MacKay first observed this effect on the wallboard of a BBC studio: the broadcasting staff had been annoyed by illusory shadows running up and down blank strips between columns of parallel lines.

Given the more global effect of the stop node on the entire process, we have to be careful putting a stop node in process models that can have several branches executing in parallel.

You press one button, and hundreds of parallel graphics computing cores produce the effect of vastly detailed 3D worlds.