[Opensim-users] objects undergoing continuous change

[Paul Fishwick]

Crista:

Diva Canto wrote:
> I have written a region module that does traffic simulation. Here's a 
> video produced by my students:
> http://uk.youtube.com/watch?v=kJNDcurLP1w
This very impressive and nice use of OpenSim along the lines of what I
was thinking about. For teaching discrete event simulation, the entire 
messaging
passing approach seems to lend itself well to this (assuming FIFO
ordering on event queues for a region). For continuous simulation,
your vehicles appear to be updating position at a decent frequency.
Did you use llSetPos() and was there a delay or did you run flat-out
at whatever the server could muster?

For some reason, my simple test was not good, perhaps because I was
moving too short a distance during updates. I'll retry again later tonight.
>
> That was back in late August; the opensim API has changed considerably 
> since then and I haven't had time to update my module yet. I didn't 
> use physics; it was all done with periodic updates to the objects' 
> state, just like in traditional simulation. It works pretty well, only 
> starting to break when there are more than 2 avatars in scene; the 
> breakage is because we have the server behind a home DSL, so packets 
> start getting lost.
Yes, I could see how too many updates could be a problem depending on 
the server
and location of clients.
>
> In general, for doing tradional simulations forget about using inworld 
> scripting. Even if the scripting engine was already working well, 
> which is not, that introduces a lot of unnecessary overhead. 
I suppose I was wondering whether the overhead could be removed or 
minimized for
running standalone servers (or at least, servers with no more than 1 or 
2 avatars)...
> Moreover, it also imposes a programming model that is an obstacle to 
> simulations (for example, not being able to hold references to objects 
> and having to interact with them via llSay functions). 
Yes, having the option for direct referencing would be useful.
> The opensim API, on the other hand, is a joy to work with (how many 
> times have I said this? :-)

When you say the opensim API are you referring to LSL, the C# interface, 
or something else?
I've been using LSL, but haven't seen any docs on the C# API yet.

-p

>
> Diva / Crista
>
> Paul Fishwick wrote:
>> Justin Clark-Casey wrote:
>>   
>>> Yes, things are stored in memory with a regular flush to database that occurs every 15 seconds.  However, I suspect that 
>>> objects with the physics attribute are not currently persisted (from a recent thread on opensim-dev).
>>>
>>>   
>>>     
>>
>> I am curious as to whether it could become possible (in a standalone 
>> server or
>> in a grid with only one person) to do continuous visual updates for moving
>> objects (physical or otherwise). I have tried a few experiments, such as a
>> continuously moving block using LSL (setpos) and after a few seconds, the
>> behavior becomes erratic (for example, the box shoots off somewhere or
>> disappears entirely from the region).
>>
>> I realize that having fast moving visual objects does not lend itself 
>> well to sharing
>> state, but there are some instances where one wishes to simply launch a 
>> region
>> or grid and do more traditional simulation (as one might do in OpenGL) 
>> whether
>> or not the object states are shared, or on the frequency of sharing. It 
>> would be nice
>> to have this "standalone continuous object motion" as a switch-based or
>> deltatime-specified capability.
>>
>> Thoughts?
>>
>> -p
>>
>>   
>>>>  * Would it (or is it) useful to have some scripts run on the client 
>>>> rather than the
>>>>     server for less server loading? For example, could ODE run on the 
>>>> client
>>>>     
>>>>       
>>> I think that some minor stuff is done client side already (such as flexiprims).  However, I suspect one runs into 
>>> difficulties when objects can affect each other, since you would have to start communicating all this information back 
>>> to the server and somehow synchronizing it with changes from other clients.
>>>
>>> However, I am not an expert in this area.
>>>
>>>   
>>>     
>>
>>
>>   
>
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Dr. Paul A. Fishwick           E-Mail: fishwick at cise.ufl.edu
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