if 4 objects touched the block it will be visible or unvisible

function OnCollisionEnter (collision : Collision) {

//when the block have 4 objects touching the collision…
if (collision.gameObject == 4)
renderer.enabled = true;

//the block will be visible or unvisible (rendered mesh or unrendered mesh)
else (collision.gameObject < 4)
renderer.enabled = false;

Unity won’t tell you how many different things are touching you. You have to work to count them. collision.gameObject is the thing that just now hit you. For example, a Cube. I think you may find this difficult.

The basic idea is to declare your own integer: public var touchCount : int;. It doesn’t have to be public, but that will let you see it while you run. Then the ifs will look like if(touchCount==4).

But touchCount will sit there like a lump always being zero unless you change it. OnCollisionEnter might have touchCount=touchCount+1; in it. Then, much later, subtract one in CollisionExit.