Creating add-on components

You may write an add-component for your vehicles easily by deriving from VehicleBehaviour instead of MonoBehaviour. VehicleBehaviours are similar to standard MonoBehaviour components, but they expose virtual methods that are invoked in sync with the vehicle's state. VehicleBehaviours may be added anywhere in the hierarchy of the vehicle.

Other events are available. Check out VehicleBehaviour reference for full details.

Never override OnEnable or OnDisable in a VehicleBehaviour! Use OnEnableComponent and OnDisableComponent instead if you need to trace the initialization of the component in Unity.

Example source code


using UnityEngine;
using UnityEngine.UI;
using VehiclePhysics;

public class SimpleVehicleAddon : VehicleBehaviour
    public Text uiText;

    public override void OnEnableVehicle ()
        // Check for the component initialization conditions.
        // If they're not met the component gracefully terminates here.

        if (uiText == null)
            DebugLogError("This component requires an UI Text label. Component disabled.");
            enabled = false;

        Debug.Log("Vehicle enabled. " + vehicle.wheelCount + " wheels");

    public override void OnDisableVehicle ()
        uiText.text = "";

        Debug.Log("Vehicle disabled");

    public override void UpdateVehicle ()
        // Read the RPMs of all the wheels and display them in the UI label.

        string text = "";

        for (int i = 0; i < vehicle.wheelState.Length; i++)
            VehicleBase.WheelState ws = vehicle.wheelState[i];

            text += string.Format("{0}:  {1:0.}\n",, ws.angularVelocity * Block.WToRpm);

        uiText.text = text;