How can I detect which SIDE of a box I collided with?

Question

INFO.... I am using an empty with 4 cubes (That have Ridgedbodys & Box colliders and using the "function OntriggerEnter") to make up my gameobject "BLOCk". My BLOCK will be my player and drop to the floor(A Plane) slowly, if it hits the floor or the top of another BLOCK it will kill the movement script and create another BLOCK to control at the top.

Question.... I want to DoSomething if I hit the "TOP" of a different BLOCK but DoSomething else if I hit the "SIDE" of that BLOCK.

I would like to keep it simple and not use a char controller, but from what I am reading that might not be an option. I was thinking of using a raycast maybe.

I am using this right now for my floor detection.

 // When collides with something
 function OnTriggerEnter(other : Collider)
 {
     // gets the BlockS Object
     var block = gameObject.Find("BlockS");
     // Gets the movement script on the blocks object
     var movementscript = block.GetComponent(BlockMovement);
     
     // if the block collides with the floor
     if( other.gameObject.tag == "WallFloor")
     {
         movementscript.enabled = false;        
     }

Answer 1

umm collision detection doesnt really work if your going to transform move stuff.

If you need collision detection you need a rigidbody, you normally move rigidbodies with physics. If your moving them with transform move you should mark as is kinematic. That means it will not be moved by physics but by transform.

A kinematic rigidbody which you want to move should be done during FixedUpdate to apply collisions properly.

if you would like to know which side you hit you may raycast to the object

this code snippet shows a raycast you could perform on collision.

 //this ray will generate a vector which points from the center of 
 //the falling object TO object hit. You subtract where you want to go from where you are
  
 Ray MyRay = ObjectHit.position - ObjectFalling.position;
 
 //this will declare a variable which will store information about the object hit
 raycasthit MyRayHit; 
 
 //this is the actual raycast
 raycast(MyRay, out MyRayHit);
 
 //this will get the normal of the point hit, if you dont understand what a normal is 
 //wikipedia is your friend, its a simple idea, its a line which is tangent to a plane
 
 vector3 MyNormal = MyRayHit.normal;
 
 //this will convert that normal from being relative to global axis to relative to an
 //objects local axis
 
 MyNormal = MyRayHit.transform.transformdirection(MyNormal);
 
 //this next line will compare the normal hit to the normals of each plane to find the 
 //side hit
 
 if(MyNormal == MyRayHit.transform.up)
 {
 you hit the top plane, act accordingly
 }
 //important note the use of the '-' sign this inverts the direction, -up == down. Down doesn't exist as a stored direction, you invert up to get it. 
 
 if(MyNormal == -MyRayHit.transform.up)
 {
 you hit the bottom plane act accordingly
 }
 if(MyNormal == MyRayHit.transform.right)
 {
 hit right
 }
 //note the '-' sign converting right to left
 if(MyNormal == -MyRayHit.transform.right)
 {
 hit left
 }

compare mynormal to transform.forward and -transform.forward for the front and back plane.