Simulation

In this section we will explore setting up a basic simulation along side the different things we must account for in order to create a working simulation.

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Setting up your workspace

SecureCast requires a Map and Characters folder placed within workspace to function correctly.
All parts of the map must be a descendant of the Map folder.
All player characters must be paranted to the Characters folder.

We will also need an Events folder within ReplicatedStorage. Add a RemoteEvent named Simulation under the Events folder.

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Setting up your client

Create a LocalScript and place it under StarterPlayerScripts. Copy and paste the following code into the script you just created:

--!strict

local Players = game:GetService("Players")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local UserInputService = game:GetService("UserInputService")

local SecureCast = require(ReplicatedStorage.SecureCast)

local Player = Players.LocalPlayer
local Mouse = Player:GetMouse()

local Events = ReplicatedStorage.Events
local SimulateEvent = Events.Simulate

--> Only call once per context
SecureCast.Initialize()

UserInputService.InputBegan:Connect(function(Input, GPE)
    if GPE or Input.UserInputType ~= Enum.UserInputType.MouseButton1 then
        return
    end

    local Character = Player.Character
    local Head = Character and Character:FindFirstChild("Head")
    if not Head then
        return
    end

    local Origin = Head.Position
    local Direction = (Mouse.Hit.Position - Origin).Unit

    --> Replicate to the server
    SimulateEvent:FireServer(Origin, Direction, workspace:GetServerTimeNow())

    --> Cast the projectile within our own simulation
    SecureCast.Cast(Player, "Bullet", Origin, Direction, os.clock())
end)

SimulateEvent.OnClientEvent:Connect(function(Caster: Player, Type: string, Origin: Vector3, Direction: Vector3, PVInstance: PVInstance?, Modifer)
    if Caster ~= Player then
        SecureCast.Cast(Caster, Type, Origin, Direction, os.clock(), PVInstance, Modifer)
    end
end)

Setting up your server

Create a Script and place it under ServerScriptService. Copy and paste the following code into the script you just created:

--!strict

local Players = game:GetService("Players")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RunService = game:GetService("RunService")

local SecureCast = require(ReplicatedStorage.SecureCast)

local MAXIMUM_LATENCY = 0.8 -- 800 ms

local Events = ReplicatedStorage.Events
local SimulateEvent = Events.Simulate

--> Only call once per context
SecureCast.Initialize()

Players.PlayerAdded:Connect(function(Player: Player)
    --> We must parent all characters to the Characters folder within workspace
    Player.CharacterAdded:Connect(function(Character)
        RunService.PostSimulation:Wait()
        Character.Parent = workspace.Characters
    end)

    --> Disable raycast interactions with accessories
    Player.CharacterAppearanceLoaded:Connect(function(Character)
        for _, Child in Character:GetChildren() do
            if not Child:IsA("Accessory") then
                continue
            end

            local Handle: BasePart? = Child:FindFirstChild("Handle") :: BasePart
            if Handle then
                Handle.CanQuery = false
            end
        end
    end)
end)

ReplicatedStorage.Events.Simulate.OnServerEvent:Connect(function(Player: Player, Origin: Vector3, Direction: Vector3, Timestamp: number)
    --> It is best to have calculate these values at the top
    --> We can have the most accurate latency values this way
    --> Calculating them further down may result in skewed results

    --> We must take into account character interpolation
    --> The best estimate for this value available is (PLAYER_PING + 48 ms)
    --> If we do not factor in interpolation we will end up with inaccurate lag compensation

    local Time = os.clock()
    local Latency = (workspace:GetServerTimeNow() - Timestamp)
    local Interpolation = (Player:GetNetworkPing() + SecureCast.Settings.Interpolation)

    --> Validate the latency and avoid players with very slow connections
    if (Latency < 0) or (Latency > MAXIMUM_LATENCY) then
        return
    end

    --> Validate the projectile origin
    local Character = Player.Character
    local Head: BasePart? = Character and Character:FindFirstChild("Head") :: BasePart
    if not Head then
        return
    end

    local Distance = (Origin - Head.Position).Magnitude
    if Distance > 5 then
        warn(`{Player} is too far from the projectile origin.`)
        return
    end

    --> Replicate the projectile to all other clients
    SimulateEvent:FireAllClients(Player, "Bullet", Origin, Direction)

    --> Cast the projectile within our own simulation
    SecureCast.Cast(Player, "Bullet", Origin, Direction, Time - Latency - Interpolation)
end)

Test your simulation

You can test if your simulation is working properly by going into a Local Test Server.

Note

Make sure to create 2 seperate teams or the players will be ignored due to being on the same team.