What you could do is add a wall entity to where you want the player to be able to look through, and then add an invisible wall segment directly over that. Then when they press a specific button, the real wall entity disappears, allowing them to see but not go through that section. Then you stop pressing the button, and the real wall comes back.
Would take some scripting to accomplish, and you'd have to be careful about distance from adjoining walls assuming you allow all walls to be looked through, but you might be able to do this.
Also, be prepared for performance decreases as the real wall entities would have to be dynamic for this to happen.
Priest of the Church of Joe Wood
In memory of Nanee. 9/1/1993 - 5/16/2009. Rest in Peace, little girl.
