Return01

This is a classic PWAD that is known only to work with early versions of the Doom engine ( <1.4 ?). Has anyone ever played E1M2 of this level on an early version of Doom and knows how it is supposed to work? I would add support to PrBoom to enable it to be played in the right compatibility mode, but I don't know how the final bridge is meant to work.

(The actual mechanics seem to be that the final bridge is a raise-to-next-highest-floor linedef, but there is only one surrounding sector and it's not higher that the sector that would form the bridge. Either early versions of doom had the floor raise indefinitely, or the line was redefined by id at v1.4, from something like raise-by-512; at least those are my best guesses.)

Never_Again recorded demos on this map as part of his two demo packs for the wad. He used version 1.4 for this particular map because of this issue. Edit: correction - actually he used version 1.2 for his first pack, and used version 1.4 for the second pack, since he had found that this behaviour was still supported in that version.

See his comments in the text-files.

Never_Again doesn't generally frequent these forums, but I have been in e-mail contact with him recently (via the address given in his text-files), so you could try contacting him directly if you need more information.


BTW, regarding 1.2 support, Gokuma provides some information here (linked to from this page) about some of the quirks of that version, et al.

I tried it in v1.4, v1.5 and v1.2 and its very weird, because if I waited below in the lava for it to rise, it would rise to the right height, but if I teleported to the catwalk above it would continue rising to the ceiling. On one occasion I even teleported to where the red key is and it kept rising indefinitely. I doubt it works different in these three versions, and id probably got rid of it because of the weird quirks.

For this map, it's supposed to rise slowly to the level of the exit ledge, which is slightly above the catwalk.

I've seen a couple of other WADs that I think have this flaw, too, such as damned, where sector 118 is supposed to rise (I guess) 256 units, but is surrounded by a sector of the same floor height and so does not rise at all.

I haven't tested that map with early Doom versions, but the text file says it has no bugs, and it obviously doesn't work as intended in 1.9, so...

Considering the experiences with Return01 (which for me 11 years ago were exactly the same as Myk had) I'd say that everyone claiming the map has no bugs hasn't tested it sufficiently. Apparently there never was a way to produce consistent results.

Maybe the best solution here is to fix the map and re-upload it to the archive. In its current state it's practically useless...

Graf Zahl said:

Maybe the best solution here is to fix the map and re-upload it to the archive. In its current state it's practically useless...

It is useful:
People recorded demos with it.
That makes it a great benchmark for source ports, that try to emulate vanilla as close as possible:
Chocolate-doom, prboom, prboom+ ...

Greetings
Funduke

Graf Zahl said:
Considering the experiences with Return01 (which for me 11 years ago were exactly the same as Myk had)... Apparently there never was a way to produce consistent results.

After more investigation, I tend to agree. Looking at the Heretic source, which forked pre-Doom 1.4, we can see the actual bug: if there are no higher sectors for a raise-to-higher sector to target, then it uses whatever random/junk value happens to be in heightlist[0] on the stack. So there's no reliable way to support it.

In practice, the target height the level wants is 0 - and there is a good chance of finding a number 0 or close to 0 on the stack, I guess, which is probably why it often works. So I will have doom_12_compatibility assume a target height of 0. If I'm lucky, this is the only level that ever uses it, and so 0 is the only right answer it needs.

Thanks for the helpful replies.