multiplayer

[thin stratus]

And I cut away that function for my own

But that's not required

[grizzled stirrup]

I've recreated AGamemode and AGameState in the last few days

Just to learn how they work

Was very beneficial

It's doing way more useful stuff than I ever knew

[thin stratus]

Yeah for me it's enough to read through them

[grizzled stirrup]

I was repeating so much work

I find I have to actually go line by line to fully get it

But I'm not very experienced in code

[thin stratus]

If you need more info, just check UT source code

A lot of what I'm sharing here is basically from there

[grizzled stirrup]

When you say "I cut away that function for my own"

Do you mean you don't use OnMatchStateSet() and use something custom?

[thin stratus]

Yeah, but can't recall why we do this

It's basically the same

[grizzled stirrup]

Cool yeah I made some minor changes when recreating, just slight different names

Like one big gotcha

They use an FName property MatchState but also name the namespace MatchState

Which means that if you define a new FName MatchState in a derived class, it will be confused and think you are talking about the FName and not the namespace when you type it out

Someone in cpp suggested to change MatchState to MatchStates and it's way clearer now

So MatchState will always refer to the FName and MatchStates will always refer to the namespace

[glass plaza]

In the case of bandwith, is FTransform optimized enough to use it instead of a FVector and an FRotator if I don't intend to use the Scale?

(I only need Location/Rotation)

[thin stratus]

Don't think so

Epic packs Rotation quite heavily when sending it in the CMC

[brittle karma]

any idea how to fix Advanced Vehicle's laggy Movement for client? its very laggy by default

[thin stratus]

@grizzled stirrup To get back to the RapidFireWeapons, you would use pooling for that and most likely use LineTraces + fake projectiles locally.

That's at least what we did in the end.

Only the actually big projectiles are visible

[grizzled stirrup]

I use hitscan only

I just mean for each impact

Needs an RPC

Usually at least one RPC per shot

Unless doing the started firing RPC and then stopped firing RPC

But I'm not for a few reasons (many semi auto weapons mainly)

The point was that there's usually a lot of general traffic going on (server verifying hits / movement being evaluated etc, so an int could probably sneak on one of those outgoing packets without too much disruption once a second)

Though I know this is avoiding the problem rather than fixing it as you are

But for the sake of simplicity, at least initially I might try it

[thin stratus]

We replicate a BurstInterger

[grizzled stirrup]

Can always upgrade to a more elegant and bandwidth effective method later if needed

[thin stratus]

That increments each shot

And resets to 0 when stopping

Local Client fires the weapon anyway

[grizzled stirrup]

The server has to replicate the impact to everyone though right?

[thin stratus]

And the rest simulates with an Onrep of that integer

No, everyone fires the weapon

Only the Server deals damage

[grizzled stirrup]

Oh right yeah sorry

So one RPC per shot

Updates the burst int

OnRep to everyone

[thin stratus]

It's a RepNotify variable

[grizzled stirrup]

Yeah I think I have it set up similarly

ShooterGame was the main ref on the setup

[thin stratus]

And yes, Client fires, Client tells Server to Fire. Server Fires and increments Int. Int replicates and the Simulated Clients fire.

And the random seed for spread gets reset every time the weapon stops firing

[grizzled stirrup]

I'm curious, how are you dealing with lag compensation?

Or are you allowing the clients view to count?

Or doing something like ShooterGame (checking a broad area around the shot)

[thin stratus]

No, we aren't doing any of that yet

[grizzled stirrup]

That's where it gets tricky and why I'm never making a competitive shooter 😄

[thin stratus]

Yeah but our shooter is pretty fast to begin with

[chrome bay]

lag comp isn't too hard tbh

[grizzled stirrup]

Luckily with Co-op you can trust the client a lot more

Because who cares if he cheats

[chrome bay]

You just need to store a small buffer of transform history server-side, interpolate between it and check location roughly matches. So long as you know roughly when the client fired relative to the server time (which you can determine from ping) - you can verify that the clients target was roughly where they thought it was when they hit it

[grizzled stirrup]

It's the caching of the hitboxes that always truips me up

Going back and firing at timestamps isn't so bad

But caching, I always mess it up

[chrome bay]

If the hits never change size you don't really need to.

[grizzled stirrup]

I think the key that I should have thought of is what you said "roughly"

I should allow the shot if it's around where the player was

Instead of trying to be exact

[chrome bay]

Yeah, it has to be roughly. There's no other way to verify it otherwise - animations could be in wildly different states etc.

[grizzled stirrup]

But then I had problems like should I allow the client to say it was a headshot and the server just checks if it was roughly a headshot?

Even if the client might have hit the shoulder legit but told the server it was a headshot

And yeah anim states

That was the main thing to trip me up

[thin stratus]

What i never understood is, even if I have a timestamp, how do I role the server back?

[grizzled stirrup]

Not only hitboxes but anim position

I believe you literally set the transforms of the hitboxes within a function on the server, do the trace and move them back

[chrome bay]

It gets infinitely harder when your bullets are hit-scan

[grizzled stirrup]

All in the same frame

So nothing really moves

[chrome bay]

Then it's a royal nightmare

[grizzled stirrup]

Yeah all mine are

[thin stratus]

Yop

[chrome bay]

are NOT hitscan i mean.. oops

[thin stratus]

Ah

We only have explosions and slow moving stuff that are actually projectiles

So they can miss

fuck that

[grizzled stirrup]

Slow projectiles are great because the server handles them nicely

UT / SG style

[chrome bay]

If you have bullets which travel, you (might) need to roll the projectile back in time too... then it becomes pretty much impossible

[thin stratus]

So you'd keep list of recent timestamps + location

[grizzled stirrup]

Fast projectiles... ugh

[thin stratus]

But damn, that sounds like it should be part of UE4 already

[grizzled stirrup]

They have a generic lag compensation component planned

Really hope it gets added soon

I gave up because it was just too many headaches adding on top of one another

[thin stratus]

Do you move the actual actor back to where it was? Doesn't that replicate, how the f do you roll back the server by not actively rolling it back

[grizzled stirrup]

Tha anim states being the icing on teh cake

Because it's being moved back in the same function

So it never moves

[chrome bay]

Epic are doing a generic prediction system I think, but not lag comp

[grizzled stirrup]

Move -> test -> move back

[chrome bay]

But for hit-scan, lag comp is super easy

[thin stratus]

Well if it's so easy, then let me know how that works on the serverside?
I can send the timestamp to the server when I fire, what does the Server do then?

What is given by epic and what do I have to setup.

[grizzled stirrup]

There's a good implementation in UT code

[chrome bay]

For hitscan I don't send any timestamps

Basically, I have this:

[grizzled stirrup]

Basically constantly cache player positions and then roll back and iterp to the exact position at the time of the shot, then recreate the trace, then move everything back to the current time

[chrome bay]

IST_NetworkRewindInterface::SaveRewindSample(const bool bTeleported = false) = 0;```

[grizzled stirrup]

I gave up when I watched how COD does it- every bit of state is exactly the same, animation being so important since you could be prone, rolling / in widely different positions to default

[chrome bay]

The server is calling SaveRewindSample() after physics runs, and that just gets dumped into a circular buffer and saves WorldTimeSeconds along with it

There's a function for interpolating between samples back in time (and it stops at the last sample if there was a teleport)

[thin stratus]

WorldTimeSeconds is a TimeStamp though, so how do you know to what to rewind to?

[chrome bay]

Ping

As soon as you get the RPC, the time the client fired is approx CurrTimeSeconds - PingSeconds

So that gives you the world time they fired

[thin stratus]

And Ping is already avaiable from the CMC/Character shizzle i guess

[chrome bay]

Yeah and PlayerState (where I get it from)

[thin stratus]

Is PlayerState ping back and forth or only one direction?

[chrome bay]

I think ping is RTT

so.. take with a pinch of salt

but it's usually close enough

[thin stratus]

Right, still not 100% sure how you actually do the Trace test then on teh Server side, cause you can't actively move the whole collision back in time or?

[grizzled stirrup]

    for (int32 i = SavedHitboxPositions.Num() - 1; i >= 0; i--)
        {

            TargetLocation = SavedHitboxPositions[i].Position;
            if (SavedHitboxPositions[i].Time < TargetTime)
            {
                if (i < SavedHitboxPositions.Num() - 1) // ??
                {
                    PrePosition = SavedHitboxPositions[i].Position;
                    PostPosition = SavedHitboxPositions[i + 1].Position;
                    if (SavedHitboxPositions[i + 1].Time == SavedHitboxPositions[i].Time)
                    {
                        Percent = 1.0f;
                        TargetLocation = SavedHitboxPositions[i + 1].Position;
                    }
                    else
                    {
                        Percent = (TargetTime - SavedHitboxPositions[i].Time) / (SavedHitboxPositions[i + 1].Time - SavedHitboxPositions[i].Time);
                        TargetLocation = SavedHitboxPositions[i].Position + Percent * (SavedHitboxPositions[i + 1].Position - SavedHitboxPositions[i].Position);
                    }
                }
                break;
            }
        }

[chrome bay]

So when you get the RPC from the client it usually has "ShotOrigin and "ShotDirection" - so you just redo the shot

[grizzled stirrup]

I remember I took most of this from UT which is how they rewind

[thin stratus]

Yeah I just send "Fire" and the Server takes the current Origin and Direction by tiself

[grizzled stirrup]

But remember even if you rewind perfectly, the anim state is stale which means if the player was prone or in some other position it still wouldn't be accurate

[thin stratus]

But that can be changed of course

[chrome bay]

Ah yeah in that case a bit harder, but yeah that's the idea anyway

[thin stratus]

We have no animations in that regard

So I don't have to care about that

Our drones have the same shap at all times

[grizzled stirrup]

That's very lucky

That's the hardest part I feel

Even with perfect rewinds

[chrome bay]

I honestly don't think it's worth doing individual hitboxes, I just trust them within a small tolerance

[thin stratus]

so you just redo the shot
Well yeah, but it won't hit ,cause the Server is a few ms furtehr now.

