Bug #266

Clients are too thin (they can walk trough small holes)

Added by halfgaar over 16 years ago. Updated almost 10 years ago.

Target version:
Start date:
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When playing jDoom multiplayer, my opponent, who is
always the client, can walk through holes he wasn't
intended to walk through, he's too thin. In one map, it
even spared him getting a key. It's probably not just
jDoom related, but I can't confirm the other games.

Here is an example location (do img-tags work? If not,
just think them away :)):


The client can walk through the pillars. On the map,
it's here:


As you can see, it's map E2M4, doom ultimate.

Labels: Multiplayer


#1 Updated by carlos_ed over 16 years ago

Logged In: YES

If this is what I think it is, this problem is also
related to one I posted... about a year or so. AND STILL

It seems there is a problem in client movement prediction
code that causes clients to move through obstacles they
shouldn't be able too. Like narrow cracks in walls, to
climb instantly from a lower floor to the top of a
crate... etc.

Actualy, the client itself doesn't do that. From the
client point of view, everything is normal. But from the
server you can clearly see the predicted "ghost" of the
client to ignore certain object clipping rules. And since
it's that "ghost" that counts gamewise, this can be used
as a severe exploit to solve situations in an "cheating"

On a side note here: It pains me to see loads of progress
in certain areas of Doomsday, while these and some other
bugs still linger unchecked by the developers. My point
is, gameplay bugs should be given high priority. But it
seems emphasis is placed rather on the graphical aspect of

#2 Updated by halfgaar over 16 years ago

Logged In: YES

About that ghost problem. I noticed that too, but I
experienced it merely as an appearance issue. My co-player
often asks "hey, what are you doing down/up there", while
I'm actually standing close to a wall or near an edge. I can
see my co-player on top of walls/down cliffs as well, but
when he shoots for example, the bullets do orignate from the
proper location. At least, I believe so. You are inducing
doubts in my brain :)

As for it taking a long time to fix these issues, I have to
agree. But I can also respect people not having time. Also,
I don't like bashing the author, Jaakko Keränen has done a
terrific job in creating a modern-yet-classic doom with all
the original doom gameplay issues/bugs that people have come
to get used to as they were. I've seen older games
implemented with new engines with far less success and
original feeling/gameplay than jDoom/doomsday. I wish I
could help, but my game-programming skills are not very
good, being a web-developer (at the moment).

#3 Updated by carlos_ed over 16 years ago

Logged In: YES

Well, yes the shots originate from the correct location, I
too think so. But, if a keycard is atop of a tall pillar
you're supposed lower some other place or have to go
trough a 40 minute great map, and some noob picks that key
using that exploit and rushes to the exit, ending your 40
minute fun in about 20 seconds. How does that leave you?
lol! x)

Anyway, I'm not bashing anyone, and I really don't think
anyone has the right to do so in this case since Doomsday
is free software. But I think I DO have the right to
voice my dissapointment of having waited for more than a
year for fix for 2 exploits and seing butloads of other
improvements and those remaining there.

On a side note:

The other exploit is a game pause bug in Multiplayer. Very
easy to reproduce:

1) Create the game.
2) Have the clients join the game.
3) Pause the game
4) Have the clients leave the game and re-connect.

Result: They can roam the area free while the game is
paused. Even though they can't interact with the world,
the ability to move while the game is paused can be used
as an exploit, for example, when you create a DM game and
need to force people to wait for all players to enter the
game before the "battle royale" to start properly. :)

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