I was thinking, since CSG and BSP compile before VIS and RAD, it would be possible to feed VIS "fake" data from an altered version of the map you're making.

Get a load of brushes to obstruct the view around a corner/etc, for your map (we'll use a texture called "FAKE" or something here). Now export your map, run all compilers, it should produce a BSP if all goes well.

Now back up your mapnames.PRT file, we'll need that in a bit.

Now go back to hammer, delete all those FAKE textured brushes, and export the map again.

Now run only CSG and BSP; then return the mapnames.PRT file you backed up to the directory where you do all your compiling.

Now run VIS and RAD.

It's experimental folks! You may find things like "not being able to see things", depending on how you lay out your FAKE brushes.

I dont understand how this is ment to be useful?

You'll need to understand about VIS to understand this.

I'll put up an example map when I get the time!

I think you can get the same effect by using hintbrushes but it is an intresting idea. :)

Have you tried it? Does it work or does the compiler crash? My guess would be that there is somekind of index for the portals and leafs which mess things up pretty bad...

yeah, its similar to hint brushes, but when used with hint brushes, r_Speeds could be seriously cleaned up.