I'm new here so sorry if this is a really silly question but I can't solve it myself.
If I have two points on a unit sphere, A and B, and the shortest path from A to B over the surface of the sphere, then how do I calculate the direction of this line at point B (as a vector)?
Do I need to compute this using quaternions? I have read a bit about it but find it very hard to understand how to use them. Alternatively, if rotation matrices can be used I would be very happy too.