With all the rendering effects that make the world more realistic turned on, things were quite heavy in places with many objects: even where I got around 100 FPS with them off, turning them on dropped it below 20. By sacrificing a little accuracy, I found a realistic compromise, and it now runs at roughly the same FPS as Firestorm Viewer on ultra-high settings.
Hitoshina Viewer values comfort, so whenever objects appear, they fade in gently.
If you watch the videos, I think you’ll see the distant scenery gradually coming into view 😌