The topic of areaportals themselves, is by far too big for areaportals to be detailed, or even properly described, here. Instead, users should be directed to the new areaportal page instead, for an explanation. --Andreasen 09:27, 16 Sep 2007 (PDT)
There is alot of information on the "areaportals" page, I wish someone would have mentioned these two things on this discussion page.
1. when making an area portal the room has to be sealed so that if you poured water into the room you are trying to use the func_areaportal on it would not be able to leak that water. Each room you are sealing off must be leak proof as if it is it's own minimap.
2. Leaving the func_areaportal in it's default "open" state worked best for me. Through the reading I had done it had mislead me to think that every portal needed a trigger or a door tied to it to be most effective. After much testing "open" area portals work wonderfully.
There are some great tutorials on youtube and I feel visually you need to see it to understand it if you are new to using func_areaportal's.
func_areaportal is used to help framerate by telling your client when to and not to draw objects in the room/area you are sealing off with it.
Please read the areaportal page, it's both informative and entertaining to say the least.