2D: Detecting when player is above sprite

Unity Engine
1

I wanted to make a 2d top down game that loads and unloads chunks like minecraft. I wanted it so when the player leaves its current chunk, the chunks would unload and new ones would load. I tried to use raycasts but something is wrong, my player is affected by it while I have a layermask set to only the chunks.

Video of player being affected:

code: (from player)

private void Update()
    {
        movement.x = Input.GetAxisRaw("Horizontal");
        movement.y = Input.GetAxisRaw("Vertical");

        CheckChunks();
    }

    private void FixedUpdate()
    {
        rb.MovePosition(rb.position + movement * speed * Time.fixedDeltaTime);
    }

    void CheckChunks()
    {
        RaycastHit2D hit = Physics2D.Raycast(transform.position, Vector2.up, 1000000, 3);
        currentTile = hit.transform.gameObject;


        if (hit.transform.gameObject != currentTile)
        {
            //do something
        }

    }

I am really confused

2

Layermask is a bitmask. Each bit is a layer. 3 is bit 0 and 1 set so layer 0 and 1.

Also, you should check if the hit actually hits something before you access it. You should do:

if (hit)
{
}
1 Like
3

Here is how to find out what “something” is wrong.

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
  • you’re getting an error or warning and you haven’t noticed it in the console window

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.

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

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, such as this answer or iOS: https://discussions.unity.com/t/700551 or this answer for Android: https://discussions.unity.com/t/699654

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

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

4

I replaced the ‘3’ with LayerMask.GetMask but it is still the same, It also hits something everytime so that is not the problem.

Maybe there is another way of getting the object where the player is standing on?

5

There’s nothing wrong with Raycast, it’ll just be you using it incorrectly. There’s no need to look for alternatives. You say it “hits something everytime” so check what it does hit and then check the layers you specified and the layers of the Collider it hits. This is all the debugging you need to do.

You need to ensure your colliders are on the correct layers (check the GameObjects) and you’re specifying the correct layer-mask.

1 Like
6

I switched to oncollisionenter and it works!