I'm sure this has been done before, but I managed to make a moving sector after talking about the effect on the Eternity discord and was given an example wad on how to do it on Eternity. I got bored yesterday and managed to reverse engineer it on GZdoom (it's a lot simpler in Eternity!).
Anyway, the fun part is that with the static portal method and having a listening sector where the polyobject/portal is located, the monsters in this moving sector can even interact with the player. Unfortunately, I learned last night that you can't rotate said static portals, so rotating the 3d train won't work unless you make it an interactive portal, which will cancel the sound interaction as well unless someone knows a workaround.
You can also seemingly have the ceiling "independent" by having the ceiling scroll with the sector, but I feel like there should be another method. Perhaps unhinging the ceiling somehow?
Lastly, AO has to be disabled unless you want to see some minor glitches.
Now if we got to see a moving bridge similar to Heartland MAP05 that would be killer.
Tip: Press use in the 3d sector to move with the sector.
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