[ODE] Naive Pitch/Roll/Yaw rotation questions

[Doron Tal]

 From what I understand, you want to transform the roll axis into world
coordinates.  Here's how you do it:

1) get the rotation matrix corresponding to the body's current
world-coordinate-frame rotation, e.g. using dBodyGetRotation().

2) done!

The first column of the rotation matrix is the body-coordinate-frame
x-axis (or 'first' axis), expressed in world-coordinates.

The second column of the rotation matrix is the body-coordinate frame
y-axis, expressed in world-coordinates.

The third column of the rotation matrix is the body-coordinate frame
z-axis, expressed in world-coordinates.

Typically one chooses x- y- or z-axis for the roll axis, so here you
go, there's your x- y- or z-axis (i.e. roll axis) in world frame.

[ The columns of R (body's rotation matrix, in world-coordinate-frame)
represent the world-frame coordinates of unit vectors along the
principal axes of the body-coordinate-frame. ]

Best Regards,

-Doron


--
Doron Tal,  USRA/RIACS Research Scientist
NASA Ames Research Center, Mailstop 269-3
Moffett Field, CA 94035-1000, USA
email: dtal at email.arc.nasa.gov