title: When I have two orientation quaternions, how do I find the rotation quaternion needed to go from one to the other?
body: <p>I'm using quaternions in my game, and I'm wondering how, when I have two orientation quaternions, I can get the rotation quaternion needed to go from the first one, q1, to the second one, q2.
  I'm self taught, so there may be obvious solutions missing from my vocabulary.</p>
  
  <p>In equations, what I'm doing when I rotate from the first one to the other is as follows:
  q2 = r * q1</p>
  
  <p>However, now r is the unknown. Do the rules of algebra count here too? If that's the case, I'd end up dividing a quaternion by another, something I can't find a good explanation for on the internet.</p>
  
  <p>I'm using a program called game maker</p>