Semi-wallhack with existing cvars

[M_]

I'm not going to post the code here (yet), but it has come to my attention that there is a semi-wallhack in Nexuiz with the existing cvars. The effect is that if you see any part of a person, the entire person becomes visible (in a bright blue, nonetheless), and remains visible for a moment or two after ducking behind a wall. I played with this for a bit last night, and it made enemies too easy to track. This is a cheat. If the proper developer will contact me on irc, I can give you the code.

This came up a few days ago on irc, and the ppl involved then defended the codes as developer tools that need to stay in the game. That being understood, I can play with nearly full fps and see my enemies better than they see me.

Video:
http://www.youtube.com/watch?v=Tq4AUmhKAYk&fmt=8

This was just a quick shot from a demo where you can see the enemy behind a wall in a couple of spots.

http://www.youtube.com/watch?v=RG19vjnRc_8&fmt=8

This is a bit from last night. You can clearly see that the improvement in vision is significant.

I can easily post more video of this, or I can discuss this on irc. I am not a developer, so I don't know how much these features are used, and I don't know how easily they could be disabled for gameplay (or in a server).

[LordHavoc]

I'm not going to post the code here (yet), but it has come to my attention that there is a semi-wallhack in Nexuiz with the existing cvars. The effect is that if you see any part of a person, the entire person becomes visible (in a bright blue, nonetheless), and remains visible for a moment or two after ducking behind a wall.

There are no plans to disable these features whether online or offline, and such wallhacks have very limited cheating potential.

A quick checklist of what does and does not work in Nexuiz with wallhacks (whether using engine features or external driver hacks) when compared to other games, sorted by harm done:

Seeing an enemy before they come around a corner so you can fire at them early:
Nexuiz - No.
Other games - Yes.

Seeing a flag carrier behind a wall:
Nexuiz - No (unless they have a powerup - due to networking treating light sources as larger objects).
Other games - Yes.

Seeing an enemy after they hide so you can know if they stopped just behind the wall and might be hit by splash damage:
Nexuiz - Yes, briefly. (cvars: sv_cullentities_trace_delay_players sv_cullentities_trace_samples_players)
Other games - Yes.

Completely seeing an enemy that is only partially exposed:
Nexuiz - Yes.
Other games - Yes.

Overall I consider Nexuiz to be very wallhack resistant, it is tailored to prevent actual harm to the gameplay rather than obsession with precisely hiding entities (which increases server load the tighter the tolerances are made).

[divVerent]

I, being one of the main developers, know which two cvars you have set to which values for this.

Basically, as LordHavoc already said, the impact of such a wallhack is reduced very much by the server code (using the cvars he mentioned), and can be reduced even more at the expense of server load or display accuracy. As CPUs get faster and compilers optimize better, we tend to increase that option by a notch (just like it'll increase in the 2.5 release, showing enemies that way for a shorter time).

The option is a debugging tool that modelers can use if they wonder why lighting of their model is wrong, or that mappers can use to see how well "vis" is done on their map.

However, stopping to defend the feature, think about removing it:

If we remove it, people who want to cheat can simply put it back in in their engine, or even just use an older one. No big deal, the code for this is really simple.

And if they don't do that, there is software for Windows that basically does the same by intercepting rendering commands.

So we would gain nothing by removing this from the engine. On the other hand, if someone is suspected using a wallhack, the easiest way to prove it is to watch him with a wallhack enabled. If you see him repeatedly track enemies behind walls, you know he's using a wallhack, and I bet most wallhackers easily give away themselves that way. So the same feature that is a wallhack is also a good, or even the one true, way to prove someone is using some wallhack.

Of course, this can be checked by spectating, or using a server side recorded demo, too, so if someone is accused for wallhacking, the accusation can be verified without him noticing (so he'd turn his wallhack off). Servers can record demos of everyone without him knowing, and these demos work just fine to analyze for aimbots or wallhacks.

So if I had recorded your second video as demo file, I could have easily proven you were using a wallhack. And in "serious" matches, demo recording is mandatory for this specific reason (that is, to detect cheats if in doubt).

There is one point in the video where you maybe see too much. Some mapper should check aggressor if anything that should be a vis blocking brush is accidentally marked as a detail brush.

In the other cases, all you got was the hiding delay, which is required to reduce flickering. That delay has been reduced from 1 second to 0.2 seconds in svn (and the next release), rendering this wallhack MUCH less effective.

[shaggy]

But would this mean a DQ for the player (in a serious match). I'd assume it wouldn't be because it's a command in nexuiz, it's not a hack/modification of the engine..

[divVerent]

Yes, using this feature would warrant a disqualification, even though it does not gain much.

You detect it the usual way with wallhacks: you play back the demo with a wallhack enabled on your side. If he tracks enemies that are already behind walls, he must have had a wallhack.

Note that the wallhack works when seeing through patches or through detail brushes. Only structural brushes block the view there. Mappers should have this in mind when making their detail brushes.

[Alien]

It was mentioned several times in q3rad manual about patches and non-solid brushed not blocking the view. Probably nobody reads them anyway.