No 3D floors at all. It's simple but clever usage of sky textures:
http://img163.imageshack.us/img163/458/skywin1.png

[EDIT]: I just tested it in software, and it gives some HOMs, but it could be easily avoided. Firstly, I tried to make the dummy-sky sectors sloped, and I got partial success... I don't have time to play around with it right now, but I'll experiment further when I get home from school.
Another way to avoid this would be a simple script that checks if anyone is using software rendering, and lowers all the dummy sky sectors to the lowest one, therefore getting rid of any possible HOMs, but it will look a bit uglier.

Considering that this is for GZDoom only, no one will play this in software as 3d floors will disappear then.

Hmm. I didn't know this was GZDoom only. No worries, then! :)

Yeah, 3d floors are cleaner than vanilla-style sky sector usage. You'll be able to stack them on each other, and so on.

I've been screwing around with a few maps lately, and for the sake of experimentation, I took a stab at making a hellish scene in Heretic:


Might be interesting for anyone wanting to make an E3/E5 map.
Also, a barrel of cookies to whoever can tell me what map this actually is. :P

Certainly interesting :)

Isn't that from Demon eclipse,
P.S. Where can I download Demon Eclipse

For the record, BlazingPhoenix managed to identify it on IRC -- it's the outdoor secret area of E1M3, or more specifically, the "evil mirror world" version of it as part of an extensive secret area I added. Try flipping the first screenshot horizontally and the resemblance will hit you. :P

I decided to give the same treatment to a couple of E4 maps ("Sepulcher" and "Shattered Bridge," namely), and they turned out not so bad. Just simple retextures this time around, but it's amazing how much a new paint job can change the look and feel of a map.




No new sectors were added in the process of making these save for the new scene at E4M4's entrance. Not bad for not adding detail, eh?

Nice looking screenshots, and a nifty idea behind it :)

We should base the final boss of episode 5 on this:

http://www.youtube.com/watch?v=V8Ca_edg6RE