[ODE] restraining rotation along axes

[Chris Campbell]

> Hi, what is the best way (if it's possible) to ensure
> that a rigid body (say falling under gravity and then
> colliding with static geo) can only rotate around the
> Y axis when it hits something?

Maybe you could use hinge and a hinge2. The hinge would be attached to the
static environment and its axis aligned with the y-axis, with no stops. Then
the hinge2 is attached to this with: axis1 perpendicular to the y-axis, no
stops, no ERP; axis2 aligned with the y-axis. In this case the body attached
to the hinge2's axis2 would be free to move anywhere in the world, but only
rotate on the y-axis. Of course you'd need an intermediate body between the
two hinges to attach them to.

ChrisC