Roblox Custom Character Movement: Wall Running, Ledge Grabs & VectorForce Physics

Fast-paced movement mechanics like wall running, sliding, and ledge mantling define modern competitive action games. Attempting to build fluid parkour using default Humanoid state changes often results in sticky collision glitches, erratic momentum loss, and frustrating falls.

By leveraging modern Luau physics constraints—specifically `LinearVelocity`, `VectorForce`, and directional raycasting—developers can construct responsive, server-authoritative custom movement controllers that deliver AAA platforming feel across PC, console, and mobile.

1. Overriding Default Humanoid States for Fluid Parkour

Foundations of custom movement state machines in Roblox Studio:

• Disabling Conflicting Humanoid States: When wall running initiates, immediately invoke Humanoid:SetStateEnabled(Enum.HumanoidStateType.Climbing, false) and disable Freefall to prevent the default falling animation from overriding procedural physics.
• RootPart Network Ownership: Ensure the client maintains explicit network ownership of their character's HumanoidRootPart via rootPart:SetNetworkOwner(player) to eliminate input-to-physics latency.
• State Machine Modularity: Architecture movement using a finite state machine (Walking, Sprinting, WallRunning, LedgeHanging, Vaulting) with distinct entry, tick, and exit hooks.

2. Directional Raycasting & Surface Normal Alignment

Detecting runnable geometry and calculating traversal vectors:

• Multi-Raycast Probes: Cast horizontal raycasts from the character's hip and shoulder positions to the left and right (typically 2.5–3.5 studs) to detect vertical wall surfaces.
• Surface Normal Evaluation: Extract the hit surface normal vector. Ensure the surface angle is perpendicular (within 75° to 105° relative to the world up vector) to prevent running on shallow ramps.
• Forward Vector Projection: Calculate the wall-run direction using the cross product: wallNormal:Cross(Vector3.yAxis), orienting traversal parallel to the wall contour.

3. Modern Physics Constraints: LinearVelocity & VectorForce

Replacing deprecated BodyMovers with constraint-based forces:

• LinearVelocity for Constant Speed: Attach a LinearVelocity constraint to HumanoidRootPart. Set VelocityConstraintMode to Vector and configure MaxForce high enough to counteract lateral friction while maintaining a constant forward pace.
• VectorForce for Anti-Gravity: Counteract the workspace gravity acceleration (typically 196.2 studs/s²) with an upward VectorForce calculated as characterMass * workspace.Gravity * antiGravityFactor.
• Controlled Vertical Drift: Gradually decay the upward force over 1.5–2.5 seconds to create a realistic downward arc, establishing a skill-based time limit on continuous wall runs.

-- Modern Wall Running Physics Controller (Client-Side)
local RunService = game:GetService("RunService")
local WallRun = {}
WallRun.__index = WallRun

function WallRun.new(character)
    local self = setmetatable({}, WallRun)
    self.Char = character
    self.RootPart = character:WaitForChild("HumanoidRootPart")
    self.Humanoid = character:WaitForChild("Humanoid")
    
    -- Setup LinearVelocity Constraint
    local att = Instance.new("Attachment", self.RootPart)
    local lv = Instance.new("LinearVelocity")
    lv.Attachment0 = att
    lv.MaxForce = 15000
    lv.RelativeTo = Enum.ActuatorRelativeTo.World
    lv.Enabled = false
    lv.Parent = self.RootPart
    
    self.Attachment = att
    self.LinearVelocity = lv
    self.IsRunning = false
    return self
end

function WallRun:CheckWall(side)
    local rayDir = (side == "Left" and -self.RootPart.CFrame.RightVector or self.RootPart.CFrame.RightVector) * 3.5
    local params = RaycastParams.new()
    params.FilterDescendantsInstances = {self.Char}
    params.FilterType = Enum.RaycastFilterType.Exclude
    
    return workspace:Raycast(self.RootPart.Position, rayDir, params)
end

function WallRun:Start(hitNormal, forwardDir)
    self.IsRunning = true
    self.LinearVelocity.VectorVelocity = forwardDir * 32 + Vector3.new(0, 4, 0)
    self.LinearVelocity.Enabled = true
    self.Humanoid:ChangeState(Enum.HumanoidStateType.Physics)
end

function WallRun:Stop()
    self.IsRunning = false
    self.LinearVelocity.Enabled = false
    self.Humanoid:ChangeState(Enum.HumanoidStateType.Freefall)
end

return WallRun

4. Procedural Ledge Grabbing & Mantle Transitions

Detecting ledges and executing seamless climb-up animations:

• Two-Tier Ledge Detection: Cast a chest-height ray forward to confirm wall contact, combined with a downward ray cast from above the wall to find the exact ledge top edge.
• RootPart Snapping: Anchor or clamp character position using an AlignPosition constraint when the ledge is grabbed, allowing the player to hang or shimmy.
• Tweened Mantle Curve: When the jump key is pressed while hanging, play a climb animation while smoothly interpolating the RootPart position up and over the ledge edge using a quadratic bezier curve.

5. Mobile Touch Controls & Server Validation

Ensuring accessibility across devices while preventing teleport exploits:

• ContextActionService Touch Binding: Bind wall-jump and mantle inputs to dynamic on-screen action buttons with generous touch hitboxes (minimum 48x48 pixels).
• Server-Side Speed Clamping: The server must calculate velocity deltas between replication ticks. Allow higher velocity thresholds exclusively during verified wall-run states.
• Sanity Raycasts on Server: Re-verify that a valid wall existed near the player's position during the reported wall-run window before confirming client positions.

Frequently Asked Questions