[vos-d] thought problem 1: physics

[Peter Amstutz]

That's very interesting.  Which simulation engine is this?

Also, to reiterate my previous email, would fixed-point math improve the 
situation any?

I suppose one thing to keep in mind is rigid body simulation for the 
purposes of games just needs to be "good enough" and look reasonable.  
Practical uses of rigid body physics in games that I have seen tend to 
have quite a lot of dampening to prevent the system from flipping out.

Physics is something I haven't solved in VOS.  The current ter'angreal 
uses client-side "physics" (really just trivial graviy and collision 
detection) but proper rigid body physics (so that users can push and 
pull things, stack things up and knock them over, etc) will likely need 
to be managed by the server.

On Fri, Feb 02, 2007 at 11:29:35AM +0900, chris wrote:
> On 2/2/07, Peter Amstutz <tetron at interreality.org> wrote:
> >Well, I assume this is a trick question.  Obviously it *should* do the
> >same thing, but because of tiny changes in floating point precision,
> >that isn't guaranteed, and the further you go the less likely it is to
> >produce the same results.  Do I get a cookie?
> 
> yup - even tho it is only 10m the difference can be surprisingly large
> and obvious just from looking at image: out of proportion to the
> difference in resolution at 10m (which is about 1.6 x 10^-15). See
> attached image.
> 
> chris
> >
> >On Fri, Feb 02, 2007 at 09:26:43AM +0900, chris wrote:
> >> This is in response to Reed's question in earlier thread.
> >>
> >> Thought problem 1: physics
> >>
> >> Suppose I am going to do a rigid body simulation. I put one box (box1)
> >> on a plane, at the origin and hold another box (box2) suspended a
> >> meter above the plane nearby. I release box2 at time t=20 and it
> >> bounces, perhaps collides with box1 then eventually comes to rest. I
> >> snap an image of the rest state of the sim.
> >>
> >> Now I repeat the entire sim after first shifting everything (boxes and
> >> plane) by 10m. The boxes and plane are in exactly the same relative
> >> position as before. I drop box2 at t=20, let it bounce and snap an
> >> image of the sim when it is at rest.
> >>
> >> Question: will the two images of the two experiments show box2 in the
> >> same rest position relative to box1?
> >>
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> >
> >--
> >[   Peter Amstutz  ][ tetron at interreality.org ][ peter.amstutz at gdit.com ]
> >[Lead Programmer][Interreality Project][Virtual Reality for the Internet]
> >[ VOS: Next Generation Internet Communication][ http://interreality.org ]
> >[ http://interreality.org/~tetron ][ pgpkey:  pgpkeys.mit.edu  18C21DF7 ]
> >
> >
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-- 
[   Peter Amstutz  ][ tetron at interreality.org ][ peter.amstutz at gdit.com ]
[Lead Programmer][Interreality Project][Virtual Reality for the Internet]
[ VOS: Next Generation Internet Communication][ http://interreality.org ]
[ http://interreality.org/~tetron ][ pgpkey:  pgpkeys.mit.edu  18C21DF7 ]

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