Revenge of jittery movement

[Professor Frink]

The 1.9.4 patch text claims "Fixed a bug that could cause players to appear to be porting around in a small area."

I hadn't seen such a thing in 1.9.3 or previous (short of the horrible disabled client prediction in 1.9)... but now in the battlegrounds I can't help but notice some rogues popping around me in a roughly circular pattern, rather than running from place to place. I'll have to assume the patch text is a typo and they meant to say "created a bug ..."

Has anyone else seen this? Does anyone know what conditions cause it? Have a number of characters on my server's horde team simply started using a timing cheat?

-- frink

[Quark]

Has anyone else seen this? Does anyone know what conditions cause it?  Have a number of characters on my server's horde team simply started using a timing cheat?
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I've seen it once post-patch. Pre-patch, I saw it more often, particularly with players from Australia (the most often offending case is duels). Most of the times, it is a lag-induced affect that neither player can prevent.

Every once in a while, you will see someone that is cheating, unfortunately.

[Watto44]

I've seen it once post-patch.  Pre-patch, I saw it more often, particularly with players from Australia (the most often offending case is duels).  Most of the times, it is a lag-induced affect that neither player can prevent.

Every once in a while, you will see someone that is cheating, unfortunately.
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Being from Australia, I saw this A LOT pre-patch. (And by a lot, I mean just about every single player was porting.) All I've seen post patch is "normal" lag jumping, usually from rogues who are sprinting. The only way I've found to "fix" this problem is to apply some sort of snare to the player who is lag jumping. This seems to re-synch them, although it's a bit annoying being forced to burn a precious snare. :angry: (Considering that druid rogue fights are pretty much a snare/stun fight, this can be pretty frustraiting.)

Interestingly, an alliance priest tried to use his own port hack post 1.9, hoping it would be hidden by the "legitimate" lag jumping. Fortunately he was so incredibly (and stupidly) obvious about it that our entire team reported him and he hasn't been seen since. :)

While I don't know the tech reasons behind this, I would imagine it was introduced as part of blizzards effort to optimize the rendering/animation code to increase frame rates.

[kershner]

I can 'cause' this type of jumping around due to the way that the client and server interact with each other. Both attempt to predict what result a given set of actions will have.

As an example, there has been significant discussion on the forums as to whether the global cooldown is 1sec or 1.5secs. The best answer is 'yes'. The global coolddown is 1.5sec, but the amount of allowable difference between server and client appears to be 0.5sec. As such when you cast as rapidly as you can you will occasionally see the spell fail after it has successfully cast because you have been gaining time with each cast (casting a 2.5sec spell in 2.4sec for example) until you exceed the 0.5sec limit.

You can 'jump around' simply by having a bad clock chip. My roommate has a clock chip that runs a little fast and gets worse the longer his computer has been up since a reboot. (Odd yes, but true). If you leave his computer up for a few days and play WoW, I (on my machine), when running beside him will witness him running faster than myself and occasionally doing so without traversing the intervening space.

On his client he is running a little fast, because his clock chip is running fast, but he can't tell because he has no room for comparison. For the purposes of movement, similar to spell casting, the server allows some leeway on position and grants the 'benefit of the doubt' per se to the client. As such, on the server he is running a little fast, but not enough to red flag him as a cheater (because he's not), but still enough to gain advantage. I estimate it at around 10% when it is at it's worst and 5% much of the time. On my client I see him jumping about because my client predicts his location (which is what I see) and yet the server keeps informing me that he is elsewhere.

A humorous negative side effect is that all spell cooldowns are messed up for him. As spells are granted less leeway than movement, when he clicks on a spell with a long cooldown (30sec-ish) right after the cooldown has expired, the spell will often cast and then fail as he was outside the 0.5sec range. This is especially bad on his Fire Mage with Pyroblast. Imagine waiting a minute for the cooldown then casting a 6sec cast only to have the message 'Spell not ready' pop up at the end because you started 0.6 sec early.

For a true lesson in how bad the interaction between the server and the client really is, and for a shock to the senses on how successful Blizzard has been at allowing the user to not realize that things are not where they appear to be, try this experiment:

1. Get two copies of WoW running on two computers for which the monitors are next to each other.

2. Play WoW on each and run around and kill stuff together.

3. Look at the other person's screen and see where they think you are.

4. Magnify the effect by having one player Mind Vision the other and watch the same set of actions through two different clients.

-kersh

Dehmien | 60 Undead Priest | Stonemaul