[grizzled stirrup]

I believe a solution there is actually store the state of every hitbox

But yeah it's a waste

And still hard to do

[chrome bay]

The main thing you're trying to prevent is the client blatantly cheating

[grizzled stirrup]

Honestly the ShooterGame approach almost does that well enough- almost

[chrome bay]

And you want to clamp the maximum time it rewinds too so that players with 500ms ping don't get some huge advantage

[grizzled stirrup]

It's such a big leap in terms of bandwidth and complexity otherwise

[thin stratus]

Do you check by hand if the shot hit? :P I really don't get how the Server LineTrace with the old location can hit something.

[grizzled stirrup]

You move the player and hit enemy back to where they were at the time of the shot (on the server)

Trace

See if it hit

Should line up roughly to what the client saw

[thin stratus]

I can't just move stuff back, that will replicated to clients(?)

[grizzled stirrup]

It won't because you move them back in the same function

Nothing has a chance to replicate

[thin stratus]

So you really just teleport the freaking actor back to where it was, perform the shot and teleport it to the actual location?

Mother of god

[grizzled stirrup]

Haha yep, it's a mindbending nightmare

[chrome bay]

Hell I don't even do that

[grizzled stirrup]

Check out the UT implementation I believe it does it

[chrome bay]

primitive components have a function where you can perform a line trace against them in any arbitrary location/rotation

So I just trace the root component at the rewound transform

[thin stratus]

THAT'S what I meant with "UE4 probably has something"

That function is bascially the missing thing I needed to understand how you rewind

[chrome bay]

yeah that's what I'm doing anyway

You could move the actor forward and backward I guess but meh.. fuq dat

[thin stratus]

Saving locations and stuff is easy enough, but actually testing against a location that no longer exists is what confused me

[grizzled stirrup]

I might be very wrong, it's been a while since I was doing it

Checking the UT code now

[chrome bay]

But yeah.. once travel time is introduced everything goes to shit since if the projectile is moving slowly enough there could have been loads of world-state changes since then

[grizzled stirrup]

https://blog.bluecurse.com/2017/09/18/lag_compensation_part_1/

Very useful guide though I think it's unfinished

Covers the per hitbox approach

[chrome bay]

See the massive problem with that is what happens when the animations don't match (which they never will)

You have to allow for some tolerance anyway then, at which point you may as well just trace the capsule anyway

We don't even play animations for characters on the server in HLL

too expensive to eval 100+ anim graphs

[grizzled stirrup]

Yeah honestly I gave up after a while and am now just doing simple client side approximations haha (as I can do it for a co-op game)

It's so much more complicated when you have to rewind for every shot and cache so much

[chrome bay]

This series is no longer being worked on for the foreseeable future Maybe they realised 😄

[grizzled stirrup]

😄

Props to anyone building a properly lag compensated MP game in UE4

[thin stratus]

Tbh, the big studios cheat more than their gamers

In terms of allowing client hits etc.

[thick creek]

If a USTRUCT has a custom NetSerialize function, are variables of the struct not used in the NetSerialize function still replicated or does defining a custom NetSerialize mean that only variables added to the FArchive are replicated instead?

[grizzled stirrup]

Yeah so many games allow SO much from clients

Very few seem to have full rewind implemented

[chrome bay]

@thick creek Only the data in the FArchive is serialized and sent

[thick creek]

@chrome bay Cool that's what I thought. Thanks 😃

[grizzled stirrup]

I doubt any BRs do due to the already huge bandwidth strain

[chrome bay]

@thick creek Bear in mind btw that the whole archive will be sent each update too, they don't support replicating individual properties within structs then (so when the struct changes, the whole struct replicates)

It's a bit of a balancing act

[thin stratus]

I do think a lot of those things come from Devs being pushed by Publishers

They just don't have the time to add it

[grizzled stirrup]

And simply put, the more clientside you are the better it feels (as the shooting player) unless the lag comp is implemented extremely well it can feel like you missed shots you should have hit

Or even worse, fully serverside

Which I don't think any game does

[thick creek]

@chrome bay So if a struct doesn't have a custom NetSerialize, then it would only replicate the individual properties that change?

[chrome bay]

Yeah that's right

[thick creek]

Neat, thanks for the information 😃

[brittle karma]

any idea how can i fix Advanced vehicle's Client Movement issue? its so laggy by default

[chrome bay]

@brittle karma use client-auth and hope for the best

[brittle karma]

what?

[chrome bay]

It's laggy because there's no prediction or smoothing for it - you have to either implement that (nigh on impossible) - or use client-authoritive physics

For a quick out-of-the-box solution anyway

[brittle karma]

so wheeled vehicle's Movement Component is sucky we assume

[grizzled stirrup]

If you were writing a RespawnAll() function which would ensure everyone gets freshly respawned even if they are currently possessing a pawn, is it acceptable to do something like this before respawning?:

        APawn* OwnedPawn = ControllerToRespawn->GetPawn();
        if (OwnedPawn)
        {
            ControllerToRespawn->UnPossess();  // Or maybe PawnPendingDestroy(); ?
            OwnedPawn->Destroy();
        }

[chrome bay]

Physics and Networking is sucky in general

It's a minefield of hurt

[brittle karma]

@chrome bay What exactly do u mean by client-authoritive , cuz all in all server should tell everyone the client has moved or things like this

[chrome bay]

It just means that the controlling client tells the server where it is, and the server replicates that to other players

[thin stratus]

Yeah it should, but only the Simulated peeps

[chrome bay]

There's a checkbox in the Vehicle Skeletal Mesh

Replicate Physics To Autonomous Proxy or something - uncheck that

In 4.21 and above

[thin stratus]

Does the Vehicle do any Prediction?

[chrome bay]

negative 😦

[thin stratus]

I mean otherwise it's kinda laggy when you just send the Server where you are

[chrome bay]

All it really does is just ignores replication from the server when the pawn is an auto-proxy

So you can at least move instantly without being snapped around all the time

[brittle karma]

@chrome bay ok let me uncheck that that and ill tell u the result

@thin stratus well i just used the default advanced vehicle and i didnt change anything, they implemented it this way

@chrome bay thanks, now its so smooth, it made me crazy i was searching for hours

[worthy wasp]

Question - COND_OwnerOnly conditions - I imagine that an RPC sends data to server - and the server back to the player in replication ... I was looking to use this condition as a means of Cheatproofing on a Dedicated server - is this a viable option?

client would RPC(Server) and the server sets the variable

[thin stratus]

OwnerOnly means that it only replicates down to the Owner

So simulated won't get the update

[worthy wasp]

i undesrtand that

"I was looking to use this condition as a means of Cheatproofing on a Dedicated server"

and wondering if this would suffice that ?

or if theres a better (authoritative) way to do this?

the variable does not need to replicate to others - but it does need to be authoritative

[chrome bay]

That's the way to do it yeah

If only the owner of the actors needs to get that var, using that flag will make that happen

[worthy wasp]

thanks

[plain lagoon]

is it possible to have multiple "server levels" on a dedicated server? I currently have a level that acts as the login which connects to the server, when logged in it will send you to the "lobby level" with an openLevel node, but when I send two or more clients there it looks like they are both in their own level. does anyone know why this happens? (I'm fairly new to unreal multiplayer, so it might be something really dumb)

[winged badger]

@thick creek if you're diving into custom serialization, i warmly recommend reading bool FHitResult::NetSerialize(FArchive& Ar, class UPackageMap* Map, bool& bOutSuccess)

its an excellent example

@plain lagoon use seamless travel

[thin stratus]

@plain lagoon

1. Moving between Levels on a Server has to be done via "ServerTravel" and has to be issued by the Server.
2. All Clients will move at once with the Server.
3. You can't have more than one Level on a DedicatedServer (not counting Streaming Levels).

@winged badger That would still not give the person the ability to have one player in Lobby and one in Gameplay Level on the same Server, or?

[winged badger]

nope

[plain lagoon]

hmm, so I would need to have my login system in the same level as the level i let players play in. that's a weird one

[winged badger]

dedi can run multiple instances of the game

[plain lagoon]

you'd expect unreal to have a better system for that

[thin stratus]

So you need a Server for the Lobby and one for Gameplay. It could be in the same level if your lobby is just UI

Well, that's the same reason you always travel together in Borderlands

One Server, one Map

[winged badger]

you can however gimmick a lobby not using unreal's own networking

if thats easier for you

using steam lobbies for example

[plain lagoon]

how do all those mmorpg's made by unreal have so many different area's though, can't all be one huge level, right?

