I don't quite see what you are going after with your window portaling. If something is transparent, you need to see what's behind it. A transparent structural (portaled) window will cause a HOM effect if the map isn't otherwise leaking to what's behind the window. Of course if you have a window hole in a wall, chances are it actually does possess a portal, even two of them if there's a whole leaf node inside the window hole, but they don't matter much unless you are farther away from either of the rooms surrounding the window.
A portal is nothing but a leaf node's face. That is, the 2D element between two leaf nodes. Areaportals and such are special cases that affect the VIS in game in a special way that's more complicated than just having a normal portal somewhere. You could have a hundred portals in a long empty corridor but still see through all of them all the way to the other end. The game draws everything inside all the leaf nodes the current leaf node's portals have a line of sight to. An areaportal has the power to conditionally sever that mechanism - you could say by severing the los as it happens in practice.
VIS fast is something you shouldn't be using if you care about the optimization of your map's VIS. If you have VIS problems, try to solve or compromise those problems on case by case basis, not by compromising the whole VIS process.
Edit: Well, even though I don't understand your window portal problem, you might want to study Antiportals. Maybe they will suit you.
[COLOR=Navy]Okay, thanks, I'll leave the windowed rooms :) But in the printed map if I save with -vis, not -vis -fast, then it's more hours...but I structuraled the outside walls, and detailed everything in it. So I don't understand why it is, and I can't save -vis, only -vis -fast:([/COLOR]
Based on that earlier screenshot of yours, the architecture or some glitch generate a high number of degenerate leaf nodes all over the place. Generating those is what takes the lenghty time you are observing. Vis fast only does very poor job of VIS, which explains why it seems to take a reasonable time even with your broken map. However, it might not be much better than no VIS at all. Although I have never used it so I wouldn't know. I only know what the manual says.
You gotta sort out your map's VIS problem. That's the only real solution.
[COLOR=Navy]Yeah, so I opened this thread...because I can't solve the problem :P Btw thanks for your replies;) [/COLOR]
Well, I'm not any VIS guru myself. I've studied enough of it to know how to use hints (and how not) and then experimented a bit to try to solve my own VIS problems caused by a skybox enveloping much of the map (a situation best avoided if possible). Based on what I can deduce with my average knowledge, there must be some fundamental or systematic error (or bad habit) in your map itself producing the problem.
I didn't make it!
What exactly is a degenerate leaf node. or a leaf node for that matter? I may have learned about it before, but if I did, I've forgotten.
Well, I just called a degenerate leaf node a leaf node that serves no purpose whatsoever. They are naturally created plentifully enough in a map having only structural brushes, for example.
A leaf node is a basic VIS unit. It could be a whole room if the room is of the simplest box type with structural walls and no structural details inside. Like I said in my earlier post, the VIS is based on tracing what other leaf nodes are visible from the current leaf node. Only the stuff in those visible leaf nodes is drawn by the game. However, if you have useless leaf nodes all over the place (like a simple box room having dozens of them even though you can see everything in the room all the time), the VIS compile will take ages and it might affect the in game performance as well.