Runtime Advanced Cables

A physics cable and rope toolkit for Unreal Engine. Verlet simulation, surface draping, player interaction, tethering, riding, swinging, climbing, and towing - all from Blueprint.

Quick Start Guide →

RAC ships two cable actors, each built on a different solver. Pick the one that fits your use case - most components (cutting, tether, swing, climb, tow, interaction) work with both.

Cable Actor

RAC Cable

Verlet physics with spline mesh visuals. The general-purpose cable with beam effects, runtime pinning, and cable networks.

Build with it

• Power lines & wiring
• Beams & lasers
• Grappling hooks & ziplines
• Tow cables & tripwires
• Vine & tendril VFX
• Leashes & tethers

Wrapping Cable

RAC Wrapping Cable

Section-based solver that dynamically wraps around world geometry. Shares most features with Cable Actor plus geometry conformance.

Build with it

• Rope around corners
• Winch & pulley puzzles
• Climbing & rappelling
• Drag & pull-back
• Cable routing
• Cuttable terrain ropes

Feature Support

Feature / Component	Cable Actor	Wrapping Cable
Cable Cutting	Yes	Yes
Runtime Pinning	Yes	No (wrap anchors)
Extend / Retract	Yes	Yes
LOD Tiers	Yes (4-tier)	Yes (4-tier)
World Collision	Yes	Yes
Cable Interaction (grab)	Yes	Yes
Cable Interaction (cut)	Yes	Yes
Cable Interaction (pin)	Yes	No
Tether Component	Yes	Yes
Cable Point	Yes	No
Pulley	Yes	No
Zipline	Yes	Yes
Climbing	Yes	Yes
Swing	N/A	N/A
Tether Utils	Yes	No
Web Utils	Yes	No
Geometry Wrapping	No	Yes
Wrap Anchors	No	Yes
Cable Debug	Yes	Yes

Components & Features

Installation

1. Purchase/download RAC from Fab
2. In UE, go to Edit > Plugins, search for RAC, enable it
3. Restart the editor
4. All components are now available in the Add Component menu and Blueprint palette

Placing Cables

There are several ways to get cables into your level. Pick whichever fits your workflow:

All methods produce the same Cable Actor or Wrapping Cable - they just differ in when and how the cable is created. You can mix and match freely.

Cable Cutting

Both cable types - Cable Actors and Wrapping Cables can both be cut at runtime.

Cut any cable at any point at runtime. The original cable keeps the head portion, and a new cable of the same type spawns for the tail with its own physics, visuals, and events. Both halves continue simulating independently with free-falling cut ends.

How It Works

1. The Verlet solver truncates the original cable's particles to [0..CutIndex] and sets bFreeEnd = true so the cut end falls naturally
2. A new Cable Actor is spawned with the remaining particles [CutIndex..End], inheriting all visual settings (mesh, material, scale, end caps, flow tiling)
3. Existing pins are remapped. Pins on the head stay on the original, pins on the tail transfer to the new cable with corrected indices
4. OnCableCut fires on both the Verlet component and the Cable actor with references to both halves

Setup

1. On your Cable actor, select the VerletCable child component and set bAllowCutting = true
2. Optionally set MinCutParticles on the Cable actor (default 3). Prevents tiny unusable scraps
3. Optionally enable bAutoDestroyCutPieces to clean up cut-off pieces after AutoDestroyDelay seconds
4. Optionally enable bRegrowAfterCut to have the cable grow back to its original length

Ways to Cut

Events

Auto-Cleanup & Regrow

• Auto-destroy: Enable bAutoDestroyCutPieces on the Cable Actor to automatically clean up cut-off pieces after AutoDestroyDelay seconds (default 5). Set bOnlyDestroyUnattached = true (default) to keep pieces that are still connected to something.
• Regrow: Enable bRegrowAfterCut to make the cable grow back to its original length after being cut. The free end extends outward at RegrowSpeed (default 200 u/s) after RegrowDelay seconds (default 1.0). OnCableRegrown fires when complete.

