So I noticed the entry on the Doom wiki says that in Doom2 map18, there are walls in the nukage pit that are the wrong texture and don't show the line of green nukage at the bottom.
This screenshot illustrates:
https://doomwiki.org/w/images/0/03/Doom ... re-bug.png
I was looking at the map in an editor and the weird thing is, those lines are the correct texture. All the lines are set to lower unpegged and without any sort of offset, yet some display correctly and some don't. What's the nature of this bug? Even if you open the map in SLADE the walls appear the way they should be, but if you open them in a Doom port, they're not aligned properly. Does anyone know what's causing this issue?
What's this bug in map18?
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Heisanevilgenius
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Enjay
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Re: What's this bug in map18?
For info, I've moved the thread because I think it's probably more of a general query than a mapping one, but there is some overlap I guess.
I just checked the original Doom2 exe - and it also displays the wall without the green edge showing. So, at least ZDoom is showing it correctly with respect to how the original game looked, and the game has always looked wrong (i.e. it's a bit of sloppy mapping - not that poor texture alignment in the original game is unusual).
I also checked in DeePsea's 3D viewer - it uses the Risen3D source port as its 3D editor, and it shows the green strip. Ultimate Doom Builder showed it the same way as the game (i.e. no green strip).
I think what is going on here is related to the heights of the sectors. The line that shows the green strip is on the lower front side of a sector that has floor 0, ceiling 192. The ones that don't show the green strip have a sector behind them that has floor 0 and ceiling 0. That's important because there is a 192 difference in ceiling height. The texture itself is 128 tall so the ceiling height difference is 64 units "out of phase" with the texture height. That's what we see in game; the texture is misaligned by 64 units in the Y direction.
(There are also other shenanigans going on in the area with a few sectors being used to lower/raise the sky to give the impression of different heights of walls around the courtyard, but they don't seem to impact how the walls in question appear.)
If you raise the ceiling height in the zero-height sector by 64 units, then the texture shows correctly. Similarly, if you lower the ceiling height in the 192-tall sector by 64, the texture alignment of the one that was correct now matches the rest (i.e. it no longer shows the green strip either). Of course, you can offset the badly displayed textures by 64 units to get them to appear correctly too.
As to why some engines and editors are showing the lines with the green strips visible, but the original game, ZDoom and Ultimate Doom Builder do not - I really don't know.
The wiki is misleading on that point. It saysHeisanevilgenius wrote: ↑Sat Nov 08, 2025 7:19 pm So I noticed the entry on the Doom wiki says that in Doom2 map18, there are walls in the nukage pit that are the wrong texture and don't show the line of green nukage at the bottom.
As you identified, no it doesn't; they just appear to be different because of how they are aligned.The pit near the start area has different textures for the lower texture.
I just checked the original Doom2 exe - and it also displays the wall without the green edge showing. So, at least ZDoom is showing it correctly with respect to how the original game looked, and the game has always looked wrong (i.e. it's a bit of sloppy mapping - not that poor texture alignment in the original game is unusual).
I also checked in DeePsea's 3D viewer - it uses the Risen3D source port as its 3D editor, and it shows the green strip. Ultimate Doom Builder showed it the same way as the game (i.e. no green strip).
I think what is going on here is related to the heights of the sectors. The line that shows the green strip is on the lower front side of a sector that has floor 0, ceiling 192. The ones that don't show the green strip have a sector behind them that has floor 0 and ceiling 0. That's important because there is a 192 difference in ceiling height. The texture itself is 128 tall so the ceiling height difference is 64 units "out of phase" with the texture height. That's what we see in game; the texture is misaligned by 64 units in the Y direction.
(There are also other shenanigans going on in the area with a few sectors being used to lower/raise the sky to give the impression of different heights of walls around the courtyard, but they don't seem to impact how the walls in question appear.)
If you raise the ceiling height in the zero-height sector by 64 units, then the texture shows correctly. Similarly, if you lower the ceiling height in the 192-tall sector by 64, the texture alignment of the one that was correct now matches the rest (i.e. it no longer shows the green strip either). Of course, you can offset the badly displayed textures by 64 units to get them to appear correctly too.
As to why some engines and editors are showing the lines with the green strips visible, but the original game, ZDoom and Ultimate Doom Builder do not - I really don't know.
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fakemai
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Re: What's this bug in map18?
The short is that you want to check the doomwiki article on texture alignment since it explains how it all fits together, generally speaking the texture rules work pretty well, but now and again you'll get forced to restructure your map. Maybe less so in UDMF, I haven't checked that out much. As for editors and other source ports, probably just a simple bug. Also while not applicable here GZDoom does modify many maps when loaded through a big database, mainly to fix bugs, even if a few of the main IWADs.