Roblox Architecture de Combat : Hitbox, Compensation de Lag et Tampons Rollback

Combat responsiveness is the defining metric for action RPGs, battlegrounds, and sword fighting games on Roblox. If swings pass cleanly through opponents or register two seconds after the blade swings, competitive integrity dissolves.

By implementing server-side position history buffers, ping-compensated raycasting, spatial hash indexing, and heuristic anti-exploit velocity validation, developers can create razor-sharp melee and projectile combat that feels instantaneous on client viewports while remaining 100% exploit-proof.

1. The Client-Server Hit Detection Dilemma

Balancing player feedback latency against server security:

• The Exploiter Vulnerability of Client Trust: Never let clients fire DamageRemote:FireServer(targetHumanoid, 50). Malicious executors can wipe entire servers instantly.
• The Lag Penalty of Pure Server Detection: If the server tests hitboxes in present time, high-ping players miss targets they clearly sliced on their local screens due to round-trip transit delay.
• Client-Prediction / Server-Validation Paradigm: The client plays visual FX instantly and sends a timestamped swing intent; the server rewinds time to verify if the attack was physically possible.

2. Temporal Position Rollback Buffers (History Ring Buffers)

Tracking historical player positions to evaluate attacks in the past:

• Circular Ring Buffer: Maintain an array of recent position snapshots for every character over the last 1.0 second (sampled at 30Hz or 60Hz).
• Timestamp Interpolation: When validating an attack at time T = ServerTime - (PlayerPing / 2), lerp between the two closest recorded history snapshots.
• Maximum Rewind Clamping: Cap the rewind limit strictly to 200ms to prevent extreme high-ping players from hitting opponents who have long since dashed behind cover.

-- Server-Side Temporal Rollback Hitbox Validator
local RollbackValidator = {}
RollbackValidator.__index = RollbackValidator

local MAX_REWIND_SECONDS = 0.20 -- Maximum 200ms ping compensation
local BUFFER_CAPACITY = 60

function RollbackValidator.new()
    local self = setmetatable({}, RollbackValidator)
    self.History = {} -- [player] = { {Time = t, Pos = Vector3} }
    return self
end

function RollbackValidator:RecordPosition(player, currentPos, serverTime)
    local buffer = self.History[player]
    if not buffer then
        buffer = {}
        self.History[player] = buffer
    end
    table.insert(buffer, {Time = serverTime, Pos = currentPos})
    if #buffer > BUFFER_CAPACITY then
        table.remove(buffer, 1)
    end
end

function RollbackValidator:GetHistoricalPosition(player, targetTime)
    local buffer = self.History[player]
    if not buffer or #buffer == 0 then return nil end

    -- Clamp to maximum rewind threshold
    local clampedTime = math.max(targetTime, os.clock() - MAX_REWIND_SECONDS)
    
    for i = #buffer, 2, -1 do
        local pCurrent = buffer[i]
        local pPrev = buffer[i - 1]
        if pCurrent.Time >= clampedTime and pPrev.Time <= clampedTime then
            local alpha = (clampedTime - pPrev.Time) / (pCurrent.Time - pPrev.Time)
            return pPrev.Pos:Lerp(pCurrent.Pos, math.clamp(alpha, 0, 1))
        end
    end
    return buffer[1].Pos
end

return RollbackValidator

3. Spatial Hash Grids for High-Density Proximity Queries

Optimizing spatial entity lookups without iterating over all server players:

• 2D/3D Spatial Bucketing: Partition the map into 16x16 stud buckets; entities register their current bucket index upon moving.
• O(1) Proximity Filtering: During an attack, only query characters situated in neighboring buckets rather than looping through all 100 players in the server.
• Garbage Collection & Memory Footprint: Use numerical hash keys (e.g., chunkX * 73856093 ^ chunkZ * 83492791) to keep bucket lookups ultra-fast in Luau.

4. Geometric Hitbox Verification & Raycast Sweeps

Constructing physically accurate, non-laggy weapon swing volumes:

• Shaft Raycast Sweeps: Attach multiple attachments along the weapon blade and cast rays between consecutive frames to form an unbroken cutting polygon.
• Rotated Bounding Box (OBB) Checks: Test if target limb positions fall inside the weapon swing arc CFrame volume during the validated historical frame.
• Line-of-Sight (LoS) Raycasting: Verify that no walls or solid obstacles obstructed the space between the attacker and victim at the moment of impact.

5. Heuristic Anti-Exploit Filters: Velocity & Teleport Clamping

Neutralizing client-side speed hacks, noclip, and reach modifiers:

• Maximum Reach Clamping: Reject any hit where the distance between attacker and target exceeds weapon length plus latency movement tolerance.
• Delta Velocity Verification: Verify that the attacker was physically capable of reaching the attack origin without exceeding maximum Humanoid WalkSpeed.
• Attack Rate Limiting: Enforce strict cooldown state machines per weapon archetype to discard rapid-fire macro injection attacks.

Frequently Asked Questions