[fragmede]

there's probably some optimization that you can do, but you can't know that the second frame isn't the conclusion to a move from 10 frames ago that is what reveals a giant area.

    frame 0: open door
    frame 10: still can't see past edge of door
    frame 11: door opens enough to see big new area

between 10 and 11 it turns out there's a huge difference, even though they're only two frames apart.

[Retric]

The door being open or closed shouldn’t change the order of most elements. So it’s only relevant if you haven’t been sorting occluded objects.

Which gets into one of the major tradeoffs in rendering engines, do you try to minimize the average effort per frame or the worst case effort per frame.