[Opensim-dev] Using ODE for vehicles and ragdolls

[nlin (message)]

ODE doesn't have any explicit vehicle abstraction. So LSL things like
airplanes or boats would still need to be modeled with some additional
forces. What ODE does offer is joint support, including powered motors,
hinges, sliders, etc. I know it's possible to create fairly realistic car
simulations using ODE's joints.

I think the 2 approaches, LSL-based vehicles and ODE joint-based vehicles,
are complementary. LSL-based vehicles offer a simpler abstraction that can
cover different vehicle types (land, air, water), while ODE joint-based
vehicles are more oriented toward land-based vehicles and allow/require
modeling and control of each wheel and axle. It seems to me that both would
have their uses in OpenSim.

Regards,
N Lin (nlin)

2008/11/19 Frisby, Adam <adam at deepthink.com.au>

> Doesnt ODE have vehicle support internally? The concern I'd have about a
> vehicle layer over the top might be that performance is suboptimal since we
> need to run a second physics step which could introduce issues.
>
> Regards,
>
> Adam
>
> > -----Original Message-----
> > From: opensim-dev-bounces at lists.berlios.de [mailto:opensim-dev-
> > bounces at lists.berlios.de] On Behalf Of Gerhard Dünnebeil
> > Sent: Tuesday, 18 November 2008 10:40 PM
> > To: opensim-dev at lists.berlios.de
> > Subject: Re: [Opensim-dev] Using ODE for vehicles and ragdolls
> >
> > Hi
> >
> > having looked into the ODE engine I don't think it's usable for the
> > vehicle API.
> >
> > Instead i think we should put the vehicle engine on top of it.
> >
> > This is pretty easily done by adding another layer (could/should be in
> > a
> > plugin).
> > It can be called in each "Simulate" step and calculate the forces
> > needed
> > to achieve the vehicles behaviour.
> > These forces are then applied -- using the phys engine's API -- to the
> > objects.
> >
> > This way we are
> > a) ... independant (at least theoretically) from the characteristics of
> > the underlying Phys engine
> > b) ... able to implement different engines for different purposes
> >
> > I know someone (is it you, nlin?) already implemented a sailing boat in
> > OpenSim. A modular approach here would allow us to implement
> > alternative
> > friction models beyond what LSL gives us.
> >
> >
> > Just my two cents
> >
> > Gerhard
> >
> >
> > nlin (message) wrote:
> > > Hello,
> > >
> > > There's been some discussion about SL-compatible vehicles in OpenSim
> > > recently, with its higher-level abstraction of how vehicles work.
> > This
> > > would have the long-term goals of compatibility and ability to swap
> > > out physics engines while still using the same vehicle layer.
> > >
> > > SL-compatibility and abstracting vehicles from the physics engine are
> > > good goals for the long term; sort of a top-down approach (start with
> > > the vehicle abstraction, map it to many different physics engines).
> > >
> > > Complementary to this, I'd like to explore and start discussion of an
> > > alternative way of handling vehicles by using a bottom-up approach.
> > > Starting with the specific physics engine of ODE, can we use
> > > ODE-specific features to make simple vehicles?
> > >
> > > I did some experiments with OpenSim and ODE and the answer seems to
> > be
> > > yes, we can make simple vehicles with ODE by using joints. We can
> > also
> > > make ragdolls. I posted some videos to YouTube of the preliminary
> > results:
> > >
> > > http://www.youtube.com/watch?v=iYIh-eIwmjs
> > > http://www.youtube.com/watch?v=z9bedzIuxdM
> > >
> > > This is only prototype work for now, put together sort of quickly as
> > a
> > > proof-of-concept with just enough "plumbing" (data flow) to work.
> > > There are a number of issues that need to be solved for this to work
> > > cleanly. As far as I know (please correct me if I'm wrong) there
> > > hasn't been much work done to try to get ODE joints/vehicles/ragdolls
> > > working in OpenSim, but I think it's an avenue worth exploring.
> > >
> > > Is there interest in pursuing this approach for OpenSim vehicles? I
> > > would look forward to discussing some of the issues that would need
> > to
> > > be solved.
> > >
> > > Thanks,
> > > N Lin (nlin)
> > >
> > > ---------------------------------------------------------------------
> > ---
> > >
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> > >
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