[ODE] ODE and geom scales

[Megan Fox]

You only apply the up-force when your downwards-pointing ray is in
contact with the ground (or some other solid object).  The up-force
you apply can be calculated just by looking at the velocity of the
hovering body... if there is any component in the direction of the
downwards ray, you'll need to apply sufficient force to counter it,
and then you'll need to make sure the end velocity is such that it can
fix your hover back to the desired height.

The black magic comes in when deciding how quickly the restoring force
should act... too hard/too fast, and your object bounces around like a
pogo stick (unless you also apply a downards force, but then you've
got an oscilating movement, never mind a sticky situation for when you
actually DO want your player to move upwards in the form of a jump). 
Of course, the slower it is, the more often your player's feet will be
penetrating into the ground (though you'd never notice if you threw in
a bit of IK on the legs).

-Megan Fox

> I like the idea of the hovering CCylinder, but how does that work with
> gravity ?
> 
> If you apply a vertical force up to make the CCylinder hover, gravity
> will be disabled. Doesn't
> that lead to strange behaviors ?
> 
> F. Brebion