[ODE] Updating dynamic game element's position (and shape?)

Gonçalo Lopes goncaloclopes at gmail.com
Fri May 25 06:42:39 MST 2007

Hi all,

My team is currently starting exploration on physics for augmented
reality environments, meaning that the position of some virtual agents
in the 3D world is actually updated by a tracker algorithm from a web
camera following some interesting feature in the real world.

This means that if we want to integrate these agents into a physics
world like ODE, we would have to continuously update their respective
bodies' positions every frame. This can easily be done, but
unfortunately lots of physical movement characteristics are lost
(velocity/acceleration). Essentially it is as if the object
"teleports" to each new location, with 0 velocity and null force.

This has major implications for realistic collision detection and
collision handling, since the momentum of the object is always 0. We
could work around this by dynamically calculating the position
derivative to get at the velocity, but we've grown painfully aware
that it is not such a good idea to hammer velocities away at ODE
objects, since the simulation can become quite unstable.

My question is: has any solution been considered that would allow for
stable integration of external position updaters with an ODE physics
world in a way that would preserve physically relevant historical
information (like velocity/momentum)?

Best regards,


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