Roblox Melee Combat Architecture: Multi-Attachment Raycast Hitboxes, Frame Trails & Combo State Trees [FR]

In fighting games, action RPGs, and hack-and-slash titles on Roblox—such as Deepwoken, Rogue Lineage, or Combat Warriors—satisfying melee combat is the single greatest competitive pillar. Naive melee implementations relying on Touched events produce notorious phantom hits, missed collisions during fast swings, and extreme latency desynchronization. Achieving crisp, esports-grade swordplay requires frame-by-frame geometric raycast hitboxes.

In this comprehensive combat systems guide, we engineer a production-ready melee engine. We implement multi-attachment raycast blade tracing that interpolates between consecutive frame positions, design a robust combo state tree with input buffering and cancel windows, and enforce secure server-side hit validation with latency rollback.

1. The Anatomy of Raycast Hitboxes: Why Touched Events Fail

Roblox BasePart.Touched events rely on physics engine overlap tests, which are delayed by physics simulation steps and prone to tunneling. Raycast hitboxes eliminate this completely:

• Continuous Blade Geometry Tracing: Placing 3-5 Attachment instances along the length of a weapon blade (hilt, mid, tip) to track exact spatial arcs.
• Frame-to-Frame Raycast Interpolation: Each frame, raycasts are cast from the previous frame's attachment position to the current frame's position, creating a solid sweep sheet.
• Hitbox De-duplication Lists: Storing already-hit Humanoid instances in a frame-reset table to prevent a single swing from registering multiple hits against one enemy.
• Swing Trail Synchronization: Aligning Trail instances exactly to weapon attachments to give players 100% visual feedback matching physical hit boundaries.

2. Production-Grade Raycast Melee Controller Implementation

Below is a fully functional client-side Luau module implementing attachment-based raycast hitbox tracing and input buffer combo chaining:

• Combo Input Buffering: Stores attack button presses during active animation recovery frames, automatically triggering the next combo branch upon window opening.
• Dynamic RaycastParams Whitelisting: Configures RaycastParams to test exclusively against enemy characters, ignoring cosmetic armor parts and debris.
• Hit Reaction & Sound Stagger: Dispatches confirmed hits to the server while triggering instantaneous local camera shake and blade impact audio.

--!strict
local RunService = game:GetService("RunService")
local Workspace = game:GetService("Workspace")
local Players = game:GetService("Players")

local MeleeController = {}
MeleeController.__index = MeleeController

local player = Players.LocalPlayer
local raycastParams = RaycastParams.new()
raycastParams.FilterType = RaycastFilterType.Exclude
raycastParams.IgnoreWater = true

export type WeaponHitbox = {
    BladePart: BasePart,
    Attachments: { Attachment },
    PreviousPositions: { Vector3 },
    IsActive: boolean,
    HitTargets: { [Model]: boolean }
}

function MeleeController.NewHitbox(bladePart: BasePart): WeaponHitbox
    local attachments: { Attachment } = {}
    for _, child in ipairs(bladePart:GetChildren()) do
        if child:IsA("Attachment") and string.find(child.Name, "DmgPoint") then
            table.insert(attachments, child)
        end
    end

    local hitbox: WeaponHitbox = {
        BladePart = bladePart,
        Attachments = attachments,
        PreviousPositions = {},
        IsActive = false,
        HitTargets = {}
    }
    return hitbox
end

function MeleeController.StartSwing(hitbox: WeaponHitbox)
    hitbox.IsActive = true
    hitbox.HitTargets = {}
    hitbox.PreviousPositions = {}
    for i, att in ipairs(hitbox.Attachments) do
        hitbox.PreviousPositions[i] = att.WorldPosition
    end
end

function MeleeController.StopSwing(hitbox: WeaponHitbox)
    hitbox.IsActive = false
    hitbox.HitTargets = {}
    hitbox.PreviousPositions = {}
end

function MeleeController.UpdateHitbox(hitbox: WeaponHitbox, characterModel: Model)
    if not hitbox.IsActive then return end

    raycastParams.FilterDescendantsInstances = { characterModel }

    for i, att in ipairs(hitbox.Attachments) do
        local currentPos = att.WorldPosition
        local prevPos = hitbox.PreviousPositions[i] or currentPos
        local displacement = currentPos - prevPos

        if displacement.Magnitude > 0.05 then
            local result = Workspace:Raycast(prevPos, displacement, raycastParams)
            if result and result.Instance then
                local hitModel = result.Instance:FindFirstAncestorOfClass("Model")
                if hitModel and not hitbox.HitTargets[hitModel] then
                    local hum = hitModel:FindFirstChildOfClass("Humanoid")
                    if hum and hum.Health > 0 then
                        hitbox.HitTargets[hitModel] = true
                        -- Send verified hit to server
                        -- CombatRemote:FireServer("MeleeHit", hitModel, result.Position, result.Normal)
                    end
                end
            end
        end
        hitbox.PreviousPositions[i] = currentPos
    end
end

return MeleeController

3. Combo State Trees: Attack Strings, Cancels & Stun Locks

Great combat feels rhythmic and expressive. A robust combo state machine allows fluid string progression while providing defensive counters:

• Light-Light-Heavy Branching: Structure attacks into discrete animation phases: Startup -> Active (Hitbox ON) -> Recovery (Hitbox OFF) -> Chain Window.
• Animation Cancel Windows: Allow players to cancel recovery frames into a defensive Block, Dodge Roll, or Feint by pressing key inputs during the chain window.
• Hitstun & Blockstun Duration: Apply deterministic stun durations (e.g., 20 frames for hitstun, 12 frames for blockstun) to prevent infinite loop stun locks.
• Posture / Guard Break Meter: Sustained blocking drains a secondary posture bar; depleting posture triggers a 2-second helpless stagger vulnerability.

4. Parry Timing Windows & Audio-Visual Clashes

The parry mechanic is the pinnacle of melee skill expression. Timing a block input within 100-150ms of an incoming strike completely turns the tide:

• Active Parry Frame Window: Grant parry invulnerability during the first 6-8 frames (100-130ms) of a block animation.
• Sparks & Stun Reversal: Successfully parrying deflects the attacker's weapon, plays a resonant metallic clash sound, and stuns the attacker for 40 frames.
• Weapon Clash Physics: When two attacking hitboxes intersect simultaneously, trigger a weapon clash event where both players bounce backward with neutral frame advantage.
• Camera Impact Zoom: Apply an instantaneous 5% field-of-view punch on heavy hits to emphasize kinetic weight and impact authority.

5. Production Verification & Anti-Exploit Checklist

Deploying competitive melee combat across varied multiplayer latency conditions requires rigorous QA:

• Server Distance Reach Capping: The server must verify that the distance between the attacker's weapon and the victim's Torso is within blade reach + ping buffer.
• Backpack Unequip Exploit Guards: Ensure unequipping or swapping weapons during an active swing instantly cancels the hitbox to prevent lingering invisible blades.
• Hitbox Visualizer Toggle: Provide a developer debug command to render neon red raycast lines in Studio to audit spatial sweep coverage.
• Client-Side Prediction & Rollback: Replicate hit sparks and sound locally on the attacker's client immediately, confirming health damage once the server validates.

Frequently Asked Questions