Magnet street - How car object can follow the street in real world physic

Unity Engine
1

Good evening everyone. As you can see from the image I would like to make sure that my car was able to travel this road by making this 360-degree turn while remaining glued to the asphalt. could anyone suggest me which approach to use and / or which script achieves this effect?

6951545--817886--Schermata 2021-03-18 alle 18.44.37.jpg
6951545--817886--Schermata 2021-03-18 alle 18.44.37.jpg2820Ă—1532 236 KB

2

You can disable gravity in the car’s rigidbody and apply the gravity force via AddForce in the direction of the road.

rigidbody.AddForce(gravityDirection * 9.81f, ForceMode.Acceleration);

Here you would need to calculate gravityDirection as the normalized “down” direction with respect to the road.

PS. I love that stunt. The only game I know that includes it is the good old Fatal Racing for PC. I think it could be done without gravity tricks if the car travels it at enough speed in a precise direction. Testing it in Unity with a proper simulation is one of my pending tasks :wink:

How did you modeled the track? Some asset, or directly in a 3D tool?

1 Like
3

Thank you so much for the advice. Having such a tight propeller and little space to apply it let’s say I can’t help but take the gravity out (even if the game has real physics). As for the track I started from these assets Simple Racer - Cartoon Assets | 3D Land | Unity Asset Store but I am doing a lot of things using Blender. For example, this screw is not part of the package and I made it myself with very little knowledge of Blender.

I finally solved the problem by writing this short script for my machine and I have to tell you that it works really well :slight_smile:

    void AttractorCheck()
    {
        int layerMask = 1 << 8;

        layerMask = ~layerMask;

        RaycastHit hit;
        if (Physics.Raycast(RayCastTransf.position, transform.TransformDirection(Vector3.down), out hit, 5, layerMask) && hit.transform.CompareTag("AttractionLayer"))
        {
            Debug.DrawRay(RayCastTransf.position, transform.TransformDirection(Vector3.down) * hit.distance, Color.yellow);
            _rb.useGravity = false;
            ApplyStabilizer(hit.normal);
            _rb.AddRelativeForce(Vector3.down * 10000 * attractionSpeed * Time.fixedDeltaTime);

        }
        else
        {
            Debug.DrawRay(RayCastTransf.position, transform.TransformDirection(Vector3.down) * 5, Color.white);
            _rb.useGravity = true;
            ApplyStabilizer(Vector3.up);
        }
    }
4

If I can exploit your answer and this psot I want to ask you what is the best way for you to turn left and right with the car, I am having a lot of problems because I can’t find the nicest way to move the car. right now my approach is to evaluate a function based on horizontal key presses, only the effect is not that great. Do you have any proposals for scripts to use? I leave you below mine:

[SerializeField] AnimationCurve turnInputCurve = AnimationCurve.Linear(-1.0f, -0.3f, 1.0f, 0.3f);

    void FixedUpdate()
    {
steering = turnInputCurve.Evaluate(GetInput(turnInput)) * steerAngle;

        // Direction
        foreach (WheelCollider wheel in turnWheel)
        {
            wheel.steerAngle = Mathf.Lerp(wheel.steerAngle, steering, steerSpeed);
        }

}
5

Thank you for the info!

Hint: you can replace “trasform.TransformDirection(Vector3.down)” with “-transform.up”.

I’d simply use:

wheel.steerAngle = Input.GetAxis("Horizontal");

Then I’d configure the Horizontal input in the Input Manager. Here’s a setup that works pretty good to me:
https://evp.vehiclephysics.com/faq/#how-to-configure-the-input-parameters

1 Like
6

Nice!
I had some luck with a “magnetic flying cube” by changing the global Physics.gravity (in your case, I guess, to the normal of the centreline of the road):

Hmm, thinking about it, for proper glue, I guess maybe I’d need to increase the gravity magnitude too.
Well, you anyway have a solution and your game looks great:)

1 Like
7

If anyone is here in the future, I wanted to share the package with the solution to the problem. All can be downloaded easily from my personal GitHub. :slight_smile:

1 Like