How to add a spawner on a side of moving camera in unity2D - unity3d

Question

I'm creating a 2D racing game in Unity2D and unsure how to approach on coding my spawner for objects e.g. power-up, rewards and obstacles ahead on the right side of my moving camera. The camera follows my vehicle and moves from left to right. Currently objects spawn in the game, but only spawn on a point and continue to spawn in the same point when the camera has scrolled way past. Apologies, if the answer was simple.
Here are the scripts I used:
coin.cs is attached to my coin prefab
public class coin : MonoBehaviour
{
public Camera mainCamera;
Rigidbody2D rb;
// Start is called before the first frame update
void Start()
{
mainCamera = GameObject.FindObjectOfType<Camera>();
rb = this.gameObject.GetComponent<Rigidbody2D>();
transform.position = new Vector2(mainCamera.pixelWidth / 32, getRandomHeight());
}
float getRandomHeight(){
return Random.Range(-(mainCamera.pixelHeight / 2) / 100, (mainCamera.pixelHeight / 2) / 100);
}
private void OnTriggerEnter(Collider coll){
if (coll.gameObject.tag == "Player"){
Destroy(this.gameObject);
}
}
// Update is called once per frame
void Update()
{}
}
and coinSpawner.cs is attached to a gameObject in the scene
public class coinSpawner : MonoBehaviour
{
float LastSpawnTime = -500f;
float NextSpawnTime = 3;
public Object CoinPrefab; // declare coinPrefab
// Start is called before the first frame update
void Start()
{
}
// Update is called once per frame
void Update()
{
if (Time.time - LastSpawnTime > NextSpawnTime)
{
NextSpawnTime = Random.Range(3, 10);
LastSpawnTime = Time.time;
Instantiate(CoinPrefab);
}
}

Answer 1

Instantiate(CoinPrefab);
spawns this object without any information of position or parent object. This it will always be spawned at Scene root and 0,0,0.
Then this line
transform.position = new Vector2(mainCamera.pixelWidth / 32, getRandomHeight());
in coin always places it to the absolute position depending on your pixelWidth which doesn't change over time.
You are saying the Camera is moving so you should rather take it's transform.position into account.
You have basically two(three) ways to go here:
You can make the spawner GameObject a child of your Camera - so it is automatically moved along with it - and move it to the right to have the desired offset. Then simply spawn new objects at this GameObjects position. Then you can do it in coinSpawner:
Instantiate(CoinPrefab, transform.position, Quaternion.Identity);
Or get the Camera reference and use it's position + the desired offset either also only in coinSpawner like
// reference this already via the Inspector if possible
[SerializeField] Camera _camera;
// Otherwise get the reference on runtime
void Awake()
{
if(!_camera)_camera = Camera.main;
}
float getRandomHeight => Random.Range(-(_camera.pixelHeight / 2) / 100, (_camera.pixelHeight / 2) / 100;
and then do something like
Instantiate(CoinPrefab, new Vector2(_camera.transform.position.x + mainCamera.pixelWidth / 32, getRandomHeight()), Quaternion.Identity);
This would actually be more efficient since the entire coin script would be reduced to only the OnTriggerEnter part and not every coin would use FindObjectOfType and GetComponent when spawned.
Basically the same as above but sticking to your code structure simply do
transform.position = new Vector2(mainCamera.transform.position.x + mainCamera.pixelWidth / 32, getRandomHeight());
I wouldn't do it this way though due to efficiency as said.