[ODE] Has anybody had any luck with dJointSetAMotorAngle?

[Patrick McColgan]

I finally (hopefully) have AMotors working the way I want so here's my 
take on it:

setAMotorAngle is exclusively for User mode meaning that you are 
completely responsible for updating the motor, as far as I can see you 
aren't telling the amotor what the angle should be; you're informing it 
of what it is.

I use an AMotor to stand a cylinder upright, normally the cylinder lies 
along the z axis so what I do is first rotate the cylinder 90 degrees 
about its local x axis and position it's bottom end on a surface.  Then 
I set up the AMotor, I use 3 axis set as a unit vector along the global 
x, y and z axis.  Then I call setAMotorAngle to initialise all the axis 
to zero degrees, so in spite of ODE knowing that I have rotated the body 
I have told the amotor that this upright cylinder is unrotated initially 
with respect to the amotor.  Then each frame I calculate the angular 
difference between the cylinder's local x, y and z axes and the global 
x, y and z axes (as I use the internal rotational matrix of the body I 
have to account for my initial rotation).  The differences I find 
between each I set as new AMotor angles for the corresponding AMotor 
axes.  And that's all I have to do, the motor maintains the cylinder 
vertically.

I hope that makes sense, as I say I finally have AMotors working the way 
I want them.  But it wasn't easy.

Gerritt Brownlee wrote:

>
> I am trying to set the initial conditions of my motor.  It doesn't 
> move the joint to any angle.
>
> If I can't get the setAMotorAngle to work I guess I will have to use 
> quaternions to set the inital conditions.
>
> Please respond if you got this function to work.
>
> Thanks
>
> Gerald Boone
>
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