'Difference' between two quaternions

Question

I\'m working in Ogre, but it\'s a general quaternion problem.

I have an object, to which I apply a rotation quaternion Q1 initially. Later, I want to make it as if I

Answer 1

Think of it this way

QInitial * QTransition = QFinal

solve for QTransition by multiplying both sides by QInitial^{-1} (^{-1} being the quaternion conjugate)

QTransition = QFinal * QInitial^{-1}

It's just that easy.

• note to @Dan Park - if you disagree with my math, please post a response to my answer, don't change the math. As far as I know, it's right.