Multiplayer, replication getting past the limit of AI bots.

For testing i created very simple snail AI bot, that just randomly wanders.
Then i tried to test how many of those i can spawn on server and replicate.
The bad thing is that i can do only around 20-25 without noticeable lag. This is very bad news.

So any ideas how to put around 400 of those AI bots in level? Why 400, its because that is when my PC starts to choke with non replicated version, so i kind of want to eliminate soft cap from replication.

My first idea is to replicate only AI orders. For eg server manages all bots, gets random destination for new order, tells bot to go there.
And instead of replicating that bot movement, it replicates only event that gives order “go to [X,Y,Z]”, all snail bots on clients will got there on their own.
But before i rewrite half of AI code, did anybody try something like this? I am worried that in big crowd even slight difference to when event fired may give different outcomes, so clients will see wrong state of snail swarm.

Are ther some useful console commands to see what exactly eats up bandwith. I also suspect that this lag may be due to collision of snail to snail, or maybe navigation goes nuts with 30 of snails trying to find path. So console commands for seeing what is going on with navigation and how much collision costs would be great.

Unfortunately I haven’t played around with multiplayer yet, but I hope my input can still help you.

Have you tried a deterministic approach?
Try synchronizing a seed, assuming the numbers are generated in the same order on all clients, the destinations (and of course other things) should be the same. Of course this only works with simple AI, as soon as it reacts to stuff (e.g. player) it gets more complicated.

Many games calculate on the client and cross check/update only rarely. You could try updating only parts of your swarms (e.g. in bunches of 25).

Use Network Profiler to see what is actualy going to. And did this 400 snail thing work when you were not replicating movement, like in singplayer?

Yeah it seems strange that 20 to 25 mobs are causing you to lag. You must have something wrong there. I have seen 200+ mobs replicating basic movement without any noticeable lag.

Are you just letting the actor itself replicate its movement or are you replicating all the ai logic? Cause just the move actor should not be hitting a limit at / around 20 - 25 or so. Should be able to do way more then that.

I did some more tests on it (also redesigned my whole multiplayer setup). It is a bit better, but nowhere around 400 or so ai enemies.

I am animating all of them on server side, then using built in replication. This is what i try to change next. Ie doing them on server side then replicating only locations, so clients can place their own enemies that are not replicated. If this does not help i will place (above certain density) pack of enemies instead of single actors. But that is probably too much coding for small game feature (ie huge crowds/swarms). There was some instanced crowd support back in UDK times, this would help me for my problem. However i seen nothing like that in ue4.

I think big part of problem was collision, they were simple AI, after changing them to detour, i could go to 70 or so.
Also I am running 3 game instances on quite powerful rig (980ti skylake, i7, 32gb ram), Single instance could probably go easy to 200 or so.
But those 3 instances help me estimate how game would run on some older hardware.
There is also network saturation that plays huge role in this lag.

Have you looked at the debug stats to see how much is being sent / num of packets /ect. ?

What kind of lags are you experiencing?

With about 100 of actors (and 3 game instances running on single PC) ai actors start warping.
I know it is a lot for single PC to handle, but mine is quite good, and running those 3 instances should simulate load on something around minimal config i am aiming at.

If i run this same game 3 times without lan simulation it has low fps (20-30) but no warping.

I haven’t look into lan stats, but I think it is saturated lan connection.

I know this is an old thread, but I’m having the exact same problem. Once I have about 20+ AI characters wandering around, then their movement on the client becomes noticeably jerky. This is running separate instances of the game with just two players over a local network. I can’t believe that the underlying networking is so inefficient that it chokes on a LAN with just 20 characters doing nothing other than wandering around. There must be something wrong.

For anyone interested I created a bare minimum project to reproduce the problem. You can download it over at my AnswerHub post if anyone wants to try it out to see what results they get.

I noticed the same. Not for the AI movement replication itself, but when doing other things in parallel. When having 25 AI Actor moving around and starting some actions which relocated from server to client, they have some higher lag. I also have some minor meshes in the world with physics simulations on, when I hit around 20 AI characters moving, the physical simulation of the the actors (which are set to replicate movement also) begins to get really, really laggy and rubber-banding.
Welcome for any advises.

I also need help with this. Does anyone know of a guide on how to reduce rubberbanding on AI movement with blueprints? I find it annoying that my players’ movements are fine while AI rubberbands. I think this is the last challenge I will be facing for my project.

Do I have to pay someone to teach me? Where do I find a ue4 teacher?

I haven’t tried it yet, but there is a new tool for analyzing the network performance.…hts/index.html