Example Uses

• Sword slash: Bind StartSweepCut/StopSweepCut to your melee attack. Swing through a room full of cables and slice them all in one motion
• Power lines: Cut cables to disable circuits. Bind OnCableCut to toggle bCableActive on both halves and trigger downstream logic
• Trap wires: Projectile line trace + CutCableAtWorldPosition = shoot to sever tripwires
• Grapple ropes: Player cuts their own tether mid-swing for a momentum launch
• Puzzle cables: Cut and reconnect cable networks to reroute energy paths
• Destruction: Combine with physics coupling. Cut a cable holding a physics object and watch it fall
• Regenerating vines: Enable bRegrowAfterCut for cables that grow back after being severed

Performance Tips

Quick reference for keeping cable counts high and frame times low. Each class section below has full details on these properties.

• Use Cable Point defaults. They're already tuned for ambient cables (6 solver iterations, 1 substep, auto-sleep)
• Enable LOD Tiers. Enabled by default on Cable Points. Distant cables drop to fewer iterations and lower visual updates
• Global Cable Budget: SetCableBudget(MaxFull, MaxMedium) caps how many cables run at Full/Medium LOD (default 8 Full, 16 Medium)
• Settle Time: Cables sleep after settling. Default 2s via Cable Point defaults (CableSettleTime), 0 on standalone VerletCable. Sleeping cables skip simulation entirely.
• Collision Round-Robin: MaxTracesPerFrame (default 8) spreads collision traces over multiple frames
• MaxVisualSegments: Cap spline mesh count for far cables. LOD tiers auto-reduce visual segments.
• MaxAutoSubsteps: Caps auto-substep scaling at low FPS to prevent death spiral (default 2 on Cable Points)
• LOD visual hiding: Cables at Low and Sleeping LOD tiers automatically hide their spline meshes, saving GPU draw calls. Toggle bHideVisualsAtLow and bHideVisualsAtSleep per cable. Enabled by default.
• LOD shadow disable: Shadow casting is automatically disabled at Low and Sleeping LOD tiers to save shadow map draw calls. Shadows restore at Medium/Full. Toggle bDisableShadowsAtLowLOD per cable. Enabled by default.

Editor Visualizer

When you select a cable actor (Cable Actor or Wrapping Cable) in the viewport, the editor draws an overlay showing cable state. No configuration needed - it activates on selection.

Cable Placement Tool

An interactive editor mode for placing cables directly in the viewport. Activate it from the Modes dropdown (or the Modes toolbar) - look for RAC Cable Placement. The mode provides four tools in its toolbar: Route, Delete, Select, and Wrap.

Route Tool

The main placement tool. Left-click in the viewport to set a start point, then left-click again to place a cable between the two points. The tool chains automatically - after placing a cable, the end point becomes the next start point so you can keep clicking to lay out a cable run.

While hovering between clicks, a catenary preview line shows where the cable will hang. The preview updates in real time as you move the mouse and adjust slack.

Snapping

When bSnapToExisting is enabled (default), the cursor snaps to nearby cable endpoints and Cable Point components within the snap radius. This makes it easy to connect cables to existing attachment points or chain off other cables.

Delete Tool

Hover over a cable to highlight it, then left-click to delete it. Works on both Cable Actors and Wrapping Cables.

Select Tool

Two modes of selection depending on where you click:

• Click a Cable Actor - selects that cable and all cables connected to it (follows the chain through shared endpoint actors via BFS). Great for selecting an entire cable run or network for bulk property edits.
• Click a Wrapping Cable - selects that individual cable (wrapping cables are standalone, no chain selection).
• Click empty space - selects every Cable Actor and Wrapping Cable in the level.

Placement Settings

When the Route tool is active, a settings panel appears in the mode's Details panel. These settings apply to all cables placed while they are set.

Wrapping Cable Placement

The Wrap tool in the Cable Placement mode lets you route Wrapping Cables around geometry by clicking surfaces. Each click adds a wrap anchor point, and the cable is spawned pinned to those points at runtime.

Workflow

Select the Wrap tool from the Cable Placement mode toolbar. Then click surfaces in the viewport to build a cable route.

Preview

While routing, committed segments between placed points show in dark blue and the live segment from the last point to the cursor shows in cyan. Each segment displays a catenary curve based on the current slack ratio, so you can see the approximate sag before finishing.

