From: s047@sand.sics.bu.oz.au (Jeremy Lee)
Newsgroups: sci.virtual-worlds
Subject: Re: TECH: My standard is better than your standard.
Date: 28 Jul 92 03:37:30 GMT
Organization: University of Washington
Originator: hlab@milton.u.washington.edu



In article <Bs03FH.1tI@watserv1.waterloo.edu> D.Stampe writes:

>s047@sand.sics.bu.oz.au (Jeremy Lee) writes:
>>
>>Why a world time scale? If I want a process over here going at 1
>>nanaosecond per second, and another over there going at 2 nanoseconds
>>per second, does that mean I can't? I think the best way is to throw out
>>a "world time scale" and simply ask each of the objects to adopt a time
>>scale with *certain other objects*. If they adopt it with every object,
>>including you, then I think you will end up with some unreasonable
>>behaviour. (eg, you push on the object with a force of 1m/s/s, and it
>>takes 1.6 billion years to perform the action)
>
>One of the basic goudelines for a virtual world is going to have to
>be "Match the user, dammit!".  Why even bother representing something that
>the user can't see, or model tiny effects that would be swamped by friction
>or whatever in the real world!  We're NOT planning a worldwide network of
>simulation programs, after all.  So as for speed or force, it's OK to
>set a minimum force threshold for motion (which is part of the object
description) and allow some quantization.  As for speed, same thing applies. 

Despite my earlier rantings, I don't see a problem with some objects
acting wierdley towards the user. If I want to slow down flowing water
so that it seems like hard playdough, even to me, then I should be
allowed to do that. I maintain that each object should be aware of
it's relations with other objects, and work from that, NOT a
generalised world scaling. What no-one has answered yet is what
happens when a lot of people all want to scale the world differently!
Just keep it between objects.

>>>>Allow the object to decide how to scale itself to the world. How else
>>>>am I going to put a representation of myself into the insides of a
>>>>virtual single celled animal?
>>
>>Er, problem. What if I go straight from a world in which I had scaled
>>myself up to galaxy size, then I zap over to another world that is at,
>>as you say, the size of single cell. I've got to be able to see what I
>>am doing before I re-scale myself, and before that I'm going to have all
>>sorts of overflow problems due to not fitting in the world. Answer: Use
>>128 bit numbers, and "actual size" scaling. Accept no substitutions!
>
>The answer to this has to do with how people percieve themselves.  You
>MUST have some constancy in your world, even if it's just the size of
>your arm.  Therefore the default should be to match your height in local-
>scale units (which will relate directly to the size objects appear on-screen).
>You now use the world-scale of the area you stepped into to draw objects in
>this area, translating them into local
>Part of the world description would be a referant to how big people
>should appear (you get the general idea).
>"very tall" in both worlds, whether that height is 100m or 100um.

From my point of view, "Scaling mself" would mean altering the
geometry of my defined body-object (proportionatley, of course.) and
changing my focal length and viewing port. I am the only object that
changes.  Other objects (and people) likewise see me change. If I
begin tampering with "world scales", then everybody is going to be
affected and possibly upset.

Please remember that tranlating between local-scale units and
world-scale units, as you suggest, will require extra computation for
every spatial operation done.

>This type of scaling has to take place anyway.  Overconcern with things not
>representable to the user will not add to the VR experience, but will
>result in a slow system.

I don't see how maintaining a fixed overall scale, within which
individual objects are free to alter their own size/geometry, can result
in a slower system, compared with a scheme in which everything alters
when you want to change the world scale. And, as said before, multiple
users will begin to conflict over the world scaling.

***********************************************************************
*    . Jeremy Lee s047@sand.sics.bu.oz.au    Student of Everything    *
*   /|            "Where the naked spotless intelect is without       *
*  /_|              center or circumference. Look to the light,       *
* /  |rchimedes      Leland, look to the light" - Dale Cooper         *
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