Because there shouldn’t be any “obstacles” behind the portals. I do not know the tech behind it, but even Ondrej said there is no way to be 100% sure if portal will speed things up or not, you just have to try it. And comparing different configurations is not very time-consuming. You can select a region, or render only a few passes. Placing the portal in the door frame would be pretty much like in this example, only more extreme:
Thank you for your quick reply. You’re that best mod i’ve ever seen
I’ve read the article. but i still don’t understand why he said he place a large portal at the top of building.
If i dont mistake, the portal supposed to place at the hole (with perfectly capping).
Oh, sorry, I did not notice you are not OP. There was a big “window” at the top of this building. I probably can’t share the file. There was something like an “atrium” in that building, and light was coming through the top, and then bouncing everywhere, also into that room through the door. It made more sense to place portal in the top opening, than in the door.