Client-server Action Synchronisation

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074 wrote:

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wakko wrote:

I'm just curious... How does Diablo 2-3 do it? I havent played Diablo 3 myself, but when I've watched Kripp play it I havent really seen any desyncs or seen him complain about desyncs. Diablo 3 is always online too (for pc atleast) right? And I have never really had any desync problems in diablo 2 that I can remember right now.

They don't try to do "predictions" like PoE. You click, you send a command, you get server saying ok, and you get results, which ensures everything happens exactly as they should. They have fast servers around the world to ensure low ping. To conclude: 1. They don't have "predictions" to mess up. 2. They have much better ping which results in immediate response of clickings.

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wakko wrote:

Then why wouldnt GGG do the same for PoE? That system sounds way better than PoE's system. Is it just a bad design choice or somehow limited to the engine or whatever?

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074 wrote:

Everyone is talking about the EFFECTS of desync. But here is the real CAUSE of the problem.

So in short, desync happens when client prediction and server prediction doesn't match up during the latency (let's say 200ms which is typical, for the sake of this exercise).

So in short, the root of all the problems is latency.

I'm not going to explain why the typical 200ms is far too long a time. In a game like this, A LOT can happen in 200ms, which is 0.2 seconds, especially when fighting large number of mobs. Hell, your attack speed often far exceeds 0.2 seconds. But the point is, 50-200ms is a horrible latency for any online game in this day and age.

Other games don't have this problem, because they have good ping. If you have played any first person shooter, you will know anything ABOVE 50ms is unacceptable. PoE has an even worse effect from poor ping, because there is a lot more things going on in an action RPG then a first person shooter. You have path-finding, multiple skills going on at the same time, range detection and hit detection of many targets. In a shooters game, it is a lot simpler, because you only have the players position, and the point you are shooting at.

Another reason is because these actions take place over a longer period of time in ARPG than FPS, so their effects compound. PoE path finding affects the whole journey of you walking from point A to point B, and if anything happens, your desync effects accumulate and stack. In an FPS it is only the immediate instant moment that is affected (you either hit or you don't).

So there is no way you can remove desync if you don't remove latency.

So now I am getting at my point.

Why the hell do you not sprinkle servers across the globe and make everyone have the best ping possible, like you would do with an FPS game? You can rent servers in every country and effectively run the game like Counter Strike or Quake Live where latency is king. This is especially more important for your game because of the reasons above you have even a greater interest in minimizing ping than pro-FPS games. You are aiming at below 10ms.

I don't understand why this is not the TOP priority of your company, because this is where your problem is. You blame everything on lightspeed, but you don't do anything to shorten this distance like what FPS games do.

Basically to solve desync, you need to rethink your attitude to your ping time (it is much more important than everything else), and you need to do it like you would with Counter Strike (sprinkle servers EVERYWHERE).

Your ping is now your king. There, REAL problem addressed. Now do something about it.

If I hear you say "50-200ms" and not "20ms" one more god damn time, I will quit and play D3.

TLDR: We counter strike now

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MortalKombat3 wrote:

Dont blame ping only. PoE desyncs far more, than it should for a given latency. Sometimes you "rubberband" after few SECONDS of desync, which means game data wasnt syncronized for SECONDS, and that's completely unacceptable.

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Chris wrote:

Suggesting we switch to a synchronous action model like RTS/MOBA games really isn't a good solution. I understand that RTSs/MOBAs don't have desync, but they do have lag after each and every click. When the semantic is that you're ordering a unit around, this lag is understandable, but if you *are* the unit, then it feels really terrible. Right now, our client-prediction allows users in obscure countries to play Path of Exile while under 200+ms of latency. This would be a much worse experience under that alternate action model. In addition, it'd require rewriting most of the game.