How Anchors Work

Each anchor you place is offset slightly from the surface (by WrapCollisionRadius) and pinned permanently at runtime. These manual anchors are never removed by the auto-unwrap system - the cable stays routed through your clicked points. The runtime wrapping system can still add and remove its own dynamic anchors between your manual ones.

If the cable is attached to an actor at the start point (i.e. you clicked on a movable actor), the cable's start will follow that actor at runtime.

Placement Settings

When the Wrap tool is active, a settings panel appears in the mode's Details panel. These settings apply to the next cable you place.

Segments & Tiling

Every RAC cable has two independent segment counts - one for physics, one for visuals. Understanding the difference is key to getting cables that look great without wasting performance.

Simulation Segments (CPU)

NumSegments controls how many particles the Verlet solver simulates. More particles means smoother curves and more accurate physics, but each particle adds CPU cost every frame. A heavy rope bridge might need 40-60 segments for realistic sag, while a short electrical wire can get away with 4-6.

Visual Segments (GPU)

MaxVisualSegments controls how many spline mesh pieces are used to render the cable. This is completely independent of the simulation - you can simulate 50 particles but only render 12 mesh segments. The visual system interpolates between particles to produce a smooth curve regardless.

Each LOD tier can further reduce the visual count:

• Full LOD: Uses MaxVisualSegments (default 64, or NumSegments if set to 0)
• Medium LOD: Auto halves the Full count (or set LODMediumVisualSegments manually)
• Low LOD: Auto quarters the Full count, minimum 4 (or set LODLowVisualSegments manually)

Flow Tiling (UV)

FlowTiling controls how many times the material texture repeats along the cable length. At 1.0 (default), the texture stretches once across the whole cable. At 4.0, it tiles four times. This works because RAC creates a separate Dynamic Material Instance for each visual segment and sets continuous UVOffset / UVScale values so the texture flows seamlessly across all segments.

Practical Guidelines

Flow Materials

RAC automatically creates Dynamic Material Instances per segment with continuous UV flow. To use this in your materials:

1. Add two ScalarParameter nodes named UVOffset (default 0) and UVScale (default 1)
2. Apply them to your V coordinate: adjustedV = meshV * UVScale + UVOffset
3. Use FlowTiling / VisualFlowTiling / LinkFlowTiling to control how many times the texture repeats along the cable

Wind & Drift

Two systems give cables organic ambient motion without any Blueprint logic. Both are per-cable settings on the Verlet Cable Component (or inherited via Cable Point defaults). Wrapping Cables have their own matching Drift and Wind properties with the same behavior.

World Wind

Drop a Wind Directional Source actor into the level and enable bUseWorldWind on any cable. The cable samples the scene wind each frame and pushes particles accordingly. Per-particle Perlin noise (WindTurbulence) adds flutter so the cable ripples instead of just leaning.

Ambient Drift

Small Perlin-based forces that give cables gentle ambient movement - perfect for underwater, sci-fi, or organic environments. No Wind Source needed; drift is self-contained per cable.

Cable Actor RAC Cable

The cable actor. Verlet physics with spline mesh visuals, overlap capsules, end caps, pin indicator meshes, and gameplay active/inactive state.

Functions

Extend / Retract Functions

Active State Functions

Active State Events

Cutting

Wrapping Cable RAC Wrapping Cable

A standalone cable actor that dynamically wraps around world geometry under tension. Uses section-based simulation: wrap anchors pin the cable to surfaces, with independent verlet chains between them for natural sag. Tight sections stay straight, slack sections drape with gravity.

Properties

Functions

Events

Rideable Cable / Zipline RAC Zipline Cable

Works with both - Cable Actors and Wrapping Cables both support zipline riding.

Ride along cables using Zipline Cable - a Cable Actor subclass with ride physics built in. Place it in your level, call StartRiding(Character), and the player rides along the cable polyline. Auto-direction, gravity-influenced speed, deceleration at ends, pendulum swing mode. Tick disabled until ride starts.

Functions

Events

Tether Point RAC Tether Point

A placeable tether anchor point. Drop into your level to create attachment locations for the Tether Component. Connect via TetherToActor(TetherPoint). Optional mesh visual and detection sphere for overlap-based discovery.

Tether Component RAC Tether

Visible rope to any target. Add to your character and call TetherToCable, TetherToWrappingCable, TetherToActor, or TetherToPoint to connect. Creates a visual link cable between the player and the attachment point. Supports pull-back mode, leash physics, connect/disconnect animations.

