[ODE] Forward-correcting force

[Jean-Sebastien Guay]

Could anyone please help me out with this?

Thanks in advance,

J-S


> Hello,
>
> I'm having trouble refining the idea of forward-correcting force that Jon
> Watte
> gave me the first time I asked about modeling the movement of a submarine
> underwater.
>
> What I would like is that if the sub currently has a nonzero linear velocity,
> but that I turn it a bit so that its direction vector is no longer lined up
> with the linear velocity's direction, the linear velocity should come back
> gradually (quite quickly in fact) to line back up onto the sub's direction
> vector.
>
> It isn't that hard, normally I would think a quick dot product and then a
> force
> in relation to that would work. But I'm still having trouble with it. Here's
> what I have:
>
>     Vector right = m_Direction .Cross(m_Up);
>
>     // '*' between 2 vectors is dot product in (GetLinearVelocity() * right)
>     Vector fcf = m_Direction *
>         (GetLinearVelocity() * right) * -1.0f * m_Mass;
>     GetPhysicsObject()->AddForce(fcf);
>
> The problem with this is that it does bring back the orientation to the
> direction (not fast enough yet, but I can tweak that later), but it
> introduces
> too much new speed. My sub is supposed to have a given max speed (m_MaxSpeed)
> and after a few turns with this force enabled, I'm going really a lot faster
> than that.
>
> Just for reference, my acceleration function goes roughly like this:
>
>     if (GetLinearVelocity().GetLength() < GetMaxSpeed())
>     {
>         Vector force = m_Direction * m_Mass * m_Acceleration;
>         GetPhysicsObject()->AddForce(force);
>     }
>
> Perhaps there's a better way of bounding the linear velocity of an object?
>
> Can anyone point me in the right direction please?

--
______________________________________________________
Jean-Sebastien Guay     jean-sebastien.guay at polymtl.ca
                         http://whitestar02.webhop.org