[winged badger]

could chat, and exchange some data, but not much else

[plain lagoon]

or do they use an external system/a bunch of separate dedicated servers

[thin stratus]

Either they don't use Dedicated Servers

Or they use a smart backend that manages them

[winged badger]

with Unreal, the way for those is middleware like SpatialOS

[thin stratus]

But in general, DedicatedServers by UE4 are more matchbased, than MMO

So 16-32 Players UT

Or by now 100 player BattleRoyal

So MMOs rather use what Zlo linked

[winged badger]

SpatialOS allows you to distribute the load between multiple dedicated servers

[plain lagoon]

ohhh that's really cool

[winged badger]

while still using unreal networking

[thin stratus]

Remember that most third party solutions cost money

So if you don't want to spend a lot, this isn't the right thing for you

SpatialOS is not for free, neither is hosting a large amoutn of Servers

Bigger Team and Funding are more or less needed for stuff like this

[winged badger]

and, since its no way mentioned enough in this channel: best not to try a MMORPG for your first game

[thin stratus]

Or just a bigger bank account :P

[plain lagoon]

nah im not gonna try an mmorpg

no worries

i just wanna try some prototyping for a small game similar to the fable legends 4 players vs 1 villain concept

• i wanted to practice unreal multiplayer stuff

[winged badger]

you are using c++?

[plain lagoon]

yah

[winged badger]

good

[meager spade]

the clients need to travel

oops delayed

[winged badger]

GameMode will fight you tooth and nail if you want asynchronous gameplay

[thin stratus]

If it's just for practicing, stick with ListenServers

[plain lagoon]

blueprints for the simple prototyping tho

[winged badger]

you'll pretty much have to override the entire thing without calling Super 😄

[plain lagoon]

oh no

notlikethis

[winged badger]

for starters, it insists, by default, that all PCs are of the same class

[plain lagoon]

aight time to switch to unity

[winged badger]

while it can be persuaded to change its mind, it usually requires rewriting the whole thing

good news is that most of what you need is in the GameMode already, in one form or another, like swapping PCs in HandleSeamlessTravelPlayer

[thick creek]

@winged badger Thanks, I was extending a struct that used NetSerialize. I think I figured it out 😃

[plain lagoon]

in my head the game should be super easy

its just the network part i have to figure out

[thin stratus]

Start by reading my compendium

that's what it's for after all ¯_(ツ)_/¯

[plain lagoon]

yeah i did that

but after that i was like

ok, now how do i start

[thin stratus]

I have a simple issue that requires you to understand the networking stuff

Place a Door into the Scene

And make it so the client can open it for everyone visible

And at best, set the RelevancyDistance of that door low, and make sure players who come in from afar also see it being open

Cause this simple "Door" problem, requires you to use RPCs, understand Ownership, utilize RepNotify etc.

Once you have that working, it'll be easier

[plain lagoon]

ima try that after i manage to get 2 players in the same level

cause i couldnt even manage to do that

[winged badger]

btw

do not do exi's door excercise by making them open on overlap

because that would beat the purpose of it

[thin stratus]

OH yeah sorry, they need to open them by pressing E

Or whatever key you want

[plain lagoon]

wouldnt matter tho, right?

as long as all other players can see it

[winged badger]

overlaps run on server and client

[plain lagoon]

ah

[winged badger]

so as long as the door is set to open on overlap

[plain lagoon]

yeah then it matters

[winged badger]

there is no networking required

it just... works

so not really a great excercise

[thin stratus]

Yop, and it's really tricky to get the E press to open the Door if you didn'T understand the Ownership RPC stuff

Note: I ran into that problem as a beginner and that's why I like it :D

[plain lagoon]

i'll try it after getting both players in the same level

and hope i dont fuck up

i understood the document pretty well

i think

[thin stratus]

Gnah, just had a bug where I used a function to pass "int32, bool, bool" and one call use "true, true" while another use "30, true, true"
And i was like "WHY IS THE INTEGER 1!?!?!"

(solution: You should not pass true for integer if you don't want it to be 1, but rather "0, true, true")

[high current]

You guys had doors to RPC in the beginning

I had to replicate physics the first time I did MP...

[plain lagoon]

that's why im practicing rn

so that i wont suddenly have to do something like that without knowing anything

[high current]

Yeah, thats best

[winged badger]

My start was networking a non-networked game... ugh

[grizzled stirrup]

Aka rewriting it 😄

[timid moss]

does ejecting while playing on a client keep you on the client? or does it put you on the server when you hit the eject button?

[high current]

What eject button

[soft relic]

How could I set a dedicated servers name and max players so it would show up in my servers list as the player's sessions do?

[high current]

@fluid flower most recently fiddled with that. IIRC it had something to do with ?maxplayers= in the ini and some things in AGameSession

[soft relic]

Okay!

Are dedicated servers something that is differently setup for each game? I mean, could it be setup in a marketplace product or it would be useless and would have to be redone?

[high current]

dedi servers are compiled from source for each project

what do you mean by setup exactly, the setup to build a dedi server for your game, or some gameplay logic setup?

[fluid flower]

yeah for me the command line way did not work consistently, but putting maxplayers in the ini file did work fine

[brittle karma]

is there any problem with calling timer like this in an RPC?

void AMyPawn::Respawn(SpawnTransform)
{
    if(Role < ROLE_AUTHORITY){
        Server_Respawn(SpawnTransform);
    }
    else{
        //codes for calling other classes for doing the job
        //...
        //code for calling this function after some seconds
                        FTimerDelegate TDelegate;
                        TDelegate.BindUFunction(this, FName("Respawn"), SpawmTransform);
                        GetWorldTimerManager().SetTimer(DieTimer, TDelegate, 1, false);
    }
}

it cuzes editor crash

well instead of FName("Respawn") i used FName("Server_Respawn") and it works fine now. [SOLVED]

but why is that? if i call Respawn itself it should work i guess🤔 cuz that code is already is called by Server_Respawn.

[high current]

pardon my complete innability to read C++ (yet), but isnt it running into stack overflow if you do FName("Respawn")

[brittle karma]

i dont think so, why?

basically its some sort of recursion

@high current as i mentioned in the code i didnt send the whole code. it definitely has a condition for itself ((:

[unborn spindle]

I feel absolutely stupid right now. I am running this to spawn an actor, it runs on the server, everything in the actor, its parent, every component is set to replicate. But its only appearing on the client who I call the spawn from. However the torch still has collision with the client that cant see it. I thought this was straight forward, run on server and replicate it. The hell.

And it works now. I guess I had auto-active ticked. Dont know what that would effect.

No it was actually my cull distance. Okay. Werid

[timid moss]

hi. Right now i have if(Inventory.IsValidIndex(0)) { //Do stuff }is it necessary to instead doif (Inventory.IsValidIndex(0) && Inventory[0]) { //Do stuff }

[royal isle]

@timid moss If your array is an array of pointers then yes. IsValidIndex() will check whether the number is a valid array index but that index could very well store a nullptr value so you need to check for that too.

[fluid prawn]

Does anyone by any chance know what function call or CVar is used to display debug information about acceleration and velocity for the CMC? I've seen in game displayed over a 2D graphs but not sure how they are getting it.

[high current]

New cod game switches between hitscan and projectiles for their weapons

'if it were to reach a target within a frame [one 60th of a second], it would be hit-scanned, so up to a range that we feel is healthy [and accurate], you still retain that ‘my icon sights are on the guy, and that will hit him, and I’ll get the hit marker and everything’.” Or to put it another way, at close and mid-range, and depending on the weapon you’re firing, expect an instantaneous hit from your weapon’s ordnance.'

I wonder if it is 0.16 capped or if it will actually be delta time

Would be funny if it is delta time

If you play the game at 24 fps, you will be hitscanning everyone... :d

[worthy perch]

When traveling from map to map (seamless, if that matters), I sometimes get this or a variation on this:

LogNet: Warning: UActorChannel::ProcessBunch: SerializeNewActor failed to find/spawn actor. Actor: None, Channel: 9
LogNet: Warning: UActorChannel::ProcessBunch: SerializeNewActor failed to find/spawn actor. Actor: None, Channel: 12

I don't think this results in any actual problems.
I'm not really sure how I should resolve this issue. If Actor: None, is the map dirty or something else?

[winged badger]

tried finding the line that prints the warning, putting a breakpoint

and seeing which Actor its trying to serialize?

[plush mist]

Hi! Does anyone work with Crowd manager ? Its setup properly for avoiding each other and I'd like it. But some times AI has some jittering when avoid each other or waiting to some space will be free for further movement. Is it possible to tweak crowd manager to stop jittering ?

[worthy perch]

Alright, just wanted to check if this warning was common and ignorable.

[plush mist]

I have client side physics based movement for my drone(Derived from Pawn). How can I easy replicate this movement to server ? in my case I don't need to replicate drone movement to other clients, just for server only.

[winged badger]

@worthy perch i have never seen it before

[grizzled stirrup]

Would there be any reason that BeginPlay on a freshly spawned AActor only runs on the client and not the server?

[bitter oriole]

Maybe you spawned it on the client

[grizzled stirrup]

It's spawned from the GameMode

Really odd since it's a bread and butter spawn, nothing different going on at all

If I make a function InitActor and directly call it after spawning, it runs fine on the server

But of course not the client then

BeginPlay should work just fine as it did in earlier tests with similar actors I did

[winged badger]

deferred spawn?

[grizzled stirrup]

Nope it's as simple as this: SpawnedActor = GetWorld()->SpawnActor<AActor>(ClassToSpawn, SpawnLoc, SpawnRot, SpawnParams);

It does spawn on both client and server it seems

But doesn't run BeginPlay() at all on the server

I have a log printing if it does

If I drag an instance of the class I'm trying to spawn into the world and press play- no begin play, if I hit simulate, it runs beginplay

[winged badger]

did any AActor function overrides on it?