Functions

Events

Cable Interaction Component RAC Cable Interaction

Both cable types - Detects, grabs, and cuts both. Pinning and extend/retract are Cable Actor only.

Player component for cable interaction: grab, drag, pin, cut, extend/retract. Supports two detection modes: Proximity (overlap radius, best for top-down) or Aim (camera crosshair ray, best for first/third person). All actions work identically in both modes.

Functions

Pinning Cable Actor

Cutting

Queries

Events

Sweep Cut

Move your aim (or player position) across cables to slice through them in one motion. Detects and cuts both Cable Actors and Wrapping Cables. Cables are cut when they enter the sweep radius, not while standing still. Works with both Aim and Proximity detection modes. See Cable Cutting for setup and general cutting info.

Swing Component RAC Swing

Grapple rope swing. Fires an aim trace from the character's camera to find a pivot point, spawns a temporary Verlet cable rope, and applies pendulum physics. Supports pump-swing (player input increases amplitude), rope reel-in/let-out, launch velocity boost on release, and configurable rope visuals. Tick disabled until swing starts.

Functions

Events

Pull Component RAC Pull

Pull physics objects toward the owner. Fires an aim trace from the character's camera, attaches a rope to the hit physics object, and applies mass-compensated force to reel it in. Supports mass limits, arrival detection, and duration caps. Tick disabled when idle.

Functions

Events

Climb Component RAC Climb

Rope climbing component. Aim trace from the camera to find a cable, grab on, and climb up or down. Gravity-based sliding when idle, optional stamina system, launch velocity on release. Works with both ARACCable and ARACWrappingCable. Zero-cost when idle (tick disabled).

Functions

Events

Tow Component RAC Tow

Spawns a cable with physics coupling between the owning actor and a target. Spring forces pull the towed target along. Supports break force, stretch limits, and tension events. Tick disabled when idle.

Functions

Events

Tow Target RAC Tow Target

Place on any actor (vehicle, prop, crate) so that the Tow Component can find it via AttachTowToNearest or the static discovery functions. Configure AttachSocket and AttachOffset to control where the tow cable attaches.

Functions

Events

Verlet Cable Component RAC Verlet Cable

The core physics solver. Simulates particles connected by distance constraints with Verlet integration. Used directly for beams/lasers, or wrapped by the Cable actor for full-featured cables.

Functions

Cutting

Pinning

Static (Global)

Niagara Integration

RAC exposes cable particle positions to Niagara via a custom Data Interface (RAC Cable Niagara DI). A sample Niagara system (NS_CableParticle) is included - duplicate it and customize, or build your own from scratch.

Cable-Side Setup

On the cable's VerletCable component:

1. Check bFeedNiagara
2. Set NiagaraSystem to your Niagara system asset
3. The cable auto-creates a NiagaraComponent at BeginPlay, discovers itself via attachment, and the DI caches positions every tick

Niagara System Setup (Step-by-Step)

You need to create a Niagara system that reads from the RAC Cable Data Interface. This requires familiarity with the Niagara editor.

1. Create a Niagara System (empty system, add an empty emitter)
2. Add User Parameters at the system level:
   • Type "RAC Cable Particles" (under Data Interface), name it CableSource
   • Type int32, name it NumPoints, default 21
3. Emitter Properties: Sim Target = CPU, enable Requires Persistent IDs
4. Emitter Update: Add Spawn Burst Instantaneous, link Count to NumPoints
5. Particle Spawn:
   • Add Initialize Particle (set Lifetime = 99999)
   • Add Set Particles.RibbonLinkOrder = Execution Index (if using Ribbon Renderer)
6. Particle Update: Add a Scratch Pad Module:
   • Add input: type RAC Cable Particles (DI), name CableSource
   • In the graph: drag CableSource into Map Get, pull wire to GetParticlePosition node
   • Wire Execution Index to the Index input
   • Wire Position output to Map Set → Particles.Position
   • Outside the Scratch Pad: link CableSource input to User.CableSource
7. Render: Add a Ribbon Renderer (set CurveTension = 1.0 for sharp tracking) or Sprite Renderer
8. Save the system