Hi all,

I don't have any experience in gaming industry and I would like to do some gamin development for fun (initially on server side).

However, being the noob I am, it is not quite clear to me what is generally considered a good approach in the industry in terms of the split of game logic between server and client regarding the geometry.

For example, let's assume use case from Counter Strike: flash bang is thrown. Target position of FB is X, and its impact radius is R. Then, the question is, who does calculation which players will be impacted: client(s) or server? Calculation would be "for every player's location(which is represented as point in geometry) within radius R of impact point, if there exists straight line (i.e. is visible) between player point and impact point, then apply flashbang effect" etc.

To me it seems that for every map, server side has to keep some kind of representation of map geometry (without graphics part) and player location in order to at least prevent cheats, and also to smooth out gameplay i.e. decide and enforce total event order across all clients (i.e. decide which player got the actual headshot first in case they click around the same time etc).

Thanks in advance for any input.

cheers!

You have to share some code on the client side and the server side.

You have to keep in mind all gameplay stuff has to be done on the server side.

When a gameplay state is updated you have to send a message to all client who is connected about the change.

You have to take care of the bandwidth, don't send information who is not needed and use timer for some state of transform.

About the flashbang it could be one message with ID FLASHBANG_LAUNCHED who just add the flashbang on server and send the ID on client.

Using this ID who is called NetworkID you can update object from server to client, Raknet has a replication system who handle all that.

You will have to handle the reconnection of client if you need to keep the game in state, for counter-strike state of player is not stored.

In a DOTA game, when you have a reconnection the player keep his position on the list and has kills/deaths stored.

Thanks on quick reply guys!

A typical approach would be that you have the collision/physics representation of the level geometry also on the server,

I checked Unity documentation but was not able to find low level technical API. Unity seems to me very client/graphics centric, without clear server side API.

Are there any open source or commercial libraries you would recommend to start with? I am looking for game-centric API similar to this one: http://tsusiatsoftware.net/jts/javadoc/index.html, but with support for 3D and ideally with built in game abstractions (i.e. calculate bullet trajectory etc)

thanks!

edit: it does not have to be Java library, any language is fine.

What kind of library are you looking for? If you're looking just for a network library, try RakNet? It's what Unity uses under the hood.

Unity is easier to get set up as client/peer, but it's not that hard to make it client/server. Though I haven't looked into how much work it would be to make it do a standalone server with no rendering.

My game logic split is basically:

Players send inputs to server (I pressed fire and I am trying to move forward)

Server computes game logic and sends results/events to players (player X is at position XYZ, facing north, spawn a rocket at time T, etc)

Now, that works okay in a low lag environment, in a high lag environment, it's better to simulate the results of the input on the client, and then interpolate/fudge things to sync up with what actually happened on the server.

And in an RTS, things are usually done differently.

What kind of library are you looking for?

Some kind of library/framework/product which offers API & implementation of common 3D geometry algos.

Server computes game logic and sends results/events to players (player X is at position XYZ, facing north, spawn a rocket at time T, etc)

How to compute logic in your example is what I'm looking for (i.e. if trajectory of my bullet is line L, compute if head of any enemy is intersecting with that line, and similar to other situations, such as non-streaight line ammo in unreal tournaments Flak Cannon etc).

Since I ain't expert in geometry, don't want to spend time writing that first. =)

edit: the java library i posted earlier has almost the needed functionality except it is in 2D and has no abstractions for gaming.

So you basically want a math/physics library? Try bullet? The server in a client-server game is pretty much running the game itself. Sure it's not rendering, but it's pretty much doing everything else, and then some, so, what you really need is a game engine with networking components.

Ok, thank you all. I think I understand little bit better how things work (bullet seems to be good starting point).

Thanks for tolerating my noobness. =)

a good thing too since the game was totally non-deterministic, and therefore has to transmit combat results, etc, not just moves and input. since the title was non-deterministic, prediction methods were not an option - and would have been unacceptable due to the accuracy required by the simulation - IE no being denied a kill due to inaccurate prediction methods.

So this is a slight derail, but metamorph seems to have gotten a lot of good info, and might also find it useful. Would you mind expanding on what you were doing that was non-deterministic?