A more complicated, related example is how WW2 fighter aircraft machine guns were aimed.

There might be, for example, four guns on each wing. The aiming reticle is in the cockpit, between them. The whole shebang is adjusted so that the bullets from each side converge (for example) one hundred meters ahead of the plane, and the aiming reticle points at that spot. This adjustment has to account for the angles from left and right, as well as the bullet drop, and air drag at a particular airspeed.

Like with the rifle scope, the pilot's aiming reticle has extra marks on it to allow aiming at other distances, and especially for leading a moving target.