Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!dali.cs.montana.edu!milton!wex@dali.pws.bull.com From: wex@dali.pws.bull.com (Buckaroo Banzai) Newsgroups: sci.virtual-worlds Subject: Re: Who says what to whom (was Re: VR Protocols.) Message-ID: <8077@milton.u.washington.edu> Date: 24 Sep 90 17:13:10 GMT References: <31304@unix.cis.pitt.edu> <7507@milton.u.washington.edu> Sender: hlab@milton.u.washington.edu Organization: Bull Worldwide Information Systems Inc. Lines: 52 Approved: hitl@hardy.u.washington.edu In article <7986@milton.u.washington.edu> brucec%phoebus.phoebus.labs.tek.com@RE LAY.CS.NET (Bruce Cohen) writes: I like the idea of objectifying Space, but maybe the problem is having a unique Space object. Suppose instead that there are a number of them; in the limit, one for each "material" object (surely we can come up with some terminology to make talking about virtual objects easier!). Each Space object has some spatial locality to be concerned about, and has knowledge about and control over the geometry in that locality (incidentally making multiplex manifolds easy to implement). I like this idea - sort of like the way air traffic control is done today. I think it would work, but I'm not in a position to go off and implement a trial system :-( Whether or not Space objects are shared, no object should directly send messages to a Space object other than ones which are local to the position of the object (there might be more than one if the object was on the boundary between two localities). Right. There could even be a stylized "handoff" procedure, just as is done with aircraft in flight. I can see two problems - one theoretical, and one implementational. Theory first: The subdivision of space carries with it the implicit assumption that object have no effects outside their volume. This will break down if you get to forces that act over a significant distance (say, the effect of solar wind and gravity on an earth-moon flight). The implementational problem comes the first time you have an adhesive collision (say, ball into catcher's mitt) occurring at the boundary of two volumes. There will be *lots* of message-passing going on. This is not to say I've changed my mind - I think this idea is on the right track; I'm just pointing out things we should be careful of. While in this scheme there are probably more total messages than if there a single Space, there is a greater potential for parallelism, since we have, very literally, a great deal of locality of reference. Since VR worlds are likely to be highly ditributed, I think this is a win. I agree again. The more I think about it, the more I think I want a parallel language to do any kind of reasonable modeling. Unfortunately, I don't know squat about parallel programming :-( That's why I was hoping to sneak by with a parallel implementation of an object-oriented language I did know. -- --Alan Wexelblat phone: (508)294-7485 Bull Worldwide Information Systems internet: wex@pws.bull.com "Politics is Comedy plus Pretense."