[ODE] Resetting positions of jointed objects

[Mark Fournier]

Is there any way to build a jointed object, and then set the position in such a way that all objects move in a coordinated fashion, maintaining their positions and joint orientations relative to each other? I would like to be able to instantiate a vehicle, and then place it where I need it, rather than build it in place.

Originally, I used geom offsets, linked the objects by the joints, and then set the position of each object to the same position and orientation. According to a graphic representation of the geoms, this worked. But the mass is attached to the bodies, and this mass moved with the bodies. So rotating the wheels caused the vehicle to twist and jump as the masses whirled around it. (I tried adjusting the mass with dMassTranslate, but that didn't seem to help.)

Furthermore, moving the pieces by setting the positions seems to update the relative positions which the joint takes to be the normal positions--and I haven't even tested yet what changing the orientations after linking would do to the joint axes. 

Any suggestions?

Thanks,
Mark Fournier
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