How do you make a brick disappear when you don't look at it? I've tried look vector, but I don't really know how to use it.
Haven't done this myself, but might be able to draw a ray or raycast to do a "line of sight" test and essentially the ray will run into an object, and if it does so you can make it visible.
You might find this useful to create a Ray (from wiki)
Ray.new(Vector3 origin, Vector3 direction)