[ODE] what a drag

[Ruud van Gaal]

...
> > Aerodynamic drag *can't* be implemented internally.  ODE uses point 
> > masses to represent it's bodies, and geoms are created in 
> the separate 
> > collision detection engine.
...
> The one function would iterate the list of ODE bodies, get 
> their velocities and geoms, compute the cross-section area of 
> the geom as viewed from the velocity direction, and apply a 
> force proportional to the cross section area and the velocity 
> vector.  Easy, right?  :-)

But geoms are approximations to the real bodies they represent.
Any area drag component calculated this way would be grossly wrong
trying to estimate the drag of the object itself.

For cars, I just use wing objects which have their user-specified
drag/lift coefficients, and add forces to the wing center point in
longitudinal and lateral directions. Approximating a wing with say an
ellipsoid would just be totally wrong...

Ruud