[ODE] problems with amotor

[Jason Mallios]

I notice most questions on AMotors don't get responded to by this forum,
and others, like http://ode.petrucci.ch/, don't have much to offer.

Is it widely accepted that this class is broken?  I've tried to implement
most examples from years of community correspondence and none have worked
as expected.

Outstanding issues include:

- How do you get a non-zero vector representing the
automatically-calculated axis 1 in Euler mode?

- How can you get a relative angle between two Ball and AMotor-connected
bodies in User mode, since dJointGetAMotorAngle returns the initial
angles only in this mode?

- When or will dJointGetAMotorAngleRate be implemented and added to an
official release?

- Given a world-space torque, calculated as a single vector, how can you
reliably apply it to dJointAddAMotorTorques without euler-angle gimbal
lock?

Jason Mallios

On Sun, 8 May 2005, Smoel zonder snor wrote:

> Hi
>
> I'm working on a simulation of lego-models and I'm having the
> following problem: I create some amotors in Euler mode and I try to
> rotate them ( rotation around 1 axis only ).  When the one axis I
> rotate around crosses the origin, it works perfectly.  When the axis
> doesn't cross the origin, it rotates around the axis parallel with it,
> but which crosses the origin ( so it rotates around the direction of
> the axis ).  As I understood from
> http://ode.org/ode-latest-userguide.html the only thing I have to do
> to make an amotor rotate is enter the axes, attach the amotor to the 2
> concerning body's, and create a hinge joint between the same 2 body's.
>  This doesn't seem to work.
>
> Could this be the consequence of the following:  I place all of my
> body's in the origin, so I get a relative position and rotation during
> the simulation to work with.
> If this is the cause of the problem, I don't really know how to solve
> it, because there can me more than one amotor in a body in my
> structure, so I can't set the body position to the centre of the
> amotor
>
> Any help would be welcome.
>
>
> thx in advance
>
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