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Anticheat check - which competitive games actually work on Linux? (www.gamingonlinux.com)
submitted 5 months ago by to c/linux@programming.dev
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[–] 12 points 5 months ago* (6 children)

This is definitely solvable, though. The server can only send the client location updates of players they should be able to see.

If someone tried to wall hack, they’d only see the last known location before line of sight was broken.

Giving the client that data at all is like playing Battleship side-by-side and telling the player not to look at the other board.

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  • [–] 2 points 5 months ago* (5 children)

    This is what I mean by mitigations

    You could definitely hide far players, but as soon as a player is near enough they could be seen, particularly when dealing with humans making unpredictable input, that player's model will need to be placed in the world before either of them are supposed to see each other because the game has no way of knowing what that unpredictable input might be.

    You can't have every permutation of a given player model being obscured by every possible combination of angles of scenery as distinct models in the GPU memory, so something client side will need to do that slicing, so a player's obscured origin location will need to be known by the client. This could give a player seconds of time to react depending on their opponent's strategy

    A few milliseconds is the only advantage a player needs at the top level of these games to shift the balance in a given contest. And given the prizes for some of these tournaments is multiple millions, there's definitely the motivation to go to these seemingly extreme lengths

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  • [–] 5 points 5 months ago* (last edited 5 months ago) (4 children)

    But the server is the authority on player location. It can tell if a player is visible to another because it knows their locations (as well as any obfuscations) at any given instant. It doesn’t need to know what they’re going to do next until it gets that next input from the client.

    Obviously calculating this requires more work on the server’s part, but in smaller competitive matches this is totally doable. We’re talking basic wireframe vectors.

    EDIT: Yall are really starting to convince me to make a proof of concept for this, because I'm convinced it can be done.

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  • [–] 3 points 5 months ago

    You seem to not be taking into consideration:

    • lag
    • extra information required for graphics stuff, like shadows

    The reason your client computer needs to know the opponent's location when they are still 1m on the other side of the wall, is because, within the next 100ms, you might make a jump+move action which lets you see their shadow or the tip of their weapon.

    The shadows and reflections need to be calculated on your system or the server would be doing too much work and if you find the opponent pop up where they clearly were not, 50ms ago (because the server just told you now), you won't be particularly happy either (I know I won't).

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  • [–] 2 points 5 months ago (2 children)

    Right, but as I mentioned unless you have an actual infinite number of variations of every player model (impossible, you can't store infinite variations in fixed storage), you're going to need the full player model in GPU memory and something client side will need to do the chopping with knowledge of the players origin coordinates, it's impossible to determine the shape of and position the chopped shape without sending that information to the client. Streaming graphics data from a server into even a top of the line GPU would be a prohibitive hit to game performance when milliseconds matter.

    It's not processing power that's the problem, it's the speed of light

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  • [–] 1 point 5 months ago* (1 child)

    I think you're overthinking it. You don't need to render every skin. You just need a box that's the maximum bounds for that player model. Again, we're talking really low poly wireframes.

    These bounds are standardized across every client, so the server already knows this information.

    Games already do this with hurt boxes.

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  • [–] 1 point 5 months ago* (last edited 5 months ago)

    Ah that's even more straightforward then

    So, especially with a standard box, the client would receive the coordinates of obscured player models for the centre of that box.

    If 99% of a player is obscured, a player with a wall hack would get information a non-cheating player would not, with basically no processing or mapping needed to turn that into useful information.

    Edit: FWIW I've had this exact conversation but where I was in your shoes talking to people who work in this industry, if it could be done it would be done

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