[grizzled stirrup]

Just overriding BeginPlay()

And calling Super

[chrome bay]

BeginPlay is wierd online

Server calls it once the gamemode calls "Start Play"

[grizzled stirrup]

Ughhh

[chrome bay]

Clients call it on receiving the actor IIRC

[grizzled stirrup]

I'm calling the spawn after Start Play

Thank you so much

That makes sense now

[chrome bay]

Oh you should be fine then

Hmm

[grizzled stirrup]

Wait might be calling it right before start play super

[winged badger]

not if the world didn't start play

[grizzled stirrup]

It's in start play

Either way will try moving the spawn and see

[winged badger]

which goes via replicated variable in GS

[grizzled stirrup]

Hmm actually I'm calling it WELL after start play

Like 5 seconds after

[winged badger]

it is routed differently, on Server its called from PostSpawnInitialize

on client from PostNetInit

[chrome bay]

void AWorldSettings::NotifyBeginPlay() is what ultimately calls BeginPlay

[winged badger]

yeah

[grizzled stirrup]

And newly spawned actors don't run begin play after that?

[winged badger]

but they both use DispatchBeginPlay, which checks if the world did BeginPlay

[grizzled stirrup]

Actors spawned AfterNotifyBeginPlay is run?

Hmm

[chrome bay]

Man.. I can't remember now

[winged badger]

and client can't have the world BeginPlay unless server's did too

if GM didn't call DispatchBeginPlay

any spawned or loaded Actors won't BeginPlay until it does

when it does, all of them call BeginPlay

and any Actors spawned after call BeginPlay as last step in their construction

[grizzled stirrup]

Ok thank you so much

I'll make sure the GM calls DispatchBeginPlay (I remade AGameMode and they have moved the calls around a bit)

[winged badger]

but

that is not your problem

because when it calls it

it also sets tells the GS that its time

then it replicates a variable

and OnRep starts BeginPlay on client worlds

so only way you could achieve that is by making an error overriding StartMatch() i think

and it would affect all Actors, not just those of one class

[grizzled stirrup]

Yes you are right I just noticed that other actors aren't calling BeginPlay() only on the server

Will look into the StartMatch() implementation

thank you very much!

[winged badger]

might not be the right function, but its in GM

[grizzled stirrup]

Yep I have the general flow of events quite fresh since recreating

[winged badger]

and it has to do with match start

[grizzled stirrup]

But I bet I didn't make a call somewhere

Thanks

[winged badger]

(it would have to tell GS to start match, but not call DispatchBeginPlay on world)

[grizzled stirrup]

That was it, thanks a lot Zlo!

``
// Calls begin play on actors, unless we're about to transition to match start

if (!ReadyToStartMatch())
{
    GetWorldSettings()->NotifyBeginPlay();
}

``

My implementation of ReadyToStartMatch() differed, so in my case, I WAS ready to start the match, so it didn't call NotifyBeginPlay on the server

I'm not entirely sure of the logic here as surely you'd always want NotifyBeginPlay to go out, especially if you are ready to start?

It works fine again for me if disable that if check and just call NotifyBeginPlay when HandleMatchIsWaitingToStart is called

[thin stratus]

@grizzled stirrup

    // In case we went into this so fast that the world isn't playing yet, notify it!
    if (!GetWorld()->bBegunPlay)
    {
        GetWorldSettings()->NotifyBeginPlay();
    }

We do this too, not sure what the topic is

:D

[grizzled stirrup]

Great bool check example thanks a lot

Yeah it seems like a bit of a weird check in AGameMode

[thin stratus]

I think we only did this when we instantly jumped into a matchstate that required this to be true

Which only happened in PIE

So I doubt we actively use that

[grizzled stirrup]

Yeah I think it's happening because of the check that sees if you can play at the instant PIE starts

In StartPlay

``
// Check to see if we should immediately transfer to match start
if (MatchState == MatchState::WaitingToStart && ReadyToStartMatch())
{
StartMatch();
}

``

I'll probably even disable this logic and always have a delayed start

Thanks for the solution though and glad I'm not the only one to have ran into it, was very confusing!

[thin stratus]

Right, what you can do is: delay it by one frame

iirc UT does that

[grizzled stirrup]

You can do that with a timer that has a delay of 0.0f right?

[thin stratus]

well actually

bool AHLGameMode::ReadyToStartMatch_Implementation()
{
    checkf(HLGameState, TEXT("[%s] No valid GameState."), *GetName());

    if (!bDelayedStart)
    {
        // starting on first frame has side effects in PIE because of differences in ordering; components haven't been initialized/registered yet...
        if (GetWorld()->TimeSeconds == 0.0f)
        {
            GetWorldTimerManager().SetTimerForNextTick(this, &AHLGameMode::StartMatch);
            return false;
        }
        else
        {
            return true;
        }
    }
[...]
}

We do this too xD

[grizzled stirrup]

Oh I did not know about the SetTimerForNextTick() function

Really useful thank you

[thin stratus]

Yeah it's the Delay with time 0 :D

[grizzled stirrup]

One other timer related thing: in AGameState and also around the ShooterGame GM, they call a timer like this in PostInitComponents() GetWorldTimerManager().SetTimer(TimerHandle_DefaultTimer, this, &AGameState::DefaultTimer, GetWorldSettings()->GetEffectiveTimeDilation() / GetWorldSettings()->DemoPlayTimeDilation, true);

However they ALSO call that line within the DefaultTimer function itself

Since they are both set to loop, does this mean that when the second looping .SetTimer() call is made, it cancels the first?

I am simply not calling it a second time within the DefaultTimer function and so far am not noticing any side effects ,but maybe they are doing it for a reason

[thin stratus]

Calling the same timer with the same timerhandle again will reset the first one

[grizzled stirrup]

Ok cool thanks for the help!

[grizzled stirrup]

Is there any way to easily see more details for crashes on builds when testing with Steam? Getting a hard crash only when there are two Steam players in a game after seamless travel

[2019.08.14-16.13.10:015][379]LogWindows: Warning: CreateProc failed: The system cannot find the file specified. (0x00000002)
....

[2019.08.14-16.13.10:015][379]LogWindows: Error: === Critical error: ===
[2019.08.14-16.13.10:015][379]LogWindows: Error: 
[2019.08.14-16.13.10:015][379]LogWindows: Error: Fatal error!
[2019.08.14-16.13.10:015][379]LogWindows: Error: 
[2019.08.14-16.13.10:016][379]LogWindows: Error: Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x00000380

[2019.08.14-16.13.10:016][379]LogWindows: Error: [Callstack] 0x00007ff767717b9b MyGame.exe!UnknownFunction []
[2019.08.14-16.13.10:016][379]LogWindows: Error: [Callstack] 0x00007ff767bef3d9 MyGame.exe!UnknownFunction []
// A long list of UnknownFunction calls finally followed by 
[2019.08.14-16.13.10:016][379]LogWindows: Error: [Callstack] 0x00007ffc75f17bd4 KERNEL32.DLL!UnknownFunction []
[2019.08.14-16.13.10:016][379]LogWindows: Error: [Callstack] 0x00007ffc77c4ce71 ntdll.dll!UnknownFunction []

Looks like something is just null somewhere but there are many things that it could be and it works fine when testing solo

Is there a way to reveal the function names in the callstack or even better, the name of the property that was null?

Oh just found the "IncludeDebugFiles" checkbox in project settings, will try that now. If there are any other suggestions please let me know, thanks!

[bitter oriole]

You can use the generated minidump

Open it in VS, click debug, show where pdb file is, done

[grizzled stirrup]

Oh thank you!!

I've opened it in VS now and it shows the summary

Will try to debug now

What is the pdb file? As in the solution file?

[bitter oriole]

No, PDB file

[grizzled stirrup]

Ah found it in the build!

[bitter oriole]

It's generated alongside your executable

[grizzled stirrup]

Thanks

Wow it works great

MiniDump files finally make sense 😄

[unborn spindle]

Good morning. I am looking for advice regarding Net Cull Distance Squared and actor relevancy not working as expected. I am spawning a simple light emitter actor with a Run On Server event from the player character. I leave the owner pin empty. I have the Net Cull Distance Squared set rather low for testing to see the torches pop in and out.

Two peculiar things are happening. First only some of the spawned actors ever appear at all for other clients. Secondly the actors spawned from a specific client always show, always seem relevant. The checkbox for owner relevancy is unchecked and there is no owner assigned to the torch actors, as far as a print string debug showed.

[unborn spindle]

I have recorded a video showing the issues.

https://www.youtube.com/watch?v=WqlDSMZtdOY&feature=youtu.be

[unborn spindle]

Also want to add that I dont have any issues with the torch actor appearing when the Net Cull Distance Squared is set to the default values.

