From: broehl@sunee.waterloo.edu (Bernie Roehl)
Subject: Re: TECH: My standard is better than your standard.
Originator: hlab@milton.u.washington.edu
Organization: University of Waterloo
Date: Tue, 21 Jul 1992 14:12:15 GMT



In article <1992Jul19.055422.12836@u.washington.edu> Jeremy Lee
<s047@sand.sics.bu.oz.au> writes:

>I've got an answer to this. See my report. Objects themselves decide
>which other objects to talk to. Objects naturally form a group that
>talk almost exclusivley to each other, and that, to all intents and
>purposes, is the same as a "world"

I really like the sound of this, if it can be implemented efficiently.
How do you deal with the... wait, I should read your paper first before
asking a lot of questions that you may already have answered.

>>If an object is to be invisible to certain other objects, it simply
>>doesn't acknowledge messages from that object (including messages like
>>"what do you look like" or "what is your location").
>Heyyyy! We think alike. I came up with exactly the same thing last
>night.. Each object is responsible for only itself.

Exactly.

>>However, I still have to worry about all the stuff in the office next
>>to mine.
>
>Probably the best way to deal with this is to use a system where if an
>object doesn't get seen for one frame, then the chance of even
>attempting to render it for the next frame goes down.

A good idea, but what do I do when I first enter the world?  Do I have
a long start-up period while I receive and render the entire environment?
(Also, some graphics implementations will find it easy to keep track of
which objects are actually visible; others will find this very expensive
to do).

>I agree. It's easier to put the messages in a queue, with timestamp
>attached. If the object want to pay attention to the timestamp, then
>that is their business.

Right.  (Of course, sending a timestamp with every single message does
add to the overhead and lowers the performance).

>The universe itself throws causuality out the window on occasions
>anyway, so why worry about that?

Agreed.

>You can't rewind it. It's a non-deterministic system.

Agreed again.

>I personally like the idea of 128 bit numbers to describe spatial
>co-ordinates.

I still maintain that 128 bits is overkill.  How often do you need to
model the entire universe at the quantum level?  And having all that
extra data to send around the network would degrade performance even
further.  I think we should start with something smaller, but that from
day one we should make provision for expansion.

>>>Extensiblity is a requirement for any protocol.
>>
>>Agreed!!!
>
>Of course.

I think this is one of the points we *all* agree on!

>Routing and all network stuff should be trasnparent and should have no
>bearing on what constitutes a world. In that sentence, you are basically
>saying that objects are restricted to worlds in close physical
>proximity, and I therefore wouldn't be able to connect to a world that's
>in Tokyo, for example.

Not sure what you mean by "a world that's in Tokyo"?  A virtual world doesn't
really *have* a physical location.

As to why routers are important... even with very, very high-bandwidth
networks I don't think we want every object in the multiverse having to
broadcast to every other object.  We need some way of limiting traffic
to those who are interested in it.  (Broadband vs baseband, sort of).
Different "worlds" (and perhaps different regions within a world) are
different "channels".

>Sounds like your routers are central controllers, and I thought we all
>agreed that they just won't be able to cope.

Not central controllers; *distributed* controllers.  Even "controllers" is
the wrong word.  They're routers; they help objects communicate efficiently.

>See my paper.
>[...]
>See my paper.
>[...]
>See my paper.
>[...etc...]

All right, I get the idea.  You want me to see your paper, right?  :-)
Looking forward to it.

-- 
        Bernie Roehl, University of Waterloo Electrical Engineering Dept
        Mail: broehl@sunee.waterloo.edu OR broehl@sunee.UWaterloo.ca
        BangPath: uunet!watmath!sunee!broehl
        Voice:  (519) 885-1211 x 2607 [work]