Hello, I have created a brush with func_areaportal and assigned the texture to the whole brush. The brush itself is the size of the door and aligned with the wall. The problem is that I can see the void from the inside of spawn, however once I get close to the door and it opens the problem isn't there anymore. (the areaportal is linked with the door and is closed by default). But from the outside it seems to work how it should. What do I need to do to fix the void issue, image examples below (i used r_drawothermodels 2 to show that it does hide the props behind it):
When an areaportal is closed (and there are none other open ones) so that two areas can't see each other, the engine will not draw the other area. That's the "area" part of the name, As such, you should only close areaportals when the player can't see into it. Such as when there is a door in the way. Your problem is that the specific door prop you use isn't suitable for hiding a closed areaportal.
There are 3 doors on each side of the map for the spawns like in the last image. The area portal is tied to that door and is set to closed state as the door by default is closed. Valve maps have the area portal in the doorway and set to open at the start so I will see what that is about.
It looks like you're having the same problem I did yesterday. You need to make the Areaportal 1 unit wide and position it inside the sliding door prop. What's happening right now is that the Areaportal is hiding the area behind it, including the door. It needs to be inside the door so that the door hides the culling.