[QUOTE 3924815, member: 45"]Imagine it as door- no door-door-no door. The door and no door segments are the same length. Each frame moves the train (it doesn't matter which way) the distance of the length of one segment, so where there was a door there's now no door, and vice versa. The next frame returns them. So your brain can join the frames to make it look like the train is going in either direction.
Or summat like that. It's hurting my eyes now.[/QUOTE]
Yeah that sounds familiar. I'm sure there's a proper word for it, I'll find out tomorrow. Maybe.