Thanks, good tip! I think the viewPosition.z is used for view-space SSAO later. I’m not sure if there’s another way it can be reconstructed, but for now I’ll take the savings of precomputing world * view.
EDIT: although I forgot, since I’m putting normals into world-space now, I do still need to pass world, but it’s better to do the multiplication once on CPU than per vertex on GPU.