Object not responding to OnTriggerEnter()

Questions & Answers
1

So I’m trying to get a car to respawn at a general location some short time after passing a collider. For some reason, the script works if I walk into the collider with FirstPersonController. However it won’t affect the car. Interestingly, if I test carReset() with “p” as shown in Update() after the car passes the collider, I get the error: “NullReferenceException: Object reference not set to an instance of an object”. I’m fairly new to scripting and unity and I can’t figure out why this wouldn’t be working but still affects FirstPersonController.

Here’s the script:

public class CarRespawn : MonoBehaviour {
	GameObject car;

	void Update(){
		if (Input.GetKeyDown ("p")) {
			carReset ();
		}
	}

	void OnTriggerEnter(Collider c_car){
		car = c_car.gameObject;
		Invoke ("carReset", Random.Range (0.5f, 3.0f));
	}

	void carReset(){
		car.transform.position = new Vector3 (Random.Range (-6.0f, -12.0f), 1.16f, Random.Range(25.0f, 60.0f) );
	}
}
2

Ok, So this is what i did. You need 1 car with a Rigidbody. 1 Barrier with a box collider that has Is Trigger enabled. Then use the code below and attach that to the barrier.

using UnityEngine;

public class TriggerEnter : MonoBehaviour
{
    GameObject car;

    private void OnTriggerEnter(Collider other)
    {
        if (other.name == "Car" || other.gameObject.tag == "Car")
        {
            Debug.Log("Hit");
            car = other.gameObject;
            Invoke("ResetCar", Random.Range(0.5f, 3f));
        }
    }

    private void ResetCar()
    {
        car.transform.position = new Vector3(Random.Range(6.0f, -12.0f), 1.16f, Random.Range(25.0f, -60.0f));
    }
}

Note: The car must be named “Car” or have a tag called “Car”

That’s it. It moves the car when it hits the barrier. I’m expecting that your problem was that the car didn’t have a rigidbody.

The null reference exception was due to the fact that your car never actually registered as hitting the collider, and so it never assigned the car.

3

@JaredHD Ah alright, thanks! So to be clear, the collider won’t be detected unless the object it’s attached to also has a rigidbody? Why is that?