[sldev] movement within the client

[Callum Lerwick]

On Sat, 2007-12-29 at 18:34 -0700, Lawson English wrote:

> Thanks for the info. Rather than workarounds, I'd rather that we asked 
> for new features though. This isn't supposed to be a competition to see 
> who can hack the server the best: its supposed to be a collaborative 
> effort to see this thing thrive, or such is my attitude.

Yes, the way movement is handled now is pretty crackrocky. Under laggy
conditions, and especially under low framerates, which basically means
always in popular areas, it becomes impossible to move without
overshooting all over the place, rudely plowing through people and
falling off platforms.

There's basically three things I want to see:

1) No overshooting
2) Proportional control (such as with a joystick)
3) A "move to here" option

I can't say I know what I'm doing as far as low level protocol design
for this, but my guess is this all could be accomplished with a "I want
to be at X,Y,Z" client-to-sim message. The sim would still be
authoritative about avatar position, it should be viewed as a request,
the sim could ignore or modify the actual result as it sees fit, such as
collisions, bounding avatar velocity, etc. Which is pretty much what it
is doing already.

This would prevent overshooting, since the message is an absolute, not
relative. This would allow proportional control, the client would just
be sending a series of short X,Y,Z updates.

SL actually already has a "move here" feature, but it only works on
terrain, so unless you're in a sandbox it is pretty much useless.

(And of course we can and should always ask the question, "How does
Quake 1/2/3, Doom3, HL 1/2, Unreal etc etc game engines handle this?",
they've been doing this for years... AFAIK a major difference is they
all perform collisions/physics simultaneously on the client and server,
and resolve any de-synchronization by holding the server authoritative.)
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