[brittle karma]

hey everyone. im having a weird issue here, i dont overlap an specific actor with the player, but it triggers the Overlapping Event and the OtherActor is the player which didnt overlap that object at all, client has this issue, server works fine

to be specific, that object which gets overlapped by the player, is Replicated actor, i checked if in the BP the Replicated check box is not set as it should, but its checked for replicated as well as cpp.

is it even possible? server player go the same path and its fine for him but client triggers the event

[winged badger]

option A - your client player left a primitive component where it should not be

option B - the other Actor participating in this is not on same location on server/client

[brittle karma]

actually it calls the Overlap Event in Specific location

rodes Z location is 0, and the OtherActor which is responsible to detect the Overlap's Z location is set to -1000

only client has this issue by the way

the whole road(which players are in) 's Z location is 0. so logically its not possible to Overlap the OtherActor, unless the player fall from the road(which i want to overlap the actor and it works fine )

[winged badger]

those screenshots don't look like client's world at runtime

[brittle karma]

no its only shows the the locations of road and the other actor

[winged badger]

and what you just said didn't eliminate either of the options

well, B is unlikely

[brittle karma]

i didnt get A can u explain it a little bit?

[winged badger]

say one of your scene components on the car is set to replicate

and you have some locally spawned meshes

and it decides to replicate its attachments

result is that any meshes attached to it, or its children that are not NetAddressable will just... fall off

and if any of your cars primitive components ends up down there, it will cause the overlap

doesn't need to be the whole car

[brittle karma]

aha got it let me check

its this,

Rep...to Autono...

well when i check this, client's movement starts to be 100 percent rubish

[winged badger]

you either added primitive components locally at runtime or didn't

you should know that

[high current]

question tho, why don't you count only server overlaps and ignore client ones

I mean, if you need the overlap for a cosmetic effect

sure

but if your overlap is gameplay dependent I would trust the server, not the client

[brittle karma]

@high current well the overlap is gameplay, and server do the job for client, its like this::
overlap happens ->
RPC fucntion is being called for the Pawn ->
in that RPC another function is being called in PC->
in the PC a function is being called in the GameMode'-> GameMode Restart the player`

so im sure server do the job cuz GM is only available on server.

@winged badger yeah i added a Scene Component to the car, and its Component Replication is unchecked

@winged badger any way to detect if the components are falling off from the mesh? i used cmd -> show collisoin to see if anything falls but it wasnt helpful

[high current]

you can put a break point on the problematic overlap and investigate yourself whay/why/how

[brittle karma]

im thinking of move the whole code into character class instead of wheeled vehicle. the movement component of wheeled vehicle is not good for multiplayer at all

[winged badger]

well, CMC won't do you any favors

[brittle karma]

@winged badger any idea to keep Mesh's Replicate Physics to Autonomous Proxy unchecked(cuz it make movement of client so ridiculous) and keep components in their possession and protect em from falling?

[worthy wasp]

maybe this is false positive reactions inside of PIE testing - but i just tried setting a REpNotify variable to COND_OWNERONLY - and the RepNotify function played to other virtual players (Again - PIE TESTING).

Should I expect to see this as its a default nature of RepNotify funcitonality? Or should the COND_OWNERONLY flag condition throttle this to only the owner?

#Confused

[winged badger]

it should replicate to owner only

due to nature of how BP RepNotify works, if others set that variable locally

the RepNotify will still fire

it just won't get updated from the server

[grizzled stirrup]

Does it matter if your OnRep function doesn't match the property name that triggers it?

Example:

    UPROPERTY(Transient, ReplicatedUsing = OnRep_IsPickupAvailable)
    ACharacter* PickedUpByCharacter;
    UFUNCTION()
    void OnRep_IsPickupAvailable();

[winged badger]

in c++ you basically bind the function by name with ReplicatedUsing specifier

so, no, it doesn't matter

or if it has OnRep

i have used same OnRep function for multiple related variables in the past

[grizzled stirrup]

Thanks! Not sure what you mean by the second last sentence

[winged badger]

it doesn't have to start with OnRep_

[grizzled stirrup]

Oh interesting I did not know you can have multiple variables trigger one OnRep

[winged badger]

its just a convention

[grizzled stirrup]

Ok cool so it can be completely unrelated like ReplicatedUsing = HelloUnrelated

[winged badger]

another thing you can do with c++ OnReps is

UFUNCTION() void OnRep_IsPickupAvailalable(ACharacter* OldCharacter);

[grizzled stirrup]

Yeah that's a super useful feature

Pass in the old value

I use it in a few places such as equipping weapons to have a reference to the old one

[winged badger]

DataChannel will use reflection to examine number of parameters in the OnRep

and call the appropriate overload

[grizzled stirrup]

Super clever stuff the engine does in that regard

[winged badger]

having to figure out the number of parameters and binding it by name in specifier

is why it has to be UFUNCTION

or UHT complains

[brittle karma]

@winged badger i did some tests, it seems child components are falling off cuz the overlapping event happens when i put hand break on in the sharp corners and turn. but the instigator of the event is still the Car itself as i printed it in Overlap event like
OtherActor->GetName()

[winged badger]

try printing the overlapped component instead

components falling off require a very specific setup

with an error in it

[high current]

Hmm, one more reason to switch to C++

BP gets mad as soon as you rename

had editor crashes cause of it

[grizzled stirrup]

I highly recommend using C++ for MP

[winged badger]

not being able to do anything with structs is the main reason to go c++

you can't use really useful things like FFastArraySerializer

you can't custom NetSerialize structs

you have to handle full UObject overhead if you want to call a function on the object

[brittle karma]

@high current well cpp is crazy in renaming, like 10 times more crazy than bp

[winged badger]

your OnReps in BP fire whenever variable is set, via replication or not

including on the machine that did the setting

which is just terrible

i also find the BP networked events really unreadable when you have 20 of them in the same class

[grizzled stirrup]

Not to mention you can't set COND_OwnerOnly or whatever for replicated properties in BP

Not sure if that's only for OnRep or not

But I believe it was a pretty big issue

[brittle karma]

@winged badger this is strange, i used OtherComp and it returned VehicleMesh

can we assume this as BUG?

[winged badger]

probably the bug you made

😄

[brittle karma]

but whenever i tick VehicleMesh's Replicate Physics Auto... it doesnt do strange behavior

well i dont want server side physics simulation

[brittle karma]

@high current do u know about component replication?

[high current]

whatcha need

[brittle karma]

i disabled server side physics simulation in the pawn

for the sake of making movement smoother

now it cuzes some weird behaviors,

Zlo said its about component replication but i couldnt understand much

now the root component 's replication situation is like this

and all child components of root component(which is vehicle mesh) are not replicated too

[royal isle]

The parent needs to replicate and then each component that you want to replicate needs to also be set to replicate

so tick ComponentReplicates

[brittle karma]

well i guess the problem im having is related to that Replicate Physics to autonomous

this is how it looks

[high current]

By default, the vehicle movement component does not have network prediticon

that is why disabling the rep phys to autonomous makes it smooth as you are kind of turning off replication and desyncing server/client

have you tried running server-auth physics actually

[brittle karma]

@high current server auth works fine but movement gets worse for client

[high current]

well so it doesnt work fine 😄

[brittle karma]

some sort of 😀

[high current]

Exi can tell you more about this, but to get stuff to work, you need some kind of prediction and correction from the server

I guess the other way is to go completely client-auth

and do overlaps on client and ignore the server completely

[brittle karma]

is there any links to read about it?

or at least what should i look for?

[high current]

https://www.youtube.com/watch?v=NMZVkevhytU

not really what I was looking for lol

Anyway, the best stuff I have seen/ read was where instead of setting location of the actor on the client when correcting

you are essentially constantly pushing phys forces tryin to match what the server is sending as the coorect position

so you are doing corrections by phys forces instead of set actor location

and it is still server auth

Peeps here will probably have a better solution tho. I guess it depends on how accurate you want your cars to behave

what exi did for HoverLoop, IIRC was a spring based system completely with just vector math and set actor locations ( no physics what so ever) and ofc the prediciton from the CMC

but if you are not using physics, your prediction is easy(relatively)

[brittle karma]

ok then, helpful info thanks

[high current]

https://www.youtube.com/watch?v=LG1CtlFRmpU

this is roughly what we use, but afaik exi replaced all physics with just vector math

Another thing which I am also curious is if the new net prediction plugin from Epic can work on the vehicle movement component easily. But TheJamsh is the person for that

I wish people from NewWorldInteractive kept an eye on this channel (and if they are, ty for the cool game 😉 )

I legit suspect the vehicles in Insurgency just have that Rep Phys to authonomous disabled and called it a day

But it was the same story with PUBG

[brittle karma]

😂

[high current]

when the vehicles first came out, they rubber banded like crazy

[brittle karma]

yeah right

[hollow bridge]

What is the best practice for a chest content replication? Obviously, I don't want the item list to replicate to all clients, since it's just relevant for the players that are currently interacting with

[high current]

Then assign proper ownership and replicate Owner_Only?

[hollow bridge]

And change the ownership whenever a player interacts with the chest?

[high current]

y

[winged badger]

alternative is having the chest spawn an ActorComponent on the player when its interacted with

that Component replicates the copy of the contents and also contains all required networking logic

either way you don't clutter the pawn

the Component approach is preferable if multiple players can interact with the item in question

at the same time

[vestal thistle]

Hello does anybody know a good way or the best way to create a dedicated server?

[vestal thistle]

or is there a website or resource that rents out dedicated servers for unreal?

[rich ridge]

@vestal thistle https://wiki.unrealengine.com/Dedicated_Server_Guide_(Windows_%26_Linux)

[vestal thistle]

Gotcha, the 4.18 is ok to work with 4.22?

