collision on non-authoritative server (discussion)

Unity Engine
1

Hello,

I am using PUN for my multiplayer game involving ships. Where i am currently hanging is at the collision. I want the ships to be able to ram each other, getting damage according to there speed and also bouncing away a little according to there physic material. Unfortunatly Photon game servers are non-authoritative so i need to make the calculation with the clients somehow.

I know there is no perfect solution for it and i am aware that the goals i wrote before may not be completely reachable. This thread should be a discussion about finding the next best thing. About what i actually CAN do to give every player a smooth game and collision feeling (does not really matter i with PUN or Unitiy Networking i guess).

Anyone any suggestions what can be done?

2

yup, those are the cons when using photon, specially PUN, which runs in the cloud there is nothing you can do about it when it comes to collisions, you pretty much end up with an authoritative client side since photon cloud is just a relay between 2 clients.

so no, you cant do server side collisions, period, you can do mumbo jombo checks but at the end of the day you still in an non authoritative environment and therefore cheats will be all over your game.

so do yourself a favor , if you want a fully authoritative server just go for uLink and save lots of time by going other route. it is not worth the time to invest doing such a trick in other networking alternatives.
photon cloud is just for very casual and simple minigames, where there is no need of an authoritative setup.

3

The problem is i already written a lot of code using PUN. How much work is it to “switch”? Where do i find informations and prices?

4

Unfortunatly Photon game servers are non-authoritative so i need to make the calculation with the clients somehow.

Assert that one of your clients is the ‘authoritative server’.

5

I just found out that uLink costs €660.00 since that is A LOT of money i am not ready to buy this hoping for the best. Is there any way sto start imlementing and test stuff with there sytem and only buy before the game comes actually out? Also it does not tell me if i need Unity Pro (wich i dont have or intent to buy).

6

About Authority

I might be biased but I think people make security a bigger problem than it must be. Especially in the beginning. Try to get your game working and find some audience.

While authoritative clients mean some extra work, authoritative servers just cause a different type of work.

If your servers are authoritative, then you better keep them up to date when you update any level. Maybe you even need to do a simpler version of your 3d assets to keep CPU-usage low. Expensive CPUs are usually a no-go for F2P or cheap indie games that don’t have subscriptions.

If you can live with “authoritative” clients or not depends on the game and your ambitions. If money is involved, you have a lower tolerance for issues than when the game is a hobby project.

You should start with basic sanity checks that run on all clients. Track the usual issues you will get: Speed hack, perfect hit ratio, etc. If some player is suspicious for more than one client in a short time, then kick that player.
You will need accounts soon after that. If you kick one player, that’s only half of the story, cause that user can simply join another game, right? So you need accounts and ways to pause those or ban them permanently.

Photon Cloud does not have accounts built-in but it has “Custom Authentication” and “Web Hooks”. These two pieces allow you to setup a web service which can modify the accounts and ban users.

About Physics

Photon Cloud does not do “Unity physics”. If that’s a big problem for you, you will have to pick another solution.
As said: Physics on the server will cost you and can cause other issues. Also, having it on the server is not a guarantee that lag is no issue at all. You usually still need some lag compensation.

Having 2 ships collide and push each other around physically-correct is a little challenge. All clients will simulate the situation locally but no matter how low the lag, both clients might move the other’s ship in another direction. They don’t have the same result automatcially.
Server side physics might help here. For the worst case of “some more lag” you will need to be able to reset the positions, despite the server being right.

I am not the best to give tips about how exactly you should implement your ships. I simply didn’t experiment with that a lot.
Try to look up lag hiding algorithms and experiment with your case. As it’s the core of your game, invest a little time.
Or: Let the ships pass each other. Just do collision detection for the shots. Let the shooting player decide if it’s a hit and the others can check if it makes sense or not at all.

Sorry for the long-ish post and that I can’t help with concrete examples.