Re: Portals vs Links

Chris Marrin ([email protected])
Fri, 5 May 1995 13:43:27 -0700


> your explanation of how to create an interactive VRML world in the same
> sense of the InPerson whiteboard is interesting, but I am concerned
> about synchronization problems between clients. Suppose one
> client/browser has a 14.4 connection, while another one is located at
the
> other end of a T3. Also, because of network traffic, it takes forever
for
> packets to even get _routed_ to the 14.4 modem, let alone transfer over
> the modem. Then, under your model, the user of client A@T3 could make
> changes to his world (say, take the coffee off of the maker) which would
be
> transfered to the server; unfortunately it takes almost 1 minute for
this
> message to reach client [email protected]. Meanwhile, the user of client B decides

While I think latency is a problem, I don't think this is a good example.
There will be cases where interaction and telepresence is impractical.
Taking a minute for message transfers will make ANY scheme unreasonable.

One interesting way to combat latency is with a simple restriction on
object interaction. If a user could interact with an object only when
s/he grabs it then the grab operation could have a ACK model, preventing 2
users from interacting with a single object. If 2 users try to grab an
object at the same time, one will win and will get the ACK, the other will
not. This is essentially how the "baton passing" in InPerson works. The
overhead would not be bad because the ACK would occur only during an
object grab.

Is this an unreasonable restriction?

-- 
chris marrin      Silicon      http://www.sgi.com/Products/WebFORCE/WebSpace
(415) 390-5367    Graphics  ," http://reality.sgi.com/employees/cmarrin/
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"As a general rule, don't solve puzzles that open portals to Hell."-...-'
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