For those that love optical illusions – and a good explanation for the mind-bending properties of them – finding one you haven't seen before is a real treat. And that's just happened with this (I admit, fairly old) Super Mario optical illusion that perfectly encapsulates relative motion – and gives a new perspective on the techniques used in game design.
Created by a psychologist who has a host of optical illusion and computer science-related content on his YouTube, this illusion sits at the sweet spot between his two interests. In the video, Mario appears to be jumping up and down, with the Koopa shell moving side to side. But when the background stops moving, you see that they're actually moving round in circles. Relative motion is behind many of our favourite optical illusions, and this is a great example. See it below and read on for more explanations
Sebastiaan Mathot's video shows that though the background that seems to be moving around in circles, making the shell and Mario seem like they're moving in straight lines, it's actually the other way around. It's how the two elements are moving in relation to each other that creates the illusion. This sort of shot feels common to video game design, in which the background and elements often play off against each other to change the gamer's perspective.
A similar thing happened with this real-life illusion in which a plane appeared to be completely still in the air because of the way the viewer was moving around it. But this was called "The parallax effect" because one of the elements was totally still. It still, however, shows how the movement of two objects can impact the appearance of them and create an illusion. This is often seen in web design through the best parallax scrolling websites.
