How do I get the bounds of a rigidbody's compound collider?

Physics
1

How do I get the bounds of a rigidbody’s compound collider?

I’ve looked through the Unity documentation and googled looking for the answer and couldn’t find anything about this. If I need something like that, would most people just grab the bounds from “renderer.bounds”?

Thanks!

edit: I just realized this post may be in the wrong catagory, not sure though. Should I have asked this in Unity Answers? Or the scripting forum? Whoops, sorry!

2

Loop through the children and get their bounds, and add them all together.

–Eric

3

Thanks! ‘Adding’ might not have been the most accurate word. I first tried adding all the sizes together and realized that was inflating too much (interior colliders extending length). Looking at the documentation, ‘Encapsulate’ is what I needed to do. For anyone needing to do this in the future, the code is something like:

		Collider[] myColliders = GetComponentsInChildren<Collider> ();
		Bounds myBounds = new Bounds (transform.position , Vector3.zero);
		foreach (Collider nextCollider in myColliders)
		{
			myBounds.Encapsulate (nextCollider.bounds);
		}
		Debug.Log (myBounds);

The myBounds variable is printing out nicely to the console, and changing the rotation of the parent is increasing/decreasing the size of the AABB! Woot! :slight_smile:

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4

Indeed, Bounds.Encapsulate is what I was referring to; sorry for not being more specific. Glad you found it anyway. :slight_smile:

–Eric

5

Since this answer is still valid 7 years later, I wanted to correct something:

If your colliders do not encapsulate the transform.position of your rigidbody, the solution above will not give the correct results. Here’s a utility method that works even in that case:

      public static Bounds GetCombinedBoundingBoxOfChildren(Transform root)
        {
            if (root == null)
            {
                throw new ArgumentException("The supplied transform was null");
            }

            var colliders = root.GetComponentsInChildren<Collider>();
            if (colliders.Length == 0)
            {
                throw new ArgumentException("The supplied transform " + root?.name + " does not have any children with colliders");
            }

            Bounds totalBBox = colliders[0].bounds;
            foreach (var collider in colliders)
            {
                totalBBox.Encapsulate(collider.bounds);
            }
            return totalBBox;
        }
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