Question OnTriggerEnter2D Won't Trigger Again Unless the Player Moves

Hello all,
I am trying to use a toggleable Box Collider 2D as the weapon hitbox in a top down 2D game.The sword hitbox is off by default and then is activates when the player attacks for the duration of the animation, before being disabled again at the end.

I am trying to use On Trigger Enter 2D to handle the sword hit detection, however I have run into a problem here. On the first attack everything works fine, the sword's box collider turns on, deals damage to the enemy, and is disabled again as it should be. If I attack a second time without moving though, the collider enables and disables correctly, but the OnTriggerEnter2D function is not called (I checked with debug log). If I then move my character around a little the OnTriggerEnter2D function again works like normal, until I try to attack twice without moving, where it stops detecting again.

My question is: How can I get OnTriggerEnter2D to detect my sword Box Collider and the enemy collider every time, without having to move around?

I tried OnTriggerStay2D as it should detect whenever the colliders are inside one another, but it suffers from the same issue of not working twice while stationary.

I've provided my SwordAttack script as well as my Player and Enemy controllers below. Hopefully the problem lies therein, but please let me know if there is additional material required to find the source of the bug!

Thank you all very much!

SwordAttack.cs

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class SwordAttack : MonoBehaviour
6. {
7.  
8.     public int damage = 10;
9.     public Collider2D swordCollider;
10.     Vector2 rightAttackOffset;
11.  
12.     private void Start()
13.     {
14.         rightAttackOffset = transform.position;
15.     }
16.  
17.     public void AttackRight()
18.     {
19.         print("attackRight");
20.         swordCollider.enabled = true;
21.         transform.localPosition = rightAttackOffset;
22.     }
23.  
24.     public void AttackLeft()
25.     {
26.         print("attackLeft");
27.         swordCollider.enabled = true;
28.         transform.localPosition = new Vector2(rightAttackOffset.x * -1, rightAttackOffset.y);
29.     }
30.  
31.     public void StopAttack()
32.     {
33.         swordCollider.enabled = false;
34.     }
35.  
36.     private void OnTriggerEnter2D(Collider2D other)
37.     {
38.        
39.         Debug.Log("SwordCollider hit!");
40.         if (other.tag == "Enemy")
41.         {
42.             Enemy enemy = other.GetComponent<Enemy>();
43.  
44.             if (enemy != null)
45.             {
46.                 enemy.healthSystem.DealDamage(damage);
47.             }
48.         }
49.  
50.        
51.     }
52.  
53. }
54.  

Enemy.cs

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Enemy : MonoBehaviour
6. {
7.     public HealthSystem healthSystem;
8.     public ContactAttack contactAttack;
9.     public CapsuleCollider2D enemyCollider;
10.    
11.  
12.     private void Start()
13.     {
14.        
15.     }
16.  
17.    
18.     public void RemoveEnemy() {
19.         // Called at end of death animation to remove sprite.
20.         Destroy(gameObject);
21.     }
22.  
23.     public void RemoveCollider() {
24.         // Called as soon as death animation plays to stop accidental player hits.
25.         enemyCollider.enabled = false;
26.     }
27. }
28.  

