Changing BoxCollider2D size to match sprite bounds at runtime

I have an object that's pooled which I recycle. When I recycle it and add it to the game, I sometimes change its sprite. The problem is, the BoxCollider2D I have attached to it stays the same size. I would like to make its size match the bounds of the sprite, like what happens if I just create a brand new game object in the editor, plop a sprite on it, and then plop a BoxCollider2D on top of that.

My issue is that I don't quite know what the numbers mean in regards to Box Collider's size field. The docs say it's the width/height of the rectangle, but I'm not sure in what units. My sprite certainly isn't 1.74x0.31 pixels in dimension. So I assume it's a scale of some kind. Anyway, my question is: how do I compute the values to put in this size field such that it matches the bounds of the sprite, at run time? Thanks.

 

Truth be told I don't know either, BUT I know a workaround.

Code (CSharp):

1. Vector2 S = gameObject.GetComponent<SpriteRenderer>().sprite.bounds.size;
2.         gameObject.GetComponent<BoxCollider2D>().size = S;
3.         gameObject.GetComponent<BoxCollider2D>().center = new Vector2 ((S.x / 2), 0);

I use this for melee attacks in an action platformer currently. the bounds.size vector will give you the right numbers in scale... I think. (Test this though, I have everything set to 1 pixel/unit to help fix tileset clipping problems). Set it Update() it'll match the sprite's bounds every frame, but there's a couple quirks.
1. Bounds.size measures whatever you defined the sprite as, even if there aren't any visible pixels in like half of it. If you left any blank space (say, using 'grid' to get frames out of a tileset), that's going to be in the collider too.
2. You might want to define what order scripts run in for this. If this fires off BEFORE the animation code, the collider's always going to be one frame behind the sprite. It's unnoticeable unless your framerate's really low, but something to be aware of.

 

Awesome, that worked. Thanks!

 

Also, worked for me. Thankx.

 

well my game object is constantly growing every frame how could i get my boxcollider2d to stay on it (it will also be going in odd directions)

 

Thanks for the workaround! Worked for me to too!

 

It worked for me also, thanks!

 

Here is the code i wrote for my collider to match my sprites.
the problem with Kawaburd solution is that firstly it doesn't consider the scale to the account and secondly that ".center" is deprecated and honesly modifying it in the latest unity versions is unnecessary

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. [ExecuteInEditMode]
6. public class ColliderFitSprite : MonoBehaviour
7. {
8.     void Awake()
9.     {
10.         runInEditMode = true;
11.     }
12.  
13.     void Update()
14.     {
15.         var _sprite = FindObjectOfType<SpriteRenderer>();
16.         var _collider = FindObjectOfType<BoxCollider2D>();
17.  
18.         _collider.offset = new Vector2(0, 0);
19.         _collider.size = new Vector3(_sprite.bounds.size.x / transform.lossyScale.x,
20.                                      _sprite.bounds.size.y / transform.lossyScale.y,
21.                                      _sprite.bounds.size.z / transform.lossyScale.z);
22.     }
23. }

 

it works thanks ....

 

Thanks works fine for me.
Only thing I have to change was center to offset and maintain zero in x and y.

 

This is for BoxCollider2D
Know any way to make this work for edge collider so that i can have objects IN this object

 

Code (CSharp):

1. using UnityEditor;
2. using UnityEngine;
3.  
4. [ExecuteInEditMode]
5. public class BoxCollider2DFitSpriteRenderer : MonoBehaviour
6. {
7.     [SerializeField] private Vector2 _sizeOffset;
8.     [SerializeField] private Vector2 _centerOffset;
9.     private SpriteRenderer _sprite;
10.     private BoxCollider2D _collider;
11.  
12.     private void Awake()
13.     {
14.         runInEditMode = true;
15.         _sprite = GetComponent<SpriteRenderer>();
16.         _collider = GetComponent<BoxCollider2D>();
17.     }
18.  
19.     private void Execute()
20.     {
21.         if (!_sprite.enabled || !_sprite.gameObject.activeInHierarchy) return;
22.  
23.         Vector2 scale = transform.lossyScale;
24.         Vector2 size = _sprite.bounds.size;
25.  
26.         size = new Vector2(size.x / scale.x, size.y / scale.y) + _sizeOffset;
27.  
28.         if (size != _collider.size)
29.         {
30.             _collider.size = size;
31.             #if UNITY_EDITOR
32.             EditorUtility.SetDirty(_collider);
33.             #endif
34.         }
35.  
36.         Vector2 offset = (Vector2) (_sprite.bounds.center - transform.position) + _centerOffset;
37.  
38.         if (offset != _collider.offset)
39.         {
40.             _collider.offset = offset;
41.             #if UNITY_EDITOR
42.             EditorUtility.SetDirty(_collider);
43.             #endif
44.         }
45.     }
46.  
47.     #region Editor
48.  
49.      #if UNITY_EDITOR
50.     private void Update()
51.     {
52.         if (Application.isPlaying) return;
53.  
54.         Execute();
55.     }
56.     #endif
57.  
58.   #endregion
59. }
60.