[Double Naught Spy]

While not directly gun or doorway related, but conceptually, there is a neat graphic in the original Star Wars movie that shows the Death Star (or whatever it was called), coming around the planet and on the command consoles, you could see pie slices being add as it came around, the slices showing the additional new territory it could shoot until finally one of those pieces of pie is displayed over the intended target.

With people and doors or corners, it is more complicated than that, but the movie should give you a good working visual concept referencd.