Nvm seems all the same

[rich ridge]

Yes it works for 4.22, I myself followed this for 4.22

[mighty rover]

anybody ever get this error message running a dedicated server (v4.22.3)? Clearly you can see the files are there, and they are able to read them properly, it just won't load them. It's only happening on the physX dll's

[upper tendon]

Hey, whenever I try to join a multiplayer session, it gives me this error. anyone knows why? thanks

[high current]

probably because your player state is invalid

Does this happen the first time you try to join, or you get this error after a few times of trying

[upper tendon]

Every single time.

Can I fix it?

[high current]

I am assuming you are using BP

make sure you connect your player controller

to the join session node

[upper tendon]

I'll show you a screenshot

Pretty simple, nothing complicated

[high current]

and where do you run the Join Server node

[high current]

are you sure that the widget has it's proper ownership

widgets are local anyway, so you are allowed to just do player index 0

[upper tendon]

I'm pretty sure the ownership is proper

I'll try to un-link and and we'll see if its working

Okay, I think its working now, but just a quick question -
I didn't really set up the gamemode when a player join, doesn't it mean if the player joined, he can fly around, invisible? When the player join for me, he's invisible but can't move around.

[high current]

you need to have a playable default pawn and networked player starts

[upper tendon]

Alright, thank you!

[rose egret]

is it possible to replicate TSet or TMap

?

[winged badger]

its possible to make them replicate

but its not a very direct approach

[rose egret]

that kinda makes my code dirty 😦

[winged badger]

basically, flatten the TMap into 2 TArrays, put those inside a struct, replicate that, and re-assemble TMap OnRep

or, just make a struct to hold your data instead:

USTRUCT(BlueprintType)
struct FMyData
{
    GENERATED_BODY()

public:
    UPROPERTY(BlueprintReadOnly) TArray<Type1> Keys;
    UPROPERTY(BlueprintReadOnly) TArray<Type2> Values;
    TMap<Type1, Type2> Map;

    Type2 operator[] (Type1 Key) const
    {
        return Map[Key];
    }
    void Add(TPair<Type1, Type2> Element)
    {
        Keys.Add(Type1);
        Values.Add(Type2);
        Map.Add(Type1, Type2);
    }
};

something like that @rose egret

[high current]

is there a specific reason a TMap isn't replicatable, I have seen this pop up quite frequently and I am curious

[winged badger]

it still needs more work there, mostly to populate the Map client side, solved by

say FFastArraySerializer

[rose egret]

@winged badger 👍

[winged badger]

NetSerialization.h header has the docs for FFastArraySerializer

@high current i have no idea, you could replicate writing a somewhat inelegant custom NetSerialization function

as well

basically,

[high current]

yeah I couldnt think of a reason other than it might not support some key/value pairs, but then it should do others...

[golden aurora]

So... I have a dedicated server running Lobby Map but the session doesnt show up .. any ideia?

[winged badger]

what are you using for sessions?

[golden aurora]

The ideia was .. a player create a new map (session) to the others enjoy

but in here, this player is to be the dedicated server

[winged badger]

advanced sessions, uworks, manual implementation?

and player can't be the dedicated server

as there are no players on dedicated server

no LocalPlayer, no LocalPlayerController, no rendering...

[golden aurora]

I know

[upper tendon]

Turns out I forgot to set the Input Mode to Game Only haha

[high current]

oh yeah that is a common one

[grizzled stirrup]

For a simple co-op game with friends on Steam, are there any benefits to using Steam Beacons instead of a simple listen server host that creates a session and invites player directly to the menu map and then both seamless travel to whatever gamemode is chosen by the host?

From my limited understanding, it would seem that beacons allow you to join and communicate without actually creating a session or traveling

But I'm not sure if it's even worth setting it up if simple sessions can work similarly in my case

[winged badger]

you can also use steam lobby there

[thin stratus]

@grizzled stirrup Beacons are basically a connection without Level.
So you can do this in every level, and it's an extra layer of States (PlayerState/GameState).
It allows replication, but not sure to what degree.

They are mostly used for Partys, so if you invite someone you want to play with (friends), before actually searching for a server.
The Sessions are handled differently than Game sessions.
E.g. Party instead of Game (name). Steam doesn't allow more than one Session active at a time, so if you have a party, you'd need to tell everyone the gamesession to join to and then kill the party session before joining the actual agme.

You can later recreate the party if you save the Session info of the party

cause that's (with steam) a unique ID. So if the Host creates a Party again, they could rejoin based on the data.

For playing you always need the ListenServer GameSession

So beacons won't replace that

[strong sail]

Anyone know how too hide something on the clients side but show it on the server side

[thin stratus]

For all Clients or a specific one?

And who "owns" the object in question? @strong sail

[grizzled stirrup]

Thank you very much for the detailed explanation!

I guess beacons are very beneficial then in that case as you can easily back out of a game and retain your party info

And separating the party and actual game sessions like you said

[high current]

@strong sail disable visibility by default and enable it only on is server = true on begin play

or if the server is the owner, toggling only owner see

can do the trick

[grizzled stirrup]

@thin stratus Thinking on it a little bit more, if you never were going to be matchmaking with your party and only playing with 1-3 friends that join (the game wouldn't start until they have joined), would you say in that case it's easier for the host to just create a session in the main menu, have friends join and then seamless travel to the gameplay map instead of implementing a beacon party system?

[thin stratus]

I would not use beacons for that i guess

But i also wouldn't make them join in the mainmenu

Just make a new Lobby level

@grizzled stirrup

[grizzled stirrup]

Makes sense! If the host can still send invites from within that lobby level then it should work great

For example he invites friend 1 which opens the lobby map, sends the invite and creates the session

but then friend 2 gets online so they invite him while they are waiting in the lobby level

[unborn nimbus]

If you call a Server RPC from the server, does it skip the replication logic or is that overhead still there?

[grizzled stirrup]

AFAIK it's the same as calling a regular function, could be wrong though

[fleet raven]

it will be the same overhead as calling a normal local function through reflection

it will determine the call space to be local, skipping the replication and running it locally

[slender yarrow]

How do you handle important server variables that are floating around in UI's? I have a counter strike shop type UI that you buy kill streaks from. How would I safely alter variables that only the server should be handling? I feel like with my current setup the start of all these actions are in the UI and would be easily hackable.

I dont know how to word this 😕

[high current]

I do such things in the game state, (ofc with replicated vars)

if these changes are global and affect all players, if they are local only for a single player, either PC or Player State(in case other clients need to be aware that this actor has the altered variables)

that said you can have client specific altered vars in the GM and GS too, but you have to somehow index each player on login and so on

but this still has to go trough either GS,PC or PS for the UI to have access to their replicated version

[slender yarrow]

for the scoreboard i did do the game state with indexing. But for example in the UI for the Shop, I have a score variable that is changed based on what youve selected. Right now if you hit accept im sending that client sided variable into a server event on the player state which seems sketchy to me . I feel like it could just be changed/hacked in the UI and the server would get bad information

i cant figure a way around this with using a UI. Im having a total mind block

[high current]

yeah that way is sketchy, client should request stuff from the server, not set it

Also, only use player state if you want everyone to have access to the information at all times

As Player states are always relevant

[slender yarrow]

But i cant see how to do that with a UI. The UI is what needs to navigate everything. Unless youre not supposed to have ANY vars in the UI and always be making call sout to the GS or PS for information???

i guess that is how it has to be now that i think about it

[high current]

whatever info is gameplay dependent and part of the game mode and gameplay ruleset, should be calculated on GM and GS, and if clients need to have access to that, then it should be on replicated vars in the GS

Your UI can have variables to basically function, keep states, do animations and so on, but if it needs to fetch some important information that is gameplay related

it should cast to GS and be like `hey, is this information available for me, if yes ill get replicated variable, if no ill tell the server to get it for me and then get the replicated variable

or something like that

I don't know your specific case so I am making this up...

[slender yarrow]

Ok i think i get it. Ill poke around so more. Thanks for the help! ✌

[solar stirrup]

Is there a way to get a component's network id or something of the sort?

found GetUniqueID()

close enough

[timid moss]

Im not sure. that function seams to be the correct one though

[timid moss]

Hi. I am a little confused on how replicated TArrays work and their OnRep functions. Currently I have a Replicated TArray of Weapons that has an OnRep function associated with it. The server fills the Inventory TArray with weapons on character spawn so that you get your default loadout. So correct me if I am wrong but in this case shouldn't the Inventory only replicate once? Using a PrintString in the OnRep_Inventory() function, I find that the Inventory does only replicate once. But where my confusion starts is that sometimes the inventory gets replicated twice. I did some more debugging with PrintStrings in the OnRep_Inventory() function so that every time the inventory gets replicated it prints the contents of the Inventory, and I found that sometimes the TArray contains a NULL value in one of the slots, and when it does, it replicates the inventory again and that fixes the NULL value in that slot. Is this normal behavior with TArrays?

[fleet raven]

that is normal

use fast array serializer instead for an inventory

[timid moss]

Oh interesting. If you don't mind me asking why does a slot become null sometimes? @fleet raven

[fleet raven]

the array replicated before the weapon, so it set up the size, but could not resolve the reference on the client yet

[timid moss]

OHhhhhh. thx so much. ive been stuck on why this is happening forever lol

also for fast array serializer, is that this?https://docs.unrealengine.com/en-US/API/Runtime/Engine/Engine/FFastArraySerializer/index.html

kind of confused what fast array serializer does

[worthy perch]

Look in NetSerializer.h.

