May be as simple as switching automatically between short, medium and full vis range depending on the current FPS trying to keep always a minimum FPSs set by the player.
Of course, a better way would be to make the transition smoother or, at least, let the player to assign the desired ranges for short, medium and full visual ranges.
It would be important also to keep the "dots" independent of visual range. Currently, if you switch from full to short visual range, far dots in the sky dissapear.
