I am trying to detect whether or not a tree i had randomly spawn on the map spawned on top of a tile

Unity Engine
,
1

I have a “flora” script attached to the trees and i got a solution working that checks its

 OnCollisionStay ```private void OnCollisionStay2D(Collision2D collision)
    {
        if(collision.gameObject.tag == "collisionMap")
        {
           Destroy(gameObject);
        }
    }```

but I want it to work with an extra function that gets called on the three object after I instantiate it in my Populate world script here

```public void spawnTrees()
    {
        for(int i = 0; i <= amountTrees; i++ )
        {
            Vector3 pos = center + new Vector3(Random.Range(-size.x / 2, size.x / 2), Random.Range(-size.x / 2, size.x / 2), 0);        
            GameObject tree = Instantiate(tree1, pos, Quaternion.identity);
            tree.GetComponent<Flora>().checkCollision();
        }
    
    }

so it can eventually give feedback if the tree spawned properly and this attempt:

   public void checkCollision()
    {
        Vector2 origin = new Vector2(myCollider.transform.position.x, myCollider.transform.position.y);
        Vector2 size = new Vector2(myCollider.bounds.size.x, myCollider.bounds.size.y);
        RaycastHit2D raycast = Physics2D.BoxCast(origin, size, 0f, Vector2.right, 1f);
        if(raycast.collider != null) Debug.Log(raycast.collider.tag);
    }

just did not register any collision and I dont know why.

2

The casting should work fine, ASSUMING you are casting properly at something that can be casted at.

To figure out why it is not, strip it down and do the standard debugging, one known collider in a known location, do the cast, verify it works.

However, beware that the OnCollisionStay2D() will NOT be called at that instant, for the simple reason that those calls only happen at a very specific step of the Unity update loop:

Here is some timing diagram help:

https://docs.unity3d.com/Manual/ExecutionOrder.html

Whatever it is, you must find a way to get the information you need in order to reason about what the problem is.

What is often happening in these cases is one of the following:

  • the code you think is executing is not actually executing at all
  • the code is executing far EARLIER or LATER than you think
  • the code is executing far LESS OFTEN than you think
  • the code is executing far MORE OFTEN than you think
  • the code is executing on another GameObject than you think it is

To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

  • is this code even running? which parts are running? how often does it run? what order does it run in?
  • what are the values of the variables involved? Are they initialized? Are the values reasonable?
  • are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

You can also put in Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

If you are running a mobile device you can also view the console output. Google for how on your particular mobile target.

Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

https://discussions.unity.com/t/839300/3