[timid moss]

Ok. Thx

[grizzled stirrup]

Since properties only replicate when they change, is there any overhead to having a property that replicates without condition but only gets set at the start of a match and doesn't otherwise change vs using COND_InitialOnly ?

[fleet raven]

yes, the property must be regularly compared to detect if it should replicate again

[grizzled stirrup]

Ok thanks will see if I can get away with InitialOnly

In the definition of InitialOnly This property will only attempt to send on the initial bunch if they mean the first time it gets set to a value other than default and replicates as initial bunch then it should be good

[timid moss]

@worthy perch how do I get to NetSerializer.h?

[worthy perch]

Sorry, I meant NetSerialization.h.

[timid moss]

oh thx

Also whenever they use the word serialize what do they mean by that?

[timid moss]

Hi guys. If the current actor is owned by the player and I am trying to do an authority check, is this enough....if (Role == ROLE_Authority)or do I need to do thisif (GetOwner()->Role == ROLE_Authority)

The actor owned in this case is a weapon

[hollow breach]

My Game is played via Lan for testing. Now hosted the game on mac-book(Mojave) but find session is not showing any results because of IPV6 sockets used by iOS i guess.

Is there any solution for this issue?

Warning: GetAddressInfo failed to resolve host with error SE_HOST_NOT_FOUND

Unreal editor 4.22.3 I'm using

[chrome bay]

@grizzled stirrup it means it will be sent with the opening of the connection and never again (i.e. when the actor is spawned or client joins), so if it's the default value it'll stay the default value. You need to set the property to what you need in PostInitComponents or somwhere early, possibly BeginPlay but I'm not sure if BeginPlay is early enough.

[upper tendon]

Hey, I have a problem, whenever I'm trying to cause damage to a player, I can only damage the client, but the client can't damage the host. Anyone know how to fix it? Thanks.

[bitter oriole]

Well, where does your damage code runs ?

Server or client ?

[upper tendon]

I use the "event Hit" in the projectile blueprint

[bitter oriole]

Okay, so where does the code doing hits runs ?

[upper tendon]

and I use "event anydamage" inside the character bp.

[bitter oriole]

The point is that most stuff should run on the server

If you call an event on your client, fine, but the server doesn't know

You need a RPC to also fire your weapon on server

[upper tendon]

you're right, let me have a look

you're right, the projectile doesn't even runs on the server and the other client

thanks.

[bitter oriole]

Deciding what runs on which is going to be a lot of your multiplayer code

Weapons in particular

[upper tendon]

Another question - does the function "Apply Damage" runs on the server? do I have to replicate it as well?

[bitter oriole]

It shouldn't run on other machines silently

If you call it from the server, it runs there and only there, etc

[upper tendon]

so, do I need to replicate it manually? I don't know about replicating manually in the projectile bp

[bitter oriole]

It's impossible to answer that easily. If you want the damage code to run on server, then you need the code calling Apply Damage to be on server

That can be your projectile doing this only in the server code, on hit

[upper tendon]

it says it runs on the server

[bitter oriole]

It says it only runs there

[upper tendon]

which means it doesn't run on other clients?

[bitter oriole]

Yeah, though it doesn't mean calling it from a client will call it on the server

You might want to look more into multiplayer tutorials and examples

This stuff is highly subtle

[upper tendon]

yeah

I've managed to replicate the projectile itself, so I don't think there should be any problem replicating the damage at the same way

[worthy perch]

If I RPC this struct:

USTRUCT()
struct MyStruct {
    UPROPERTY()
    float MyUPropertyFloat;
    
    float MyFloat2, MyFloat3;
}

Would the byte size of the struct when sent over the network essentially be the size of 1 float, or of 3 even though only 1 is marked UPROPERTY?

[thin stratus]

Does anyone have some info on Struct and Array replication in UE4:

• Does a change of a Struct member replicate the whole struct or only the changed property?
• Does the same count for Arrays?
• Does changing the size of an array also replicate the whole array or does it only replicate the change?

@worthy perch The UPROPERTY should technically only be needed for UPROPERTY(Replicated) marked structs of that type.

So if you actively send this via an RPC, it might send all 3 values, but that's something you could check

[worthy perch]

Does a change of a Struct member replicated the whole struct or only the change?
I have heard both sides from credible people on this Discord, but I think most people agree that the only the change is sent. (which seems like magic to me).

I think the whole array gets sent on change, otherwise there wouldn't be much of a point for FFastArraySerializer.

[thin stratus]

I read both for Arrays too

But I would also assume the whole arrays is sent

For structs I read it was changed in UE4 to only replicate changed properties

I do know you could check https://github.com/EpicGames/UnrealEngine/blob/release/Engine/Source/Runtime/Engine/Private/RepLayout.cpp

But I have a hard time understanding what I'm looking at

[worthy perch]

If you can't find anyone to answer those questions, you can take a look back at this section An Overview of Net Serialization and how this all works of NetSerialization.h. It's slightly too vague for me, but still decently valuable.
Generic Delta Replication part talks specifically about Arrays and Structs, but I'm still not sure if that means the whole thing is sent or not...

[thin stratus]

It heavily sounds like they added the ability to only send the "delta" state to the client

So basically the whole thing produces Delta and Full States of Struct and Arrays.

And sends the DeltaState to the Clients and keeps the FullState for the next time it compares.

That's for "Dynamic"Properties, so Structs and Arrays

Sounds good, thanks @worthy perch

https://i.imgur.com/1v3B4HQ.png

Tight call.

[plush mist]

Is it possible to tweak detour crowd to avoid jittering when AI Pawn wants tomake detour move around other AI? I used detour crowd controller and AI avoiding is nice , but jittering is so anoying...

[grizzled stirrup]

@thin stratus That's awesome! So if you had 10 properties in a replicated struct and only one got changed, only that property would replicate down?

[thin stratus]

That is what everyone hopes for

[grizzled stirrup]

Very nice!

[twin juniper]

How to replicate spawnemitteratlocation for all ?

[thin stratus]

With a Multicast at best

A non-reliable

[grizzled stirrup]

Or potentially a RepNotify FVector_NetQuantize but I'm not sure if that's more expensive than a multicast and you have to also ensure it's cleared for clients that come into relevancy later

Or in the case where that emitter is always going to spawn at a known location such as at the muzzle of a gun, you can simply use a RepNotify int

[chrome bay]

USTRUCT() does delta/per-property replication by default (for a standard member variable of the type) - unless you override NetSerialize, in which case it sends whatever you serialize

Arrays I'm not so sure, also not sure what happens to structs when inside arrays

[twin juniper]

Will Try these methods ! Thanks a lot

[chrome bay]

The extended explanation for structs is they do build an FRepLayout for the property in the networking layer and compare struct properties individually

[thin stratus]

@chrome bay That's what I understood too

Despite Arrays in Structs and Structs in Arrays

That seems to always cause full replication

[chrome bay]

Yeah I think that's true

Arrays are just sent as a big long bitstream IIRC.. per-item serialization would be kinda hard to do I would think without some custom implementation like the fast serializer

[thin stratus]

But isn't that what was outlined in the netSerialize comment?

That they do NetDeltaSerialize for arrays?

That only sends the delta state to clients?

@chrome bay

[chrome bay]

Ah good Q, I'm not sure

It would be nice if they did that's for sure

I'll have a proper look at some point.. would be nice to know

[cinder quartz]

How do you guys replicate hit effects when your weapon does multiple hits, like shotgun? I have random cone spread, so I guess I should just replicate starting location and seed for random and let clients roll their own calculation ?

[grizzled stirrup]

@cinder quartz I have an OnRep centralized ImpactLoc FVector that is used to determine the direction then the local clients do their own version of the shot but it is inaccurate

The seed idea is a good idea if you want the same spread response

You shouldn't need to replicate StartingLocation as it'd always be on the weapon right?

Otherwise the shots might come from somewhere else

[cinder quartz]

true, hmm, right now I'm replicating location and what I hit (enum to toggle blood or sparks etc) so even with lag client always knows what he hit, but I think this might be too traffic heavy for multihit weapons because it means for shotguns I actually need to replicate array of structs

[grizzled stirrup]

Yeah it gets way too expensive

Generally I find it's fine to do the what he hit FX locally and confirm damage on the server via a hitmarker or something

Many games take this approach and for almost all cases it looks correct

You can also spawn an additional blood FX on confirmed hit too

So 99% of the shots won't waste bandwidth figuring out if concrete was hit but when a player is hit, the blood effect will always play

It's a tricky mix of bandwidth and accuracy though

[cinder quartz]

yeah, will try the same random seed on everyone, it should be pretty good, or just take off the random spread and always do fixed spread

[grizzled stirrup]

Yeah honestly with even random spread, in any kind of fast paced game, once you see other clients shooting a shotgun, the illusion is good enough

Players generally won't be able to keep track of exactly where each shot went anyway

And as long as damage is clearly telegraphed, it should all make sense to them

Unless you are doing a much slower pace game where every shot counts, then it might be worth doing more specialized replicated hits

[cinder quartz]

yeah, gotta test some things and see whats best

another thing I'm thinking to reduce lag, would it be any sense to when client shoots, if he hits actor(enemy), to tell server the actor* and bone name, so server can check if it can hit that. That way even with high ping if you hit fast moving enemy on the head, it would most of the time count as headshot

[grizzled stirrup]

That's generally how it's done for most games to favor responsiveness

Client says he shot X

Server verifies

If it's within reasonable limits, the shot is allowed

[cinder quartz]

right now I'm just telling server the location as vector, so it can easily miss if enemy moves fast

[grizzled stirrup]

Generally you'd see if you hit the enemy clientside and if so tell the server about it, then do some kind of verification on the server

Otherwise it'll lead to clients missing shots they should have hit due to latency and being frustrated

[cinder quartz]

yeah im already seeing that

[grizzled stirrup]

More sophisticated approaches to verify can reduce cheating such as a full lag compensation rewind / retrace but start with a basic verification first

Reference ShooterGame

[cinder quartz]

but my "hit effects" come from server, so even now If i hit head client side, but server doesnt, I still see no blood, but theres a slight delay on hit effects

[grizzled stirrup]

Yeah that's why it can be a good idea to never spawn blood or damage effects clientside and always have them come from the server's confirmed hits

[cinder quartz]

I tried shooter game while simulating lag and it's bit funny, current clip ammo seems to work bit wonky, if you simulate high lag your current ammo will go to minus lol

[grizzled stirrup]

Might just be the UI being funky and missing an initial binding or something

Strange!

