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Asked: 2025-06-05T22:14:08+05:30

Why does my CapsuleCollider2D trigger fail to register hits when both player and enemy are stationary in Unity?

I’m running into a frustrating issue with the CapsuleCollider2D trigger in my Unity project, and I could really use some help from anyone who has dealt with this kind of thing before. I’m currently working on a simple attack system for my first game, where I have a player character that can deal damage to enemies with an attack button.

Here’s the setup: I have a game object (the player) that has a CapsuleCollider2D as a child that acts as the attack hitbox. When the player presses the attack button, I activate this trigger hitbox and check if it overlaps with any game objects that have health components. If they do, the game object should take damage. The problem I’m encountering is that the trigger hitbox only seems to register collisions when either the player or the enemy is moving. If both are stationary, nothing happens.

I’ve gone over my C# script to make sure it’s checking for collisions correctly, but I can’t figure out what’s wrong. Here’s the relevant part of the code:

“`csharp
private void OnTriggerEnter2D(Collider2D collider)
{
if (collider.GetComponent() != null);
{
Health health = collider.GetComponent();
health.Damage(damage);
}
}
“`

I’m a bit confused about the logic I have here. Is there something wrong with how I’m trying to detect the collision? I’ve checked the Unity settings too, and everything seems fine. The CapsuleCollider2D is set to “Is Trigger,” and the layers are set up correctly.

Has anyone experienced something like this? Is there a specific reason why the trigger would only work when one of the objects is in motion? I also wonder if it might have something to do with the physics settings or maybe how Unity handles collisions with stationary objects. Any insights or suggestions would be really appreciated! It’s really holding up my progress, and I’m eager to get this attack system working as intended. Thanks in advance!

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    2 Answers

    1. Unity CapsuleCollider2D Trigger Issue

      It sounds like you’re running into a pretty common issue with triggers in Unity! From what you’ve described, it seems like there’s a small mistake in the collision detection part of your code.

      Your OnTriggerEnter2D method has a semicolon right after the if statement, which ends the if condition prematurely. This means the code inside the { } will run regardless of whether the condition is met or not. Here’s how you should write that part:

      private void OnTriggerEnter2D(Collider2D collider)
    {
        if (collider.GetComponent() != null)
        {
            Health health = collider.GetComponent();
            health.Damage(damage);
        }
    }

      Remove the semicolon after the if condition, and it should start working properly!

      Also, you mentioned that the trigger only works when one of the objects is moving. This is sometimes related to the physics settings in Unity. If two objects are both static and don’t move, the physics engine might not register them touching. So, making sure at least one object is dynamic or checking for potential overlaps more effectively would help.

      Make sure that the CapsuleCollider2D’s “Is Trigger” checkbox is checked, and your layers and physics settings are properly configured. If everything looks good and it still doesn’t work, you might want to reconsider how you’re organizing your game objects or check your project settings again.

      I hope this helps get your attack system up and running smoothly!

    2. The root cause of your issue is due to relying solely on the OnTriggerEnter2D method, which triggers only when at least one of the colliders involved moves or changes state. If both the player and the enemy are stationary, no collision events will fire, causing your attack detection to fail when neither is moving. Additionally, your provided code snippet contains a small but critical syntax mistake: there is an unwanted semicolon right after the if condition. This causes your if check to execute improperly and your collision logic to run regardless of the condition’s result.

      To fix these issues, first remove the unnecessary semicolon: if (collider.GetComponent<Health>() != null). Next, consider using OnTriggerStay2D instead, as this method continuously checks for existing trigger collisions each frame, allowing collision detection between stationary objects. Alternatively, you can manually call methods like Physics2D.OverlapCapsule during your attack animation to reliably detect collisions at the precise moment the attack occurs. Ensuring that the collider is enabled and properly registered within Unity’s physics system is crucial for accurate collision detection, so verifying physics layers and collision matrix settings can also help resolve inconsistencies you might encounter.