I managed to find this answer here where Christian Rau says "axis/angle rotation (a,x,y,z) is equal to quaternion (cos(a/2),xsin(a/2),ysin(a/2),z*sin(a/2))"
Assuming I know what rotation I need to perform, how would I represent it? eg, finding the quaternion that rotates 30 degrees around the z axis.
Any help would be greatly appreciated.
edit** I got as far as writing out "(cos(15),0,0," and then got confused on z * sin.