What is the problem with differentiating a quaternion? E.g. the time derivative of the quaternion w.r.t. a fixed angular velocity is given here: https://fgiesen

What is the problem with differentiating a quaternion? E.g. the time derivative of the quaternion w.r.t. a fixed angular velocity is given here: https://fgiesen.wordpress.com/2012/08/24/quaternion-differentiation/ https://fgiesen.wordpress.com/2012/08/24/quaternion-differen... . I've more often encountered the need to integrate a quaternion, e.g. from inertial measurements or a rigid body physics model, but this is also a textbook lookup away.