Dunka,
You might be interested in this E-mail that JonoF wrote me on June 21, 2000 (Exactly 1 day after I released the Build source code!):
Build source! I can't believe it! Build source! Build source!
...
Did you have any room-over-room code implemented by yourself? I know you've said that the SW and Blood teams both did it different ways (and quite different for that matter). Just wondering whether you decided to try it yourself. I didn't seem to find any code that suggested it.
He is correct on all accounts. KenBuild does not support room over room as I never tried it myself. I did, however, fix a few things in the engine to make sure the rendering part would work for the other games.
It is certainly possible to add this capability to KenBuild or Duke. It's really just a matter of development time. The rendering portion is similar in complexity to the mirror code, so I don't expect much difficulty in implementing this. The part that most people don't realize is that you also need to hack all of the physics functions in the Build Engine (such as hitscan, clipmove, getzrange, etc...) to work with it too.