[cinder quartz]

yeah, not sure if it actually also shoots server side in that situation

do you have any idea whats accetable KB/s when profiling networked game lets say co-op game with 4 players, I'm having hard time figuring whats good data/per second

at least the regular limit seems to be 10 KB/s if you dont modify it

seems to be CMC doing most traffic anyway

[grizzled stirrup]

@cinder quartz 10 KB/s is definitely very low for todays standards

I've lifted the limit for my own co-op game as with several AI and lots of weapon fire it was quickly meeting the limit

[cinder quartz]

I lifted it to 20KB/s and its enough.. for now, guess I shouldn't worry about that now in prototype phase

[grizzled stirrup]

If passing in an options string that was previously only "listen", would it be formatted like so? "listen?MinPlayers=2?MaxPlayers=4" ?

[chrome bay]

IIRC the ? has to be before each option

So "?listen?somethingelse=2"

[grizzled stirrup]

Thanks a lot!

[solar stirrup]

Does the engine give anything for lag compensation? Or do I have to write it myself

[chrome bay]

Yourself

Pretty much impossible to write a "generic" one size fits all lag comp system

[solar stirrup]

Ouchie ouch

It's for a melee combat system too 😓

[chrome bay]

Gameplay Abilities has some implementations for prediction and such, but it's a huge system and you pretty much have to adopt it for the entire project to use it properly

[grizzled stirrup]

Is StartPlay() the best place to parse option strings?

Or can I be doing it earlier like PostInitComponents?

[chrome bay]

InitGame() is the place IIRC

It's called mega-early

[brittle karma]

guys any links or tips or codes about learning authoritative server client side prediction?

there is no tutorial at all for that, so how did u learn?

[bitter oriole]

There's one tutorial on Udemy

https://www.udemy.com/course/unrealmultiplayer/

Get it when it's at $10

[brittle karma]

well there is a problem with this tutorial i guess

it doesnt cover physics engine basically, he wrote the movement from scratch

[bitter oriole]

Yes

You need to do this

UE4 uses PhysX which isn't deterministic, so you can't have prediction based on it

Multiplayer physics is really hard even with a better physics engine, too

[brittle karma]

alright then

https://www.youtube.com/watch?v=CAWwut4hSPA

@bitter oriole this says Client-Side-Prediction with Physx

[bitter oriole]

Yeah and you can see visual rollbacks every second on flat terrain without other players

[chrome bay]

I've seen enough "WIP" videos of PhysX prediction to last me a lifetime

None of these ever end up finished you notice 😄

[brittle karma]

is this problem only exist on none characters or CMC has this problem as well?

[chrome bay]

CMC doesn't have the problem, but it's not using PhysX

[cinder quartz]

"Networking is fully implemented, with server-client correction and prediction included." says in the CMC doc

[chrome bay]

CMC works fine on the network because it's completely kinematic and Epic have an insanely complex chunk of code making it happen.

But it's a very bespoke solution that works for characters and not much else.

Physics simulations massively increase the complexity of the problem. It's been an unsolvable problem in games since the 90's

[bitter oriole]

CMC simply does not use physics simulation at all

[chrome bay]

Don't feel bad about not solving it

[grizzled stirrup]

Didn't Rocket League have to make their own physics solution or something?

Seems like a very difficult problem to solve

[chrome bay]

Yeah, it's clever what they did but it's a very bespoke solution that is tailored for their game

Wouldn't scale past 8 players or to anything crazy complex

[bitter oriole]

Sea of Thieves also has a custom movement component for ships

[grizzled stirrup]

Rocket League is like the ideal game in so many ways- small limited map, few players and not much to render / replicate

[bitter oriole]

You can see how it behaves it a very un-physical way by crashing the ship into an island and watch it retrace its steps backwards

[brittle karma]

i couldnt recognize how hard can it be XD

[bitter oriole]

It's simple

Same data in, different result out

So you can't predict what the other player does on his machine

[chrome bay]

Yeah I used kinematic movement for my vehicles for ages, which worked really well until I wanted something with wheels or in constant contact with a surface, or remotely realistic collisions

Then it all went to pot

collision r hard

[grizzled stirrup]

They probably have a custom movement component for vehicles in Fortnite too right?

The quads are crazy

You can go very fast and go all over the place

[chrome bay]

They use client-auth physics in fortnite

[grizzled stirrup]

Ohh that's interesting

[chrome bay]

they just went hard on anti-cheat

[grizzled stirrup]

So technically you are telling the server where you are and it interpolates your position to everyone else?

Similar to using client side auth on the CMC?

[chrome bay]

Basically yeah, client tells server where it is, server accepts it (checking for obvious cheats I imagine) and pushes that out to clients

The simulation is running for all players constantly so physics naturally smooths out a lot of the motion

[grizzled stirrup]

That's great, I was really wondering how they managed to pull off some situations with no jitter or corrections

[chrome bay]

But they have some custom interp behaviour as well (See FPhysicsReplication)

[grizzled stirrup]

Since even launching character at high speeds in vanilla UE4 with CMC causes a lot of corrections with latency

[brittle karma]

i myself wanted to have client-auth and it cost me sooo many strange collision stuff

[bitter oriole]

Client auth is way easier

Except for the massive anti-cheat required

[chrome bay]

Clients that are collidiing with each other will constantly screw up

There's nothing you can really do about that

Each client thinks they are in charge of the simulation so they're always going to be fighting with each other

Add latency and variable frame-time to the mix and you're screwed

TLDR don't bother making destruction derby simulator 2019

Unless you wanna cry a lot

[unreal pine]

Wreckfest?

[brittle karma]

even stranger, collision of components fall apart

[coral girder]

Oooor do your own networking and avoid ue4's replication, maybe use lockstep, but not sure how that'd fair for more realtime games. Hmm that or a full authorative server.

He's correct though physics are messy with p2p networking.

[brittle karma]

@chrome bay but if fortnite is using client side simulation how its possible with the problems u mentioned?

[coral girder]

How often do people bump into eachother?

I'm willing to bet if they do they jitter a lot.

[bitter oriole]

Months of work by large teams of extremely experienced UE4 engineers

That helps, too

[coral girder]

Probably not using their own engine the same way most would either is my guess.

[chrome bay]

Even character movement has issues when two characters from different clients walk into each other

[coral girder]

If you have the goals understood ahead of time you can get around all of the problems with enough hackery 😛

Yup that ^

[chrome bay]

You'll notice constant jitter while the clients try to resolve collisions independently then get yeeted somewhere else by a server correction

[coral girder]

Oof those suck.

[cinder quartz]

Yeah that happens in Dead by Daylight all the time, walk behind another player and you rubberband constantly

[chrome bay]

Two clients determining collision outcome is an unsolvable problem unless you're using deterministic lockstep

But nobody in their right mind is using DL anymore unless they're making an RTS or something

[coral girder]

^^^

Exactly

[chrome bay]

Too much input latency for a shooter etc.

[brittle karma]

so for clarifications, wheeled vehicles are sucky and there is no way to solve the problem?

[coral girder]

Dude it's hard stuff >.< And there's like no tools for that anyway.

No there is.

How many racing games are p2p?

[chrome bay]

Multiplayer physics is always going to be a compromise in some area

[cinder quartz]

Path of Exile uses lockstep and it works kinda good, but its not fast paces shooter, it can be fast paced tho

it's not UE4 either

you also feel input lag all the time

[coral girder]

Yeah I've never seen a lockstep game in ue4, there's no plugin for it and it'd require that you deal with the packets yourself, something I don't expect indie devs to do, would probably use their own engines.

[bitter oriole]

It's possible to have wheeled vehicles in multiplayer that don't suck. Two methods : use another engine (not Unity either) with Bullet physics ; or use client-side auth with a log of additional logic and processing

[coral girder]

^

The latter i'm willing to bet is what most do.

[brittle karma]

@bitter oriole do u think that udemy tutorial is good enough to solve it?

[bitter oriole]

Well the tutorial does server auth

[coral girder]

Networking is a complex beast >.< I'm a newb in it myself and it's hard to find what i'm looking for.

Server auth is a good way to start learning though is my guess.

[brittle karma]

@bitter oriole but no physics engine is involved

[coral girder]

Doing a simple game yourself from scratch like say internet pong teaches you a lot more than a prebuilt engine can.

There's two problems with physics engines, lag, and floating point math.