The short answer is that yes it is possible to rotate your tip and change the contour of the dorsum of your nose without shortening. And there are many plastic surgeons and facial plastic surgeons that can accomplish that goal. One thing that you must keep in mind, however, is that the computer generated imagery is not a guarantee of exactly what you will look like.
No plastic surgeon that I know will give you a guarantee that you will look exactly a certain way and so sometimes the imaging can be a bit unrealistic.If you present to a plastic surgeons office and say that you would like a smoother dorsum, some tip rotation, or more tip projection then your surgeon should be able to accomplish this. On the other hand, if you present to the office and say that you want to look exactly a certain way, then that may be unrealistic and you may be disappointed.
If you can explain to your surgeon what your goals are then your surgeon can tell what is possible, how it will be achieved, and what you can realistically expect as a result. Best of luck to you!