BoxCollider2D, problem with corner

Here's a simple example of how to do that. Add it to a GameObject that has a BoxCollider2D on it and it'll calculate and draw the points of the corners. The part you actually want is in the "Update" method which simply takes the collider offset and half-size extents for the box then calculates each corner point in local-space. With this you can then transforms those local-space points into world-space using the Transform.

Code (CSharp):

1. using UnityEngine;
2.  
3. [ExecuteInEditMode]
4. public class FindBoxCorners : MonoBehaviour
5. {
6.     BoxCollider2D m_BoxCollider;
7.     Vector2[] m_BoxPoints = new Vector2[4];
8.  
9.     void Start()
10.     {
11.         m_BoxCollider = GetComponent<BoxCollider2D>();    
12.     }
13.  
14.     void Update()
15.     {    
16.         var offset = m_BoxCollider.offset;
17.         var halfSize = m_BoxCollider.size * 0.5f;
18.  
19.         m_BoxPoints[0] = transform.TransformPoint(offset - halfSize);
20.         m_BoxPoints[1] = transform.TransformPoint(offset + new Vector2(halfSize.x, -halfSize.y));
21.         m_BoxPoints[2] = transform.TransformPoint(offset + halfSize);
22.         m_BoxPoints[3] = transform.TransformPoint(offset + new Vector2(-halfSize.x, halfSize.y));    
23.     }
24.  
25.     private void OnDrawGizmosSelected()
26.     {
27.         var oldColor = Gizmos.color;
28.         Gizmos.color = Color.cyan;
29.  
30.         for (var i = 0; i < m_BoxPoints.Length; ++i)
31.             Gizmos.DrawSphere(m_BoxPoints[i], 0.1f);
32.  
33.         Gizmos.color = oldColor;
34.     }
35. }
36.