[Algorithms] vrefresh jumpiness

[Madoc E. <tm...@ti...>]

I've noticed that whenever framerates drop below the monitor refresh rate
renderings look they're jumping back and forth, it basically looks like
there are more offset images overlayed. The problem is most noticeable with
vsync enabled. This problem is visible in all programs and hardware I've
seen and it's _really ugly_. I'm puzzled that I've never seen it mentioned.
I might even have thought that it's some optical illusion that I only am
subject to if it weren't that all my collegues agree that it's very
disturbing (something in the air at the office?).

Anyway, I can't quite understand why it looks as bad as it does. I guess
It's just to do with the way we perceive the monitor's flickering image and
there's just nothing to do about it, I can't seem to improve it. Has anyoene
ever tried to correct it with any success? Am I missing some really obvious
reason why it can't be?

Cheers,
Madoc