#574 trapped chests disappear if ball lightning is triggered

None
analyzed
nobody
server (359)
5
2014-04-13
2008-06-05
No

I discovered this bug on metalforge (1.x branch) but buzzsaw confirmed that it also happens with the current SVN trunk.

Steps to reproduce the bug:
- Go in some place that has large chests with many traps so that you have a chance to have ball lightning among the traps (or create such a chest yourself). Suggested locations: third part of the underwater dungeon, or random dungeons of Valriel and Gorokh.
- Create an earth wall on top of the chest so that other traps do not destroy the chest in case they are triggered.
- Try to disarm the traps. (It helps to do that with a high-level character that does not fear the failures, but is not too good at disarming.)
- If you trigger a ball lightning, then the chest disappears instantly.

According to my tests, this always happens with that trap (ball lightning) and never with any other trap. The chest, its contents and all remaining traps disappear.

Discussion

  • AnMaster

    AnMaster - 2008-06-10

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    I'm unable to see why/how this is exploitable (and thus marked private)? Apart from that, I think it may be intentional, but I'm not sure.

     
  • Raphaël Quinet

    Raphaël Quinet - 2008-06-20

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    This bug was made private because some players did not want a public discussion of the trick consisting in creating earth walls on top of trapped chests. I don't really care about that, so feel free to clear the private flag if you think that it is appropriate.

    It is unlikely that the behavior of that trap is intentional because it only happens if an earth wall is present. If there is no wall on top of the chest, then triggering the ball lighting may or may not burn the chest and some of its contents, but at least it will not disappear instantly without any message about it. Also, some of the items contained in the chest will survive. But if the chest is under a wall, then everything disappears silently when the ball lightning is triggered.

    Even if it is not intentional, we could consider this as a feature to discourage the usage of earth walls on top of chests. But in that case, there should be a message informing the player that the chest has disappeared with the ball. So either way, something has to be fixed...

     
  • Raphaël Quinet

    Raphaël Quinet - 2008-07-01

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    Interestingly, it looks like the chest does not disappear instantly, but just a little bit after the trap has been triggered. Here is a copy of the messages that I saw on Metalforge when I was disarming a chest containing more than 100 traps (the ball lightning came around the 10th position):

    [...]
    You successfully disarm the spikes!
    You fail to disarm the diseased needle.
    In fact, you set it off!
    You are pricked by a needle!

    You fail to disarm the Rune of Ball Lightning.
    In fact, you set it off!
    You detonate a Rune of Ball Lightning

    You successfully disarm the Rune of Icestorm!
    You fail to disarm the Rune of Burning Hands.
    You fail to disarm the Rune of Burning Hands.
    You successfully disarm the Rune of Burning Hands!
    You successfully disarm the spikes!
    You successfully disarm the Rune of Confusion!
    You successfully disarm the Rune of Confusion!
    You fail to disarm the diseased needle.
    In fact, you set it off!
    You are pricked by a needle!

    You successfully disarm the Rune of Confusion!

    After that, there should have been 80-90 other traps, but they were all gone, together with the chest.

    What is a bit unusual here is that 7 traps survived briefly after the ball lightning was triggered. This took only a fraction of a second because I had many "use_skill disarm" commands queued, but still this means that the chest (or at least some of its traps) did not really disappear instantly.

     
  • AnMaster

    AnMaster - 2008-07-03

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    I think this explains what is going on:
    1) Ball lightning can burn items on the floor (and are designed to do so I think?).
    2) With the earth wall on top the ball lightning can't move to another square, it is trapped.
    3) Thus it will burn items on the same square (the chest)

    What I don't get is why it doesn't beat down the earth wall, the ball lightning spell does that doesn't it? Or is it just divine shock that does? I'm not on a computer where I can check that currently.

     
  • Andreas Kirschbaum

    What actually happens is:
    1) Ball lightning does NOT burn items on the floor UNLESS there is a living object on its square.
    2) When the ball lightning trap triggers, the ball lightning is put into the chest's square. It ignores that the tile is blocked by the earthwall.
    3) The ball lightning gets a move, detects a living object on its tile, therefore hits this tile. (Earthwalls are considered living objects.) Therefore it hits the chest which then might get destroyed. Earthwalls are "resist_lightning 100", so they are not affected.
    4) If a chest is destroyed, the contained traps go off and the contained items are dropped on the ground. Most traps do not go off because the tile is blocked (by the earthwall). Similarly, the objects are discarded since the tile is blocked.

    That said, I think the simplest fix would be to disallow earthwalls atop items (including chests). While this would prevent the disarming-trick, it would be consistent in that you cannot put items below/into existing earthwalls.

    Another fix/change should be that ball lightnings should always hit the ground, not just when hitting a living object. Possibly with reduced damage in non-living tiles; would need some play-testing to be sure. The same holds for magic missiles: these also hit the ground only if a living object is present.

     
  • Kevin Zheng

    Kevin Zheng - 2014-01-21
    • status: open --> analyzed
    • private: Yes --> No
    • Group: --> 1.x_trunk
     

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