Rolling FX and audio

A tyre on gravel sounds like gravel, on mud it throws mud, and on snow it makes its own hiss. The plugin plays each wheel’s rolling sound and shows its rolling effect from the surface under that wheel. The sound and effect grow with speed, and braking makes the effect throw harder. This page covers how those follow the ground, how to tune them, and how to add your own surface.

Rolling Sound
Rolling Sound
Attenuation	SA_CF_TireRolling
Sound Class	None
Priority	0.1
Speed Parameter Name	Speed
Tuning
Cabin Volume Scale	0.8
Cabin Low Pass Frequency	3000.0 Hz
Rolling FX
Rolling FX
FX Intensity Parameter	Intensity
FX Tuning

The Rolling Sound and Rolling FX groups in Project Settings, under Plugins > Crushform Wheels.

What it does

Every wheel has its own rolling sound and rolling effect. Each one follows the surface under its wheel and fades in as the wheel speeds up. The sound is the surface’s rolling loop, and the effect is the surface’s Niagara system. Both are presentation only: they play on every machine that renders the vehicle, and a dedicated server plays neither.

Braking on the MUD lane: the mud rolling effect throws mud behind the wheels.

How it works

• Two components. UCFRollingAudioComponent plays the rolling sound and UCFRollingFXComponent shows the effect. The vehicle adapter creates them under the Rolling Sound and Rolling FX flags. Each of the two reads the wheels from the vehicle’s host and works per wheel.
• Sound per wheel. Each wheel has a voice, which follows the rolling sound of the surface under it and crossfades to a new one once that surface has held under the wheel for Surface Hold Time. The volume fades in linearly from Min Audible Speed KPH to Full Volume Speed KPH, and the pitch rises from Pitch at Min Speed to Pitch at Full Speed at Full Pitch Speed KPH. A small random pitch offset keeps identical wheels from playing in phase.
• Hearing. A wheel is silent unless a listener is within reach of the attenuation, so a distant vehicle stays quiet.
• Effect per wheel. The effect is a Niagara system, one per wheel, taken from the surface’s row. Its intensity is the wheel or vehicle speed over Full Intensity Speed KPH, up to 1, times Brake Boost while the wheel brakes. Braking, set with SetBraking, raises it past 1 up to that boost.
• Sleep. Every effect of the vehicle stops while the body and its fastest grounded wheel are both slower than Sleep Speed KPH. A car stuck in mud keeps its effect, because its spinning wheel is fast.
• Cabin. SetCabinMuffled on the adapter lowers the rolling sound for a listener inside the cabin: the volume is multiplied by Cabin Volume Scale and a low-pass filter cuts above Cabin Low Pass Frequency. The same call muffles the engine sound when the adapter has one, which the Engine sound page covers. Nothing calls it for you, so the game tells the adapter when the listener is in the cabin.
• Settings. The defaults for every vehicle are in Project Settings > Plugins > Crushform Wheels. A vehicle can override the sound tuning and the effect tuning on its adapter, or on the component itself.

Set it up

1. In Project Settings > Plugins > Crushform Wheels, check Attenuation. It is SA_CF_TireRolling by default. Set Sound Class if you have one. Leave it empty for the default class.
2. In your surfaces table, give each row a Rolling Sound and a Rolling FX. A sound must be a looping asset (see Troubleshooting). See Wheels and surfaces for the table.
3. On the vehicle’s adapter, tick Rolling Sound and Rolling FX. Both are on by default.
4. To make your own effect, create a Niagara system with a float user parameter named Intensity, which is the project’s default. Set it as Rolling FX on a row. If the parameter has another name, set Rolling FX Intensity Parameter on that row to its name.
5. To tune a single vehicle, tick Override Rolling Sound Tuning or Override Rolling FX Tuning on its adapter and set the values there.

Use it

Brake from Blueprint with the adapter’s Set Braking, from 0 to 1. Muffle the cabin with Set Cabin Muffled when the listener enters or leaves the car. The graph below runs when the custom event SetCabinState fires, muffles the cabin and then sets the brake to full.

SetCabinState

Output Delegate

CF Adapter

CF Adapter

Set Cabin MuffledTarget is CFVehicle Adapter Component

Target

Muffled

Set BrakingTarget is CFVehicle Adapter Component

Target

Amount1.0

BLUEPRINT

The graph runs when the custom event SetCabinState fires, muffles the cabin and then sets the brake to full.

From C++, call the same two functions on the adapter. The calls need the CrushformVehicle module (CFVehicleAdapterComponent.h), which you add to PublicDependencyModuleNames in your module’s Build.cs.

Adapter->SetBraking(0.8f);
Adapter->SetCabinMuffled(bInCabin);

SetCabinMuffled takes the cabin values of Crushform Wheels (for the wheels) and Crushform Engine (for the engine). Tick Override Cabin Muffling on the adapter to use its own Cabin Volume Scale and Cabin Low Pass Frequency for both instead.

Key settings

Property	What it does	Default
UCFWheelSettings::bRollingSound	The master switch of the rolling sound. Off, no wheel plays one.	true
UCFWheelSettings::Attenuation	The attenuation of every rolling sound. Empty, and the sound stays off.	/Crushform/Sounds/SA_CF_TireRolling
UCFWheelSettings::SpeedParameterName	The float parameter of the sound that takes the speed in km/h. None, and the speed is not sent.	Speed
FCFRollingAudioTuning::FullVolumeSpeedKPH	The wheel speed at which the sound reaches full volume, in km/h.	50
FCFRollingAudioTuning::SurfaceHoldTime	Seconds a new surface must hold under the wheel before the sound crossfades to it.	0.15
UCFWheelSettings::CabinVolumeScale	The volume multiplier of the sound heard from the cabin.	0.8
UCFWheelSettings::CabinLowPassFrequency	The low-pass cutoff of the sound heard from the cabin, in Hz.	3000
UCFWheelSettings::bRollingFX	The master switch of the rolling effect. Off, no wheel shows one.	true
UCFWheelSettings::FXIntensityParameter	The float parameter that takes a wheel’s intensity, for a row that names none.	Intensity
FCFRollingFXTuning::FullIntensitySpeedKPH	The speed at which an effect reaches full intensity, in km/h.	40
FCFRollingFXTuning::BrakeBoost	The intensity multiplier while braking.	2
FCFRollingFXTuning::SleepSpeedKPH	The speed below which every effect of the vehicle stops, in km/h. 0 never sleeps.	1

Check that it works

Play Lvl_ProvingGround and drive the sedan from the ASPHALT strip onto the DIRT, MUD and SNOW strips. The rolling sound changes with each surface, and each wheel shows the effect of the surface under it. Brake hard on the dirt. The effect throws harder while the brakes are on. Run stat CrushformWheel to show the statistics of the wheel components.

Troubleshooting

There is no rolling sound at all

Cause. Three things silence the sound. Rolling Sound is off on the adapter or in Crushform Wheels. The Attenuation is empty, and the plugin logs it when the component begins play:

%s: no Attenuation in Project Settings > Plugins > Crushform Wheels; the rolling sound stays off

The sound is also silent on a dedicated server.

Fix. Tick Rolling Sound on the adapter, set Attenuation in Crushform Wheels, and test on a client or a listen server.

The sound is silent when the camera is far away

Cause. A wheel plays only while a listener is within reach of the attenuation’s maximum distance. This is by design, so a distant vehicle costs nothing.

Fix. Move the listener closer, or widen the attenuation’s range if the sound should carry further.

The rolling sound cuts out

Cause. The sound asset is not set to loop. The plugin logs it once per asset, when a wheel first plays it:

%s: rolling sound '%s' is not looping - it will cut out between restarts. Set bLooping on the asset.

Fix. Set Looping on the sound asset.

A surface makes a sound but shows no effect

Cause. The row’s Rolling FX is empty, or it is not a Niagara system. A wheel on such a row stops its effect.

Fix. Set Rolling FX on that row to a Niagara system, such as NS_CF_Rolling_Mud.

The effects stop while the car creeps

Cause. The effects sleep while the body and its fastest grounded wheel are both slower than Sleep Speed KPH, which is 1 km/h by default.

Fix. Lower Sleep Speed KPH in the tuning, or set it to 0 so that the effects never sleep.