PlayerController.cs

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.InputSystem;
5.  
6. public class PlayerController : MonoBehaviour
7. {
8.  
9.     public float moveSpeed = 1f;
10.     public float collisionOffset = 0.05f;
11.     public ContactFilter2D movementFilter;
12.     public SwordAttack swordAttack;
13.     public HealthSystem healthSystem;
14.     public GameManager gameManager;
15.  
16.     Vector2 movementInput;
17.     SpriteRenderer spriteRenderer;
18.     Rigidbody2D rb;
19.     Animator animator;
20.     List<RaycastHit2D> castCollisions = new List<RaycastHit2D>();
21.  
22.     bool canMove = true;
23.  
24.     // Start is called before the first frame update
25.     void Start()
26.     {
27.         rb = GetComponent<Rigidbody2D>();
28.         animator = GetComponent<Animator>();
29.         spriteRenderer = GetComponent<SpriteRenderer>();
30.     }
31.  
32.     private void Update()
33.     {
34.  
35.     }
36.  
37.     private void FixedUpdate()
38.     {
39.         if (canMove)
40.         {
41.             // First check if we can move at all
42.             if (movementInput != Vector2.zero)
43.             {
44.                 // Then check if we can move in the xy vector we want, and move if it is free
45.                 bool success = TryMove(movementInput);
46.  
47.                 // If the vector we want is obstructed...
48.                 if (!success)
49.                 {
50.                     // First try to move in a straight X vector
51.                     success = TryMove(new Vector2(movementInput.x, 0));
52.  
53.                     // And then try to move in a straight y vector
54.                     if (!success)
55.                     {
56.                         success = TryMove(new Vector2(0, movementInput.y));
57.                     }
58.                 }
59.  
60.                 // Sets aminator flags to signal the switch between moving and attacking animations
61.                 animator.SetBool("isMoving", success);
62.             }
63.             else
64.             {
65.                 animator.SetBool("isMoving", false);
66.             }
67.  
68.             // Set direction of sprite to movement direction.
69.             if (movementInput.x < 0)
70.             {
71.                 spriteRenderer.flipX = true;
72.             }
73.             else if (movementInput.x > 0)
74.             {
75.                 spriteRenderer.flipX = false;
76.             }
77.         }
78.     }
79.  
80.     private bool TryMove(Vector2 direction)
81.     {
82.         if (direction != Vector2.zero)
83.         {
84.             int count = rb.Cast(
85.                     direction,  // X and Y values between -1 and 1 that represent the direction from the body to look for collisions.
86.                     movementFilter,  // The settings that determine where a collision can occur on, such as layers to collide with.
87.                     castCollisions,  // List of collisions to store the found collisions into, after the cast is finished.
88.                     moveSpeed * Time.fixedDeltaTime + collisionOffset);  // The amount to cast equal to the movement plus an offset. Can prevent getting stuck on terrain.
89.  
90.             if (count == 0)
91.             {
92.                 // Time.fixedDeltaTime runs physics interactions on a fixed timescale to keep things uniform if the frames aren't right.
93.                 rb.MovePosition(rb.position + moveSpeed * Time.fixedDeltaTime * direction);
94.                 return true;
95.             }
96.             else
97.             {
98.                 return false;
99.             }
100.         }
101.         else
102.         {
103.             // Can't move if there's no direction to move in
104.             return false;
105.         }
106.     }
107.  
108.     void OnMove(InputValue movementValue)
109.     {
110.         movementInput = movementValue.Get<Vector2>();
111.     }
112.  
113.     void OnFire()
114.     {
115.         animator.SetTrigger("swordAttack");
116.     }
117.  
118.     public void SwordAttack()
119.     {
120.         LockMovement();
121.  
122.         if (spriteRenderer.flipX == true){
123.             swordAttack.AttackLeft();
124.         } else {
125.             swordAttack.AttackRight();
126.         }
127.     }
128.  
129.  
130.     public void EndSwordAttack()
131.     {
132.         UnlockMovement();
133.         swordAttack.StopAttack();
134.     }
135.  
136.     public void LockMovement()
137.     {
138.         canMove = false;
139.     }
140.  
141.     public void UnlockMovement()
142.     {
143.         canMove = true;
144.     }
145.  
146.     public void PlayerDefeated() {
147.         gameManager.Restart();
148.     }
149.  
150. }
151.  

 

Hello! Maybe you have already found the solution to this problem. Anyway, I had the exact same problem. And it turned out that the solution was to set the enemy's RigidBody2D as "Dynamic" and Sleeping Mode to "Never Sleep".

 

I believe this is the tutorial @paultoth I using is and it produces the same results for me. One hit, and then you need to move the player to receive a second one. Furthermore, @Clone3 proposes the use of Sleeping Mode: Never Sleep which in fact works but was hoping for a better solution.

It may well be the tutorial somewhat messing up or something else not correctly setup, but I see the reported behavior too.

 

I'm running into the same thing, where I have:

* A tree:

    - With a static Rigidbody2D

    - And a Collider (isTrigger = false)

    - And a script containing log calls in OnTriggerEnter/Exit2D

* A player:

    - With a dynamic Rigidbody2D

    - And a Collider (isTrigger = false)

    - And a child object for the hitbox of an axe:

        o With a Collider (isTrigger = true) (initially disabled)

When running up to the tree and enabling the hitbox collider followed by disabling the hitbox collider (swinging the axe), I see my log entries for OnTriggerEnter2D and OnTriggerExit2D on the tree object.

However, when I don't move the character and press the key to enable/disable the hitbox (swinging the axe) again, OnTriggerEnter2D is not called.

How should we set this up, such that we can keep hacking away at the tree (getting OnTriggerEnter2D calls) without moving the character, only enabling and disabling a trigger Collider?

(I'm using Unity 2021.3.16f1.)

 

I've attached a minimal example project, like the one described in my previous post.

1: Press E to activate the Tool's collider. Expected: trigger entered. Result: trigger not entered.
2: Press A and D to move around a bit, then press E again. Expected: trigger entered. Result: trigger entered.
3: Press E again, without moving in between. Expected: trigger entered. Result: trigger not entered.
4: Repeatedly use the check mark in the editor to enable and disable the Tool's collider. Expected: trigger entered repeatedly. Result: trigger entered repeatedly.

What needs to change about my setup to get repeated trigger entered when pressing E without moving?