Originally Posted by tjmonk15
This whole PhysX situation confuses the hell out of me.
I understand PhysX it self and what it does/implies. What I'm confused on is this: How can a client-side technology help with a authoritative-server MMO?
I mean, vehicles fish tailing, bullet drop, flight mechanics.... in an authoritative-server environment need to be server side.
Unless I'm missing something obvious?
The only thing I can think of is that they are using PhysX server-side for the physics, and then sending that data client side and the client-side PhysX will apply it to client-side entities. But then this cuts down on bandwidth severely.
So.... anyone have any insight?
-Monk
|
What generally happens in netcode is that both the client and server calculates all game important physics (physics that can actually affect gameplay), the client uses the result of the calculation to display the result to the user immediately so there is no latency involved with gameplay.
The server essentially does the same and sends each client periodic updates, the client looks at the new data and if the client disagrees with the server it corrects the necessary client side properties to match. If you're talking about the position of a vehicle for example then slight differences in position are resolved by the client moving from it's current position to the correct one using a Lerp (Linear interpolation) function, it basically smooths the current client side movement so you don't jerk around all over the place.
Some physics will not be important to gameplay such as ones that drive graphical effects and since these cannot effect other players they're not updated across the network.
Generally speaking a legit client should never differ from the server in any significant way, a client simulating the same variables comes to the same conclusion as the server. The only difference comes from other players interactions, the server gets these updates first and based on other players altering the battlefield may come to different conclusions than the client and it's under these circumstances the server corrects the client with the "real" information.