Help with Raycasting

Hey, how do I let my raycast's continue until they are outside of the collider so I can get the back-end coordinates instead? I drew this picture in paint so you know what I'm on about:

Thanks

 

Not sure if there's another method, but once you detect the raycast hit, you could send another raycast from the opposite side/direction that only hits the originally hit collider.

Untested code, but this could do it:

Code (CSharp):

1. // do the initial raycast
2. RaycastHit2D hit = Physics2D.Raycast(origin, direction, float.MaxValue, hittableLayers);
3.  
4. // if it hit something
5. if(hit.collider != null) {
6.     // add twice the distance from the starting point to the hit
7.     // which is a point on the other side of the object
8.     Vector3 newOrigin = origin + (direction * hit.distance * 2);
9.  
10.     // raycast from the back
11.     hit.collider.Raycast(newOrigin, -direction, float.MaxValue);
12. }

Depending on how complex your shape its, this may not give the true internal collision result you're looking for, but for convex shapes this should be able to do it.