Quaternions

Have form [s,v] where v = (xv, yv, zv)

q1q2 = [s1,v1] [s2,v2]
= [(s1*s2 - v1*v2, (s1v2 + s2v1 + v1 x v2)]

For a vector v, we rotate to position v' by
v' = q^-1 v q v is treated as [0,v]
q^-1 = (1/||q||²)[s,-v], ||q||² = s² + v*v