Getting bounds of a prefab with multiple children

Questions & Answers
1

I have a bunch of prefabs as children of an empty game object, is there an easy way of determining what the total bounds of that grouped prefab is?

4

i wrote script that may help.

using UnityEngine;
using System.Collections;

[ExecuteInEditMode]
public class PrefabAABB : MonoBehaviour
{
    /// <summary>
    /// local space Axis Aligned Bounding Box
    /// </summary>
    public Bounds bounds;
    Transform _transform;

    void OnDrawGizmos()
    {
        Gizmos.DrawWireCube(transform.position + bounds.center, bounds.size);
    }

    void Reset ()
    {
        RecalculateBounds();
    }

    public Bounds WorldBounds ()
    {
        if (_transform == null)
            _transform = transform;

        Bounds b = bounds;
        b.center += _transform.position;

        Vector3 size = b.size;
        Vector3 tsize = _transform.lossyScale;
        size.x *= tsize.x;
        size.y *= tsize.y;
        size.z *= tsize.z;
        b.size = size;

        return b;
    }

    [ContextMenu("Recalculate Bounds")]
    public void RecalculateBounds ()
    {
        MeshFilter this_mf = GetComponent<MeshFilter>();
        if (this_mf == null)
        {
            bounds = new Bounds(Vector3.zero, Vector3.zero);
        }
        else
        {
            bounds = this_mf.sharedMesh.bounds;
        }

        MeshFilter[] mfs = GetComponentsInChildren<MeshFilter>();
        foreach (MeshFilter mf in mfs)
        {
            Vector3 pos = mf.transform.localPosition;
            Bounds child_bounds = mf.sharedMesh.bounds;
            child_bounds.center += pos;
            bounds.Encapsulate(child_bounds);
        }
    }

#if UNITY_EDITOR
    void Update()
    {
        if (Application.isPlaying) return;
        RecalculateBounds();
    }
#endif
}
3

You can construct an enclosing bounding box by instanciating Bounds and then repeatedly call Bounds.Encapsulate(bounds : Bounds) for all children to integrate their bounding boxes. See the links for details.

2

bounds as a square or as sphere?

search gameobjects in prefab, compare them all to find the one most at right, left, up down, fwds and backwards, that will give you a bounding box, or compare distance of all of them between each other, and keep the largest distance, use arrays.