[ODE] Read out the contact forces?

[Ke]

Thanks.
For the velocity of the contact point, we used
dBodyGetRelPointVel(Wheel_body_ID,0,0,-RADIUS,wheel_vel).
here RADIUS is the radius of wheel.
>From car kinematics, all the contact point velocity
should be zeroes or very close to zeroes if the wheel
is pure rolling on the ground. But the read-out from
dBodyGetRelPointVel gave us non-zero numbers.
And we set the contact[i].surface.slip1/2 to a very
small number (1E-12), which should gives us almost
non-slip. but the read-out non-zero numbers says we
still got slip velocity. what happened?
Thanks again.

Ke

--- "Jon Watte (ODE)" <hplus-ode at mindcontrol.org>
wrote:

> This is a FAQ, and it is answered in the manual. The
> forces are zero, 
> unless you are inside the execution of your step
> function.
> 
> However, if you can get the velocity of the point of
> the body that 
> touches the other geometry, and you know your mu,
> you can calculate some 
> useful bounds on the friction force.
> 
> Cheers,
> 
>           / h+
> 
> 
> 
> Ke wrote:
> > Hi,
> > When we simulate a 3-wheel car on ground,we need
> to
> > read out the contact/friction forces between
> wheels
> > and the ground. But when I used
> > dBodyGetForce(Wheel_body_ID), what I got is
> (0,0,0)
> > all the time. Am I wrong? or any other way to do
> that?
> >
> > Thanks.
> >
> >
> > Ke
> >
> >
> >        
> >
>
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> 



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