[MUD-Dev] The Lag monster...

[Miroslav Silovic]

Amanda Walker wrote:

> Lag is still a big problem.  We have enough bandwidth, enough
> processing power, and we don't rely on round trips to a big server
> in the sky, but lag (which we call by the highbrow term
> "guaranteed upper bound on communications latency") remains our
> single biggest technical issue.

Let'd do a little calculation here. Suppose you have 100 visible
objects, and send position updates 50 times per second. Homogenous
matrix in single precision is 4x4 floats, or 64 bytes. Since you
won't want to do scale, skew, or projective transformations, you're
down to 6 independant components for translation + rotation. This
gives you 4*4*4by * 100 * 50 = 120KB/sec. But even a crude lossy
compression will give you a huge ratio - most of those 100 objects
will not move quite /all/ the time, and you're allowed to nib a bit
here and there, and the components of these matrices can be pretty
accurately predicted from frame to frame. I'd say 1:20 is a
reasonable minimal ratio you can expect. At 1:20, this is
6kb/second. For 100 objects at 50 fps, without too many fancy
techniques.

I'd say network bandwidth is just simply irrelevant to lag. And
latency is nothing you can do anything about (beyond interpolation).

    Miro
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