[sldev] history question: physics on the server- first for SL ?

Ricky kf6kjg at gmail.com
Sat Mar 7 21:37:00 PST 2009


Running physics client-side is asking for packet-hackers to cheat.  Running
it only on the server invites physics lag.

Because of this dichotomy, most /games/ run most of the processing
client-side, with server-side checks to try and catch cheaters. (Or so I
understand..) This leads to an arms race... Expensive.

SL was designed as an community cooperation and construction environment.
(Again, or so I understand.)  this makes the possibility of slight physics
lag acceptable, as twitch skillz aren't needed.

To me as a beginning software engineer who has studied a little into
networking, I prefer all the physics being computed server-side.  Less
worries about cheaters.

Yet there can still be issues.  Ever played Halo online? Notice how that,
unless you're host, you have to lead everybody by a bit more than normal?
And that the distance you have to lead by is related to your ping to the
host?  In Halo, one of the clients is chosen as host.  That lucky person
gets to see everything in real-time.  Everyone else sends shoot requests to
the host and it processes them when it gets them.  Sometimes up to 100+
milliseconds later.  Whoops, miss.  Now, note: I've never played Halo
myself, but I've talked with many who have, and I hear this issue commonly.

Another issue than cheating shows up if a game allows the clients to do ALL
the physics.  On my machine, I shoot and just barely head shot you, but on
your machine, you just saw me and ducked behind a pillar in that 100ms of
ping delay... Which computer is right?  How do you programmatically choose?
To me, I killed you.  I even saw the bullet hit! But to you, you were
nowhere near that bullet.  Ugh.  Wars have started over less....

Hopefully this mess clarifies things :D
Cron Stardust.

On Sat, Mar 7, 2009 at 9:18 PM, SignpostMarv Martin <me at signpostmarv.name>wrote:

> A question thats been bugging me lately: Was SL the first major (or ever)
> virtual world environment/mmo to simulate physics almost entirely on the
> server ?
>
>
> ~ Marv.
>
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