[Opensim-dev] Can OpenSim be used for physically realistic training simulator?

Thu Sep 4 13:58:15 UTC 2008

Hello Yassir,

I'm happy to hear of your interest in using the opensim platform for
realistic physical process simulation. There are several scattered efforts
that have looked at this, including a few I'm involved with. I'll offer
some thoughts on this, which are just my suggestions to guide your
approach. There is a larger discussion that should eventually take place on
opensim-dev when opensim is further along.

The physics engines in opensim really are not designed to be general
purpose simulation engines for models of physically realistic processes.
Domain models will have a level of detail specific to the model which
strongly determines force calculation and integration. The physics engine
in opensim is purposed for keeping avatars from bumping into things,
(hopefully soon) vehicles, and basically running the coarse level of
everyday realism that keeps the user's mind in connection with what is
happening in world. We really wouldn't want to push more realism on to the
internal physics engine until a number of other issues get resolved.

Having said that, I'm very optimistic about opensim as a platform for
scientific work. The critical point is where you factor the workload, and
specifically what you use opensim for. I see opensim more of an interface
to backend systems that perform special simulations rather than a tool to
simulate. Simulations of physical process can produce enormous amounts of
data ( I deal with close to a petabyte of all-atom dynamics trajectories).
Most of simulation data is not interpretively useful, and analysis of that
data has to be understood well enough to write papers with figures in them,
and make simple clear points about what you learned. Opensim's greatest
role here, in my opinion, sits in between the simulation and the paper
writing, closer to the paper than the simulation. The part where you're
working collaboratively to analyze what it means, and what you found. In my
experience, this comes down to simple models that make simple points, which
could not have been arrived at without the heavy realistic simulation.

Ok, so why do I think this post belongs in opensim-dev? Because the use
case of interfacing with backend simulations is a recurring one, and a
sensible way to approach that class is to bring it to a discussion of what
interfaces are needed to set up the simulations in world, execute and
manage job queues controlling the simulation, maintaining simulation
parameters, managing output and archiving, accessing meta data about the
simulation, control the data reduction from inworld, maintaining domain
specific metrics and measurement procedures, and then the interesting part:
data visualization, understanding, sharing and group discussions in the
context of the data. There are lots of aspects to that process where
opensim can bring real advances to the table, and genuinely lead to the
dismissal of contempory techniques for the great new way, but I feel
actually doing the simulation in opensim misses the point. Where we need to
focus in this context, is what are the use cases that drive easier
integration from inworld to backend systems, both for controlling backend
systems, and understanding the simple summaries of what backend systems can
tell us.

I'll invite you to think more about how best to factor your overall use
case in a way that keeps opensim as a 'thin' layer of control and shared
coarse visualization, and discuss more specifically what the actual
requirements might look like to produce results in your domain, and share
them with others.

-Mike Pitman/ Rez Tone

             Yasir Assam                                                   
             <yassam at gmail.com                                             
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                                       [Opensim-dev] Can OpenSim be used   
                                       for physically realistic training   
             09/04/2008 04:59          simulator?                          
             AM                                                            

             Please respond to                                             
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Hello,

I'm considering writing modules for OpenSim to enable me to create a
physically realistic training simulator.

In brief, my simulator has to

    * simulate & render certain physical processes realistically (e.g.
      weather events such as hurricanes and their effects on the
      environment)
    * constrain avatar movements (e.g. no flying, and impede motion on
      fatigue)
    * allow a privileged user to fast-forward/rewind simulation (e.g.
      jump forward 6 hours in the simulation of the hurricane)
    * allow a privileged user to have multiple views of simulation (I
      realise this depends in part on the client app)
    * be able to morph/add/remove physical objects in real-time for all
      users to see and interact with
    * log user actions for assessment purposes
    * voice chat with simulated distance & direction (someone far away
      in the sim sounds distant)

There's no need for the simulator to integrate with other grids (but
there's no harm if it gets that capability out of the box).

Is it sensible to build something like this on top of OpenSim or should
I just write my own engine?

Thanks,
Yasir

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