Originally Posted by SystemicAnomaly
^ Not sure that your additional images resolve all the issues. It clearly shows that the racket is travelling upward before and after contact. However, in this case, the ball the ball appears to be falling (at a slower rate than the toss) after contact. Did this serve go over the net? Was the server jumping and how tall is he?
Quite a few slow-motion videos, such as the one I posted above, show that the racket face appears to be slightly closed yet the ball rises for a while after contact before falling. There may very well be some cases where the ball is still falling slightly just after contact (such as a with a very tall server who is jumping). OTOH, many videos show the ball rising. A single case is not necessarily representative of most serves.
There are two more examples of the ball direction.
Figure 7. Direction of the balls around contact
Again, the balls move downward.
Videos donít show server jumps and balls near the net.
IMO, in case of Twist serve ball usually isnít rising, but Iím not sure.