[Opensim-dev] PhysX vs. BulletSim vs. ODE

Wed Feb 3 20:58:12 UTC 2016

I want to suggest you also test with 15 or so actual avatars logged in. I
would be very interested to see if everything looks smooth.

A couple years back in Second Life we made AI fish that would swim and
school around using physics. We had hundreds of them out and it looked and
worked great, with just us 3 developers logged in to the sim. When we
brought in about a dozen students on very plain avatars did things suddenly
become much different, the fish where rubber banding all over the place.

The sim statistics didn't change, and when we did some extra test we saw
the fish where actually where they where supposed to be, but we just
weren't seeing them in the correct place. We came to a similar conclusion
as Micheal,  the simulator just wasn't able to sent all the updates to all
the avatars quick enough.

This being different technology, I would love to see how it handles with
hundreds or thousands of physical objects moving around, sending object
updates to a small class worth of avatars logged in.

Regards.

On Wed, Feb 3, 2016 at 9:49 PM, Michael Emory Cerquoni <
nebadon2025 at gmail.com> wrote:

> Sure, OpenSimulator like many server applications, like MySQL or
> Apache are not configured for maximum performance out of the box, the
> default settings are chosen to allow the broadest range of hardware to
> run a quick test to see if OpenSimulator can work for you or not.
> Personally I think all Physics engines should be run on their own
> thread, having the physics engine share a thread with the heartbeat
> loop is a bad idea and will cause performance decay almost the instant
> any kind of stress is put on the chosen physics engine and if you
> notice in my video the Sim FPS never budges from 55fps while Physics
> takes a real beating, even so with BulletSim set to use its own
> thread, its still only a single thread, if we can resolve the major
> issues with sending so many updates to a viewer either by new
> protocols or fixing the OpenSimulator HTTP server, or a completely new
> viewer technology, improving physics beyond this to say
> multi-threading or GPU accelerated physics seems like it won't be as
> beneficial as we all hope it would.
>
> On Wed, Feb 3, 2016 at 3:28 PM, Sean M <mondesire.sean at gmail.com> wrote:
> > Thank you Michael for your comments.
> >
> > The preliminary data that I shared earlier was generated from default
> > settings across the different engines. The MOSES Team's ongoing and
> upcoming
> > tests will analyze the impact of different configurations between the
> three
> > engines.
> >
> > Because OpenSim can be executed on a wide range of platforms to satisfy
> > diverse use-cases, thorough and exhaustive testing can be difficult for
> just
> > the small MOSES Team. Therefore, I hope you and other members of the
> > community can take the time to deeply analyze our contribution and
> provide
> > quality feedback upon final release. With your help, others can make the
> > educated determination if adopting and enabling PhysX is right for their
> > sims.
> >
> > All the best,
> > Sean Mondesire
> > MOSES Team
> >
> > On Wed, Feb 3, 2016 at 1:57 PM, Michael Emory Cerquoni
> > <nebadon2025 at gmail.com> wrote:
> >>
> >> Here is a quick video I made just now with 10k physical spheres, its a
> bit
> >> slow its hard to render that much and record at the same time, but you
> can
> >> see BulletSim does quite well considering what is going on and its far
> >> beyond what is shown in the chart for BulletSim.
> >>
> >> https://www.youtube.com/watch?v=0RBpDDEAg_o&feature=youtu.be
> >>
> >> On Wed, Feb 3, 2016 at 12:20 PM, Michael Emory Cerquoni
> >> <nebadon2025 at gmail.com> wrote:
> >>>
> >>> I totally agree, my entire point was that there are much lower
> >>> performance issues than the physics engine, doesn't matter if the
> physics
> >>> engine can handle 100,000 objects or not opensimulator can not
> adequately
> >>> update the viewer, very much probably because of the HTTP server,
> totally
> >>> agree, if my wording was misleading I apologize.  I however do not
> agree
> >>> with the assessment being made about bulletsim, I have seen much higher
> >>> numbers than what is being shown here, I would like to see another run
> added
> >>> to these results with BulletSim configured to run in its own thread
> and not
> >>> the main simulator heartbeat loop, you would see much different
> results I
> >>> suspect, If anyone needs to see a actual demonstration of a simulator
> with
> >>> 10's of 1000's of physical objects in BulletSim i can certainly
> demonstrate
> >>> it.
> >>>
> >>> On Wed, Feb 3, 2016 at 12:12 PM, Cinder Roxley <
> cinder at alchemyviewer.org>
> >>> wrote:
> >>>>
> >>>> On February 3, 2016 at 10:02:57 AM, Michael Emory Cerquoni
> >>>> (nebadon2025 at gmail.com) wrote:
> >>>>
> >>>> semantics, whatever the limitation is OpenSimulator can't update the
> >>>> viewer with more than about 1000 objects, I do all of my tests
> locally on
> >>>> 1000Mbit network, so if thats not enough what is? maybe I need 10TB
> network?
> >>>>
> >>>> Not semantics, accuracy matters when you’re placing blame on the wrong
> >>>> components. The fact that you even see objects rubberbanding is
> enough to
> >>>> know the viewer is capable of rendering those scenes. It’s trying to
> predict
> >>>> where that object is going when it hasn’t received that object’s next
> >>>> update. I can rez 3,500 objects in Second Life before seeing this
> behavior.
> >>>> It’s far lower in OpenSim because the HTTP/UDP server is crap.
> Convenient,
> >>>> but none-the-less crap under load.
> >>>>
> >>>> Naturally, you aren’t going to see people rezzing 3,500 balls and
> >>>> dropping them in a real world scenario, but you may have 10,000
> physical but
> >>>> not actively thrown around objects in a scene, and bullet sim is less
> than
> >>>> happy when this happens.
> >>>>
> >>>> --
> >>>> Cinder Roxley
> >>>> Sent with Airmail
> >>>>
> >>>> _______________________________________________
> >>>> Opensim-dev mailing list
> >>>> Opensim-dev at opensimulator.org
> >>>> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-dev
> >>>>
> >>>
> >>>
> >>>
> >>> --
> >>> Michael Emory Cerquoni
> >>
> >>
> >>
> >>
> >> --
> >> Michael Emory Cerquoni
> >>
> >> _______________________________________________
> >> Opensim-dev mailing list
> >> Opensim-dev at opensimulator.org
> >> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-dev
> >>
> >
> >
> > _______________________________________________
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> >
>
>
>
> --
> Michael Emory Cerquoni
> _______________________________________________
> Opensim-dev mailing list
> Opensim-dev at opensimulator.org
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>

-- 
Jeroen Frans
Virtual World Technology Specialist @ http://VesuviusGroup.com
Second Life: Frans Charming
blog about SL @ http://secondslog.blogspot.com

"The best way to predict the future is to invent it." Alan Kay
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