect. Fireball - Roblox that looks like this
image
so in our server script we are going to add the following, a hitbox and hit detection and values to send to the clients.

local rem = script.Parent
local ts = game:GetService("TweenService")
rem.OnServerEvent:Connect(function(plr) -- when you recieve the remote with the player that fired it
	local char = plr.Character 
	local hrp = char:WaitForChild("HumanoidRootPart")
	local positiontospawntheeffect = hrp.CFrame * CFrame.new(0, 0, -5) -- position the effect in the same position as the hrp
	local CFRametween = {CFrame = hrp.CFrame * CFrame.new(0, 0, -500)} -- the end goal position
	rem:FireAllClients(positiontospawntheeffect, CFRametween) -- we send the position to all the clients
	
	local hitbox = Instance.new("Part") -- create a part
	hitbox.CFrame = positiontospawntheeffect -- put it in the same pos as the effect
	hitbox.Parent = workspace -- parent it to the workspace
	game:GetService("Debris"):AddItem(hitbox, 5) -- add it for 5 secs
	hitbox.Transparency = 1 -- make it invisible
	hitbox.Size = Vector3.new(5,5,5) -- make it a size of ur choice
	hitbox.CanCollide = false -- make it so that it can not collide with anything
	hitbox.Anchored = true -- anchor it 
	ts:Create( -- create a tween for it exactly like the vfx tween
		hitbox,
		TweenInfo.new(4,
			Enum.EasingStyle.Quad,
			Enum.EasingDirection.InOut
		),
		CFRametween
	):Play()
	
	-- really basic damage detection function
	local gotHit = false
	hitbox.Touched:Connect(function(hit)
		if hit.Parent:FindFirstChild("Humanoid") and hit.Parent ~= char and gotHit == false then
			gotHit = true
			hit.Parent:FindFirstChild("Humanoid"):TakeDamage(5)
		end
	end)
end)

then in our local script we are going to add a similar script to the other one in the “Just Replicating to client” version

--// shortcuts
local rs = game:GetService("ReplicatedStorage")
local ts = game:GetService("TweenService")
local ti = TweenInfo.new(4, Enum.EasingStyle.Quad, Enum.EasingDirection.InOut)
--//

--// replication function
rem.OnClientEvent:Connect(function(Cframe, endGoal)
	local effect = rs:WaitForChild("FireballEffect"):Clone() -- clone ur effect 
	effect.Anchored = true -- anchor the effect cant move
	effect.CanCollide = false -- can collide off so you cant collide with the object
	effect.CFrame = Cframe -- the position identified in the server script
	effect.Parent = workspace -- parent the effect to workspace
	game:GetService("Debris"):AddItem(effect, 7) -- add the item for 7 secs
	ts:Create(effect, ti, endGoal):Play() -- play the tween from the info specified in the server script
	task.wait(4) -- wait a bit
	ts:Create(effect, TweenInfo.new(1), {Transparency = 1}):Play() -- reverse that
	task.wait(1) -- wait for the reverse tween to finish
end)
--//

and you should have a working client replicated fireball that does damage! Good job!

BEFORE YOU LEAVE, ONLY REPLICATE VFX NOT HITBOXES OR ITLL BE VULNERABLE TO EXPLOITERS

To sum it up, client replication is when one player sends a remote to the server, and the server returns similar values to all the clients “replicating” it.

Thanks for coming here, and reading all the way through, i hope you learned how to replicate effects to the client, this is my first tutorial post on here, so let me know if i can add anything to improve or if you need any help! Thanks and goodbye! :sunglasses:

18 Likes

Great tutorial! I think it will really help developers who want to learn more about this topic. One issue I have found is that this topic should be posted in #resources:community-tutorials. This is not a question related to scripting (Its not a question at all) and hence, does not belong in this category. Other that that, I dont think there are no issues!

2 Likes

oo alrighty thanks for letting me know!

Y’know you cant just detect hitboxes on the server as the server itself does not know if the player is hitting the hitbox as the client isnt tellin the server that the object is here right? My current solution is to both tween it in server and client, but that wouldnt be smooth as expected as if the client is lagging, the server and client would fight each other. Any solutions on how to make a smooth tween yet unexploitable hitboxes?

i believe that tweening the Hitbox and effect with the same properties would detect this. I have had great accuracy doing this. As when the effect is used, the server tweens the hitbox and the effect with the same end goal with a max off 0.2 sec difference. Im sorry if that doesnt help, didnt fully understand your question and your problem

tweening the hitbox in server? Then that would kinda ruin the purpose of “i will not get hurt” and smooth tween

if you tween the hitbox in the client, it would be viable to exploit attacks, changing the range etc

I don’t understand how you get accurate hitboxes on the server… Have you tried creating a projectile on the server? It can be delayed on the client’s view but can look perfectly accurate on the server. Yes handling hitboxes on the client will make it easily exploitable, but you could probably solve the issue with some security checks. IMO creating hitboxes on the client is the best way to handle hitboxes. I couldn’t release a game with such inaccurate hitboxes. For example, a projectile that explodes way before it actually hits something.

Yeah, for sure, You could easily do something like that with updating a value on detection from the client. But that goes more into depth for beginners, doing it on the server is just easeir for explanation and teaching sake.

It is redundant for the client to fire the server and then the server to fire the same client back. Instead, the client that initiates the action can have the VFX effects played when they initiate the action, and then the server fires the other clients to replicate those effects. This also creates a smoother experience.

Tweening definitely shouldn’t be used for projectiles. I’d definitely recommend looking into FastCast for projectiles as it has saved me a lot of time over the past few years.