[ODE] rotation matrix from normalized vector?

[Ken MacLeod]

Hi,

If you require a rotation matrix from a normalised line (axis) then use
dRFromZAxis. If you use this matrix to set the orientation of an object
then you will find that the orientation that the object assumes about
that axis is fairly random. If you require the object to maintain a
specific orientation about your normalised line then use dRFrom2Axes.
This generates a matrix from your line and an up vector.

I'm using dRFrom2Axes in my own project at the moment and I think that
it may be more useful than using dRFromZAxis.

Ken