[Opensim-dev] Using ODE for vehicles and ragdolls

[Gerhard Dünnebeil]

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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