These two videos illustrate a powerful point: perception is often based on assumptions we draw from our perspective. The images presented (in one case a portrait, and in the other case a glass of water) can only be seen from a very specific vantage point. When I see the subjects of the videos from the intended vantage point, I want to draw conclusions about their real-world properties. For example, I assume the portrait is flat and that the cup of water is three-dimensional. My recurring “surprise” at discovering that the objects are not as they appear suggests that there could be an infinite number of three-dimensional scenarios that can produce any two-dimensional scene.
(I thought the Ok Go “Writing on the Wall” video was another really cool example of this!)
This also reminds me of the Ames Room Illusion: