Wheel API: RCCP 1 to RCCP 2

01Read a wheel from code

Use RCCP_WheelCollider as the wheel facade, the public interface to the wheel system. The component owns its geometry, suspension and friction settings. New wheels do not need a Unity WheelCollider. Read the simulation results through this component.

Put this method in your component. Give the method the wheel facade that you want to examine.

using BoneCrackerGames;
void ReadWheel(RCCP_WheelCollider wheel) {
    if (wheel == null) return;
    float rpm = wheel.Rpm;
    bool grounded = wheel.IsGrounded;
    if (grounded && wheel.GetGroundHit(out UnityEngine.WheelHit hit))
        UnityEngine.Debug.Log($"RPM: {rpm}, suspension force: {hit.force} N");
}

The solver publishes contact, spin, slip and force results after each solve. To read results in the same step in FixedUpdate, obey the execution order.

For usual driving, use the input API. For setup in the Inspector, use Wheels and tires.

02Old wheel access and its replacement

In this table, wheel is an RCCP_WheelCollider. The first column shows old native access. Use the first column only for migration.

The suspension and force-height setters also request a solver settings refresh. To change the configuration, use these properties or SetWheelSettings.

Geometry, mass, springs and source friction curves give the solver configuration. When the settings revision of the facade changes, the solver refreshes its converted settings. The RCCP component keeps the source friction curves. The solver publishes the live force and slip outputs separately.

A changed source curve can calculate its tire axis again. Unchanged curves keep the authored tire values. This rule also applies to curves that behavior presets write. See the preset workflow.

For a custom drivetrain, obey the accumulator pipeline. Usual driving uses throttle, brake and steering inputs.

03New wheel readouts

These read-only properties give the solver results.

Compatibility slip uses a different scale from the physical solver values above.

After the next fixed step of a detached wheel, isGrounded and isSkidding are false, and wheelHit is empty. The HubPosition of a detached wheel returns the position of the wheel object.

04Wheel data from code

To edit wheel data from code, get a copy from EffectiveWheelData. Change the copy, then give the copy to SetWheelData. In editor code, record Undo before you change authored data. If the wheel is in a prefab instance, record the prefab instance modifications.

CAUTION: Back up the wheel tuning before you call MigrateWheelData(true). The call replaces the saved wheel data with a new conversion. The current wheel tuning can be lost.

For the editor upgrade procedure, see Old wheel data. For installation changes, see the upgrade guide.

05Obsolete wheel settings

The wheel solver selects its substeps automatically. These old profile controls do not select solver substeps.

The Substeps setting of the damage solver (RCCP_DeformationSolver.substeps) is still active. That setting controls the dent simulation, not wheel profiles.

You can still call these deprecated wheel aliases:

engineBrakeTorqueNm goes back to zero in the FixedUpdate of the wheel at order 0. Thus Update and LateUpdate read zero. For haptics, read the value in a component with [DefaultExecutionOrder(-1)]. Keep that value for your later haptic update.

06Reset wheel state

A reset clears the spin, slip, contact and suspension memory before the next solve. The readouts do not change immediately when you request a reset.

Transport requests this reset, also for calls with resetVelocity: false. The replay director requests resets at playback start, live resume, direction changes, seeks and replay exit. Recorder playback also requests a reset when it moves the vehicle to the first recorded pose. Wheel spin and slip are not continuous across these operations.

See Transport and Instant replay for the entry points.