Re: Coordinates and Multiuser

Peter J. McCann ([email protected])
Wed, 3 May 1995 22:27:48 -0500 (BLT)


Sean Riley writes:
> Could this virtual space be represented by something analagous to URLs?
>
> Objects within a server are referenced by a relative address - but objects
> anywhere in the "world" can be referenced by specifying the server and the
> address within the server.
>
> This way, a scene could be built up using objects that live in any number of
> servers - just as a Web page can be built using resources from anywhere on
> the WWW.
>
> In this case, when an object is "subscibed(?)" to by a browser, the server
> becomes "aware" of it and can send future updates when aspects of the object
> change.

This is an idea I've been playing with for a while now. One of the more
interesting ideas that has occurred to me is that someone's subscription
network (the set of all the services they subscribe to, along with the
services those services subscribe to) is a DAG with a good deal of
structure that might map nicely onto a VRML scene description. It would
be interesting to render these networks, using geometry to represent the
logical relationships among the elements, and look at the way different
people gather information. I might even want to construct an meta-index
(subscription service) of these information-retrieval structures.

> How can this possibly work with vrml? Hmm....
>
> To add maximum flexibility, clients should be able to "subscribe" at
> different levels. If they enter a room, suddenly they are subscribed to all
> the objects in the room. If they wish to import a complex virtual object
> from a room into a scene, they just subscribe to that object within the scene.
>
> Could this be done by attaching a list of subscribers to a seperator?
> The subscription woul dapply to all the objects "below" the seperator.
>
> This would give great flexibility - the ability to get updates on a sub-tree
> within an object hierachy.
>
> Also, servers could be browsers also - propagating objects throughout
> whatever virtual worlds people create.

I think the "portals" idea could be implemented fairly easily in this
kind of environment. I could subscribe to a service that sends me the
VRML file whenever it changes, or maybe just a single image of the scene
rendered from a single perspective that I could then texture-map onto my
portal polygon. If the server had better rendering software (or if updates
to the scene were infrequent) it could even send me a nice ray-traced image
of the scene (hehe, "the grass is always greener on the other side of
the portal").

> This could work in conjuction with an absolute co-ordinates system. There
> would be a distinction between a "real" object on its home server, and
> copies of it propagated to other servers.
>
> -----------------------------------------
> Will we see wars over who "owns" (0,0,0)? A HUGE Coke sign perhaps?

IMHO, the hard-coded coordinate system is a Bad Idea (tm). Aside from
imposing the need for central authority, I don't think we should limit
cyberspace to fit into our ideas of well-behaved geometry just because
it makes it easy to map out. Given the computational resources we have,
there are much better ways to index information than with geometry.
The index I use might not even be the same as yours. If we go with a
world-consistent geometry, then the logical relationships between VRML
documents that emerge later (after land has been parceled out) will not
be representable.

-- 
Pete McCann                                          [email protected]
Department of Computer Science           http://swarm.wustl.edu/~mccap/
Washington University in St. Louis