[ODE] Slow down sphere

[David Walters]

> The problem is, that this solution doesn't work very fine for everything else than flat grounds.
>
> Is there another solution for that?

An off-the-cuff reply would be to use the normal from the
sphere-trimesh contact point to determine the flatness of the ground -
a dot-product with 'up' will allow you to get the cosine of the
contact angle and you can use that to scale your dampening
accordingly.

Regards,
Dave