If you adjust the velocity to v-1 it would be an incremental update, which seems natural. But if you update the velocity to d-1 (as stated) I can imagine this c

If you adjust the velocity to v-1 it would be an incremental update, which seems natural. But if you update the velocity to d-1 (as stated) I can imagine this could be a jump and even could result in negative velocity for d=0.