I have cut out an area to use as a test and here's what it looks like in g3.3pre39-g2f45218 (which is an earlier git build that I just happen to have installed):
Outside the area before activating the green colour:
After making the area green:
Back to the green area looking out (not actually in the green area yet):
Walked backwards into the green area:
All the above screenshots are as expected.
And here's how it looks in 3.7.1
Outside the area before activating the green colour:
A bit darker, but that's just differences in setup between the two installs
After making the area green:
Pretty much as expected
Back to the green area looking out (not actually in the green area yet):
Also much as expected.
Walked backwards into the green area:
Well, that's not what it's meant to be like!
I can't check in a more recent 64 bit git build (because of the startup crash) but the 32 bit build from today still shows this behaviour.
It only seems to happen under 3D floors. Most of map113 (the previous map) gets flooded with gas and it looks fine. Even in the attached test map, if you noclip into the model sector for the 3D floor, it looks fine:
I have tried different sector lighting modes, fog modes and AO settings but none of the changes seemed to make a difference.
The attached map is the test map that I used for the screenshots. It's just a bit cut out of my Burghead map and converted to UDMF. Load it and puke script 1 to create the green.
If you want to clear the clear the green colour again, you can puke script 2. Just like in the original mod, this is meant to fade the green fog colour back to normal lighting (it's a bit clunky, but it basically works in the original mod). However, unlike in the original, as the fog fades, the light seems to get darker (to almost black) in the under-3D-floor sectors before suddenly clearing to normal lighting.
