Collision detection bug

[ZZYZX]

Don't know if someone else also found it, but I was much like my cat on picture to the left when I first did it :)

Basically, this bug allows noclipping through walls given that you have some player to assist you and there's second wall aligned like on picture (see "how to reproduce").

phpBB [video]

The [video] tag is deprecated, please use the [media] tag

How to reproduce:
[spoiler][/spoiler]


During our tests we discovered at least 4 places where this is possible on D2M1 and at least 3 places on D5M1. Also there's some chance it works in first room of both maps (the one with BFG in D2M1).

Don't think that has any use in regular competitive game modes, but it might be useful in team competitive and cooperative modes.

[Catastrophe]

So would it let you clip out of the map or just impassible lines?

[ZZYZX]

You can noclip out of the map if there's no sector behind wall you are trying to go through. See beginning of DOOM2 Map01.

[Qent]

Does wallrunning and/or plasma bump need to be enabled?

[Combinebobnt]

There is also another method of doing this with just a single person. Plasmabump needs to be on, and if you run straight forward at certain wall angle, you will eventually break through the wall and escape the map. (like that one angle in Dwango5map01) It usually happens with obtuse angles.

[Watermelon]

There is also another method of doing this with just a single person. Plasmabump needs to be on, and if you run straight forward at certain wall angle, you will eventually break through the wall and escape the map. (like that one angle in Dwango5map01) It usually happens with obtuse angles.

General question to anyone: Does this happen in vanilla doom?

[Combinebobnt]

Me and Quadrumpusguy tested the Dwango5 map01 collision bug on singleplayer, and we could not get through the wall angle on either Chocolate Doom or DOS (Vanilla) Doom. (we couldn't get chocdoom multiplayer working)

Edit 1 : Could not replicate d5m1 angle walkthru in Odamex singleplayer, with a variety of physics compatflag changes too.

Edit 2 : Could not replicate d5m1 angle walkthru in Zdaemon singleplayer, with the oldschool flags enabled and disabled.

Edit 3: me and quad tested on Odamex MULTIPLAYER, testing both the 2 player thing for the d2m1/d5m1 bfg grate, as well as the d5m1 angle again. We couldn't get either bug to work.

Edit 4: me and quad tested the 2 player collision thing on the grate >in ZDaemon multiplayer<. In a 20 min period of testing, we successfully got quad through the grate 2 times. It seemed to happen when he ran so that he got caught between my collision box and the slope, and then i moved out quickly and slightly, then began to run into him. When enough momentum built up or something, I let go and it shot him through the grate. Also throughout this testing and not getting through the grate, sometimes the player SPRITE but not collision box would go through the map for a second. Weird.

Edit 5: Unsuccessful in pulling off the 2 player grate thing in chocolate doom multiplayer

Edit 6: Unsuccessful in pulling off either in odamex again, even using the different techniques we did in the zdaemon server.

Edit 7: Unsuccessful in pulling off -either- bug in the latest zdoom or gzdoom, with the dwango5 map01 angle and by summoning doomplayer 's and using those to try and execute the grate bug.


So far:

Vanilla & Chocolate: neither
Odamex: neither
ZDaemon: grate only (very rarely)
Zdoom & GZDoom: neither
Zandronum: both bugs present


(also Hex9019 said this bug is the result of putting prboom code in to get plasma bump, not to mention that if you go on thing bridges with plasma bump in zand, you will slide like a bar of soap as friction ceases to apply.)

[ZZYZX]

Yes, some people say this bug (and also bug that allows running out of the map from some corners) exists only in Zandronum.

Edit: from your tests it looks like 2-player bug was present in ZDoom before ZDaemon unlike 1-player corner bug which doesn't work there.

Also throughout this testing and not getting through the grate, sometimes the player SPRITE but not collision box would go through the map for a second. Weird.

I guess that was famous ZDaemon clientside predicting.

[QuadrumpusGuy]

Yeah. The ZDaemon results were... interesting. I remember at one specific time it looked like Bob HAD gone through the grate, yet reappeared where I could feel the collision box after adjusting his location. In addition, there was one point where his player had appeared to go through the main entrance to the BFG, yet the Collision box remained to the left and never crossed that threshold.

The other tests were relatively the same. While move-bobbing did go berserk at times, we never successfully escaped the map or clipped through the grate.

Out of curiosity, is Compat_PlasmaBump unique to this port?

In addition, there are more maps the one-player bug can be demonstrated on - I can demonstrate if it is needed.

[Catastrophe]

Plasma bump bugs out a bunch of other shit too, like the fake 3d floors will make you accelerate really fast for no reason.

[QuadrumpusGuy]

Another note I forgot to mention:

Although the same collision bug doesn't exist in Vanilla DooM, there is another sort of bug that is similar in behavior to it in Vanilla DooM. I've found in MAP19 on DooM II that I was able to wallrun past some torches that normally should block you. I just performed a wallrun on a lower wall (wasn't a one-sided impassble linedef - might apply to it though (requires a test)?) against a torch and managed to clip past the torch.