Creating custom vehicles

Vehicle Physics Pro includes VPVehicleController, a full-featured vehicle controller ready for simulating most types of vehicles. If you need a kind of vehicle not supported by VPVehicleController then you can write your own vehicle controller easily.

A vehicle controller derives from VehiclePhysics.VehicleBase. It implements the logic of the vehicle by overriding the virtual methods and instancing and connecting the Blocks representing the internal parts of the vehicle.

The virtual methods in VehiclePhysics.VehicleBase and their roles are detailed in VehicleBase reference.

Example source code

This is the most basic 4-wheeled vehicle in Vehicle Physics Pro that includes steering, brakes and rear-powered wheels.

graph RL subgraph SimpleVehicleController subgraph Wheels WFL>Wheel Front Left] WFR>Wheel Front Right] WRL>Wheel Rear Left] WRR>Wheel Rear Right] end %% Trick for making them appear first WFL WFR Eng(Direct Drive Motor) Diff{Differential} Eng-->Diff Diff-->WRL Diff-->WRR end

The drive power is provided by a direct drive motor (think on an ideal electric engine) that provides up to a maximum torque (maxDriveTorque) and can reach a maximum RPMs (maxDriveRpm). Rear wheels are connected to the direct drive with a differential in the default configuration (Open). Steering, Brakes and Tires are parts of the Wheel blocks.

This example doesn't make use of the data bus. Instead, it exposes the properties driveInput, brakeInput and steerInput. The SimpleVehicleControllerInput.cs script reads the standard Unity Input and modifies these properties for controlling the vehicle.

SimpleVehicleController.cs

using UnityEngine;
using VehiclePhysics;

public class SimpleVehicleController : VehicleBase
    {
    [Header("Simple Vehicle Controller")]
    public VPWheelCollider wheelFL;
    public VPWheelCollider wheelFR;
    public VPWheelCollider wheelRL;
    public VPWheelCollider wheelRR;
    public TireFriction tireFriction = new TireFriction();

    public float maxDriveTorque = 500.0f;
    public float maxBrakeTorque = 1000.0f;
    public float maxSteerAngle = 45.0f;
    public float maxDriveRpm = 50.0f;

    [Range(-1,1)]
    public float driveInput = 0.0f;
    [Range(0,1)]
    public float brakeInput = 0.0f;
    [Range(-1,1)]
    public float steerInput = 0.0f;

    // Internal vehicle blocks for the powertrain

    DirectDrive m_directDrive;
    Differential m_differential;

    // Initialize the controller and blocks

    protected override void OnInitialize ()
        {
        // Declare the number of wheels

        SetNumberOfWheels(4);

        if (wheelFL == null || wheelFR == null || wheelRL == null || wheelRR == null)
            {
            Debug.LogError("Missing VPWheelCollider");
            return;
            }

        // Configure mandatory data per wheel

        ConfigureWheelData(wheelState[0], wheels[0], wheelFL, true);
        ConfigureWheelData(wheelState[1], wheels[1], wheelFR, true);
        ConfigureWheelData(wheelState[2], wheels[2], wheelRL);
        ConfigureWheelData(wheelState[3], wheels[3], wheelRR);

        // Initialize and connect the blocks: DriveLine -> Differential -> Rear wheels

        m_directDrive = new DirectDrive();
        m_differential = new Differential();
        m_differential.settings.gearRatio = 1.0f;

        Block.Connect(wheels[2], 0, m_differential, 0);
        Block.Connect(wheels[3], 0, m_differential, 1);
        Block.Connect(m_differential, 0, m_directDrive, 0);
        }

    // WheelState and Wheel objects must be initialized with a minimum data per wheel

    void ConfigureWheelData (WheelState ws, Wheel wheel, VPWheelCollider wheelCol, bool steerable = false)
        {
        ws.wheelCol = wheelCol;
        ws.steerable = steerable;
        wheel.tireFriction = tireFriction;
        wheel.radius = wheelCol.radius;
        wheel.mass = wheelCol.mass;
        }

    // Set up the state values at the blocks, tires, etc.

    protected override void DoUpdateBlocks ()
        {
        // Feed the DirectDrive with the values and input from the controller's properties

        m_directDrive.motorInput = driveInput;
        m_directDrive.maxMotorTorque = maxDriveTorque;
        m_directDrive.maxRpm = maxDriveRpm;

        // Apply steering

        float angle = steerInput * maxSteerAngle;
        wheelState[0].steerAngle = angle;
        wheelState[1].steerAngle = angle;

        // Set the brakes at the Wheel blocks

        float brakeTorque = brakeInput * maxBrakeTorque;
        wheels[0].AddBrakeTorque(brakeTorque);
        wheels[1].AddBrakeTorque(brakeTorque);
        wheels[2].AddBrakeTorque(brakeTorque);
        wheels[3].AddBrakeTorque(brakeTorque);
        }
    }

SimpleVehicleControllerInput.cs

using UnityEngine;
using VehiclePhysics;

public class SimpleVehicleControllerInput : VehicleBehaviour
    {
    SimpleVehicleController m_vehicle;

    public override void OnEnableVehicle ()
        {
        // This component requires a SimpleVehicleController explicitly

        m_vehicle = vehicle.GetComponent<SimpleVehicleController>();
        if (m_vehicle == null)
            {
            DebugLogWarning("A vehicle based on SimpleVehicleController is required. Component disabled.");
            enabled = false;
            }
        }

    public override void UpdateVehicle ()
        {
        // Read the input from the standard Unity Input

        float steerInput = Mathf.Clamp(Input.GetAxis("Horizontal"), -1.0f, 1.0f);

        float throttleAndBrakeAxisValue = Input.GetAxis("Vertical");
        float throttleInput = Mathf.Clamp01(throttleAndBrakeAxisValue);
        float brakeInput = Mathf.Clamp01(-throttleAndBrakeAxisValue);

        // Hold Ctrl and Brake for reverse

        if (Input.GetKey(KeyCode.LeftControl) || Input.GetKey(KeyCode.RightControl))
            {
            throttleInput = -brakeInput;
            brakeInput = 0.0f;
            }

        // Feed the vehicle input parameters with the result

        m_vehicle.steerInput = steerInput;
        m_vehicle.driveInput = throttleInput;
        m_vehicle.brakeInput = brakeInput;
        }
    }