[ODE] Simulator explodes on zero Quaternion normalisation

[Joe Ante]

> you can consider a quaternion to be a 3d vector of length 1, representing an
> axis in space (starting from (0,0,0) obviously), plus an angle (rotation)
> arround that axis. So in effect a quaternion is a custom rotation (instead
> of giving Euler angles or rotations arround X,Y,Z axis [in which case the
> order of rotation X,Y,Z, or Z,Y,X or Y,Z,X etc. is important])
You are confusing axis-angle rotation representations with quaternions.

A quaternion is a 4d complex number. If the quaternion is of unit length it
represents a rotation.
Calling dNormalize4 should be used to normalize a quaternion.

Joe Ante