How to create a pixelated smoke effect style from a standard one in Side Effects Houdini, also introducing Quaternion rotations, tutorial by Tyler Bay CG Forge.
Also – please keep in mind that this is not a comprehensive definition of quaternion rotation.
This is, however, a much more accessible place to start.
Quaternions Quick Tip
Quaternions and 3d rotation
One of the main practical uses of quaternions is in how they describe 3d-rotation. These first two modules will help you build an intuition for which quaternions correspond to which 3d rotations, although how exactly this works will, for the moment, remain a black box. Analogous to opening a car hood for the first time, all of the parts will be exposed to you, especially as you poke at it more, but understanding how it all fits together will come in due time. Here we are just looking at the “what”, before the “how” and the “why”.