As you walk past a portrait that looks straight out, the eyes appear to follow you around the room. Similarly, roads that go from the front of the picture plane (that is , the bottom of the image) back towards the horizon appear to change course as one walks around them; pointing fingers (i.e. ... All are geometrically valid solutions, yet a viewer will interpret the image only in accordance with the plan labeled 97.
|Title||:||Human Vision, Visual Processing, and Digital Display|
|Publisher||:||Society of Photo Optical - 1995|