Car Spinning Out When Reversing

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1

I am working on a Unity 3D car controller, and everything is looking good except for when I reverse. When I try to steer when reversing, if I steer in one direction for too long, the car will spin out about 180 degrees. I have tried to fix this, but none of my solutions are working. Attached below is my code:

using UnityEngine;

public class CarControl : MonoBehaviour
{
    public float motorTorque = 2000;
    public float brakeTorque = 2000;
    public float maxSpeed = 20;
    public float maxReverseSpeed = 10;
    public float steeringRange = 30;
    public float steeringRangeAtMaxSpeed = 10;
    public float velocityThreshold = 0.1f;
    public float centreOfGravityOffset = -1f;

    WheelControl[] wheels;
    Rigidbody rb;

    // Start is called before the first frame update
    void Start()
    {
        rb = GetComponent<Rigidbody>();

        // Adjust center of mass vertically, to help prevent the car from rolling
        rb.centerOfMass += Vector3.up * centreOfGravityOffset;

        // Find all child GameObjects that have the WheelControl script attached
        wheels = GetComponentsInChildren<WheelControl>();
    }

    // Update is called once per frame
    void Update()
    {

        float speedFactor;
        float currentSteerRange;

        float vertical = Input.GetAxis("Vertical");
        float horizontal = Input.GetAxis("Horizontal");

        // Calculate current speed in relation to the forward direction of the car
        // (this returns a negative number when traveling backwards)
        float forwardSpeed = Vector3.Dot(transform.forward, rb.velocity);


        // Calculate how close the car is to top speed
        // as a number from zero to one
        speedFactor = Mathf.InverseLerp(0, maxSpeed, forwardSpeed);

        // Use that to calculate how much torque is available 
        // (zero torque at top speed, b/c car is at the max speed so no more torque should be there)
        float currentMotorTorque = Mathf.Lerp(motorTorque, 0, speedFactor);

        // and to calculate how much to steer 
        // (the car steers more gently at top speed)
        currentSteerRange = Mathf.Lerp(steeringRange, steeringRangeAtMaxSpeed, speedFactor);

        // Check whether the user input is in the same direction 
        // as the car's velocity
        bool isAccelerating = Mathf.Sign(vertical) == Mathf.Sign(forwardSpeed);

        foreach (var wheel in wheels)
        {
            // Apply steering to Wheel colliders that have "Steerable" enabled
            if (wheel.steerable)
            {
                wheel.WheelCollider.steerAngle = horizontal * currentSteerRange;
            }
            
            if (isAccelerating)
            {
                // Apply torque to Wheel colliders that have "Motorized" enabled
                if (wheel.motorized)
                {
                    wheel.WheelCollider.motorTorque = vertical * currentMotorTorque;
                }
                wheel.WheelCollider.brakeTorque = 0;
            }
            else
            {
                // If the user is trying to go in the opposite direction
                // apply brakes to all wheels
                wheel.WheelCollider.brakeTorque = Mathf.Abs(vertical) * brakeTorque;
                wheel.WheelCollider.motorTorque = 0;
            }

            if(Input.GetKey(KeyCode.Space))
            {
                wheel.WheelCollider.brakeTorque += brakeTorque;
            }
        }
    }
}

2 Answers

2
3

Thanks for the reply! I filed a bug report with the repro project. The case number is: [IN-70944]

2

Unfortunately it’s hard to tell what the cause of the spin-out is just from this code, as it could be related to a number of other components in the construction of your physics vehicle.

Could you put together a small repro project and file a bug report with that project, then share the case number here.