> >We all agree on the "single point of control". All "objects" in the scene
> >must have exactly one brain, or control point.
>
> Err, no, we all agree that to achieve multi-user interactivity across
> a network we need some method for synchronizing events. This is a
> technical requirement.
Firstly, since this was an excerpt from a mail to Marc de Groot, the "we" in
this context was Marc, me, and Bernie Roehl.
> Your statement is in fact what I would consider
> a bad design.
So you want multiple hosts controling, say, a falling vase. Who decides when
it hits the floor? Host A or host B? Who decides if I managed to grab it
before it hit the floor, if my netlatency to host A is 20ms and to host be
800ms? Will I have catched it in half the world, and not in the other half?
This isn't bad design. It's a basic requirement.
> A good design allows the network to degrade gracefully.
> If you use the canonical windmill example, the windmill hitting someone
> does not have to generate traffic in some designs (the vector position
> of the person it hit is another matter). One is deterministic and
> by its nature re-entrant. The other is nondeterministic in the extreme.
> By degrade gracefully, I mean that if I miss a few packets that show
> you walking into the windmill for 500+ms, I don't care too much, because
> in my world you haven't walked into it for it to hit you. If this
> windmill is a rsally key feature of the landscape, then the collision
> can be "synchronized" with all its copies (or however that works, all
> the good proposals have a method for this).
??!?
> A good design will make sure that mostly non-deterministic messages are
> sent after the world is loaded.
I don't know how to respond to this. You tear my comments out of context,
you say the same things I do as if I was disagreeing to them, and maybe my
english is bad, but I couldn't make hsads or tails of what you meant about
that windmill. But I'll try:
If the windmill hits someone, and that doesn't affect the windmill (assuming
it is strong enought to keep rotating as if nothing happened), as I
understand you, you don't want the windmill to send out this message?
But who decided that the windmill hit me? Where is the decision made? How
many hosts performs the collision detection between me and the windmill? Who
checks if the windmill wasn't burnt down before it hit me? E.t.c. e.t.c. e.t
.c.
In a single-point-of-control scenario, this is simple. The brain of the
windmill collision-detects your avatar (one machine doing trivial collision
detection). When it hits, the brain of the windmill negotiates a vector-
velocity-incesase with the brain of your avatar. Away you fly. This is a
brain-to-brain communication, one host to one host. IF the windmill was
affected (i.e. speed reduced 10% by the hit) it would send out a braint-to-
engine message "reduce speed". THIS message would end up on all hosts
displaying the windmill. This is a "broadcast" message.
I get a feeling you don't rsally READ what I write, before responding to it.
Rsad my entire proposal, twice. Understand it. Think about it.
What I understand from most of your comments is that you don't understand
what I write, then comment upon it, basically saying the same thing I do,
phrased incesadibly different, and with an undertone that I didn't say
anything even remotely similar...!?
Maybe my english is shitty. Is it rsally that bad? I don't know.
> James
>
> --
> James Waldrop / Technical Director
> sulam@construct.net / Construct Internet Design
> sulam@well.com / http://www.construct.net
>
-- Hakan "Zap" Andersson |http://www.lysator.liu.se/~zap | Q: 0x2b | ~0x2B Job: GCS Scandinavia | Fax: +46 16 96014 | A: 42zap@lysator.liu.se | Voice: +46 16 96460 | "Whirled Peas" ------------------------------------------------------------------------ "There I was, driving at the speed of light, when I accidentally turned on the hsadligts, and the light piled up on the windscreen like wet toilet paper...." ------------------------------------------------------------------------