Portals?

In the compile step of making a map, there is this one process called "portal flow" or something. The map is relatively small and not complicated, but the last time I compiled the map, it took far longer than it should have, and it said that the map had over 1000 portal clusters and over 4000 portals total. What are portals and how do I cut down on them?

If its what happened with my first map, which i'm not 100% sure on.  This will be the biggest help by far, read it all and try to understand it.  Optimization is a must for TF2. 

What applies to you (all apply but for this question), is the visleaf page.  Those blue lines separating the rooms are the portals.  Each portal has to calculate if it can see every other portal, either from itself or through another portal.  So whats happening is, you have 4000+ portals total.  This process checks if each portal can see every other portal in the game.  Thats why adding 100 more portals and it takes up alot more time because it has to check against all other portal already there.  To reduce the number of portals, on the view selector on the right of the screen.  Click off Entities, World Details and Displacements.  This is how the engine sees the game when it renders vision.  If you see small openings going to a room that you have no plan for people to go into, then close that with either a no-draw or something else.  That small 1-2 unit wide gap is makign the engine try to render if that area behind that crack can see any other area.

I had a huge problem with this,  i used displacement columns in my map and didnt cover up the area behind them (because it blocked player vision not engine vision).  It was also a large map, rendering the visleafs took 16+ hours and i had to render quickly everytime.  To correct this i had to lengthen the wall behind my columns, i had about 50 of these so with both sides of the map i had 100 more areas that i shouldnt have and any other areas behind those first ones.

http://www.teamfortress2fort.com/forums/t/hammercompiletakeslooong-20110.aspx


This more than likely answers the question.

Basically, you probably have LOTS of small, intricate pieces of geometry that should be set to func_detail so that portals do not need to be created around them.