The superimposition image reveals the shapes of the base layer stretched along the vertical axis.
If the complex shape of the base layer is a sequence of symbols (e.g. a horizontal text) compressed along the vertical axis, then the superimposition of the revealing layer can restore the original proportions of these symbols.
The speedup factor is expressed by the following formula: Negative values of vm / vr signify the movement of optical shapes in reverse direction.
When pr > pb, the magnified shapes appear normally, but they move in reverse direction compared to the movement of the revealing layer.
When pr < pb, the magnified shapes appear inverted along the vertical axis, but they move in the same direction as the revealing layer.