This duck is spinning left to right, or is it right to left. You can control it with your brain... it's tricky though.

What: This silhouette illusion is probably one of the harder to replicate, that being said, the effect and awe of getting it working is also probably one of the most amazing to me. Here you see a duck that is spinning, the thing is, with a silhouetted image there isn’t really enough visual data to tell if it’s going clockwise or anticlockwise as there are multiple positions where the image looks exactly the same. The most popular version of this is the spinning dancer [1] by Nobuyuki Kayahara.

In my version I’ve used a simple duck, I had experimented with a few different models, but funnily enough the code to render this in 3d [2] was using a rubber duck, and it felt like it was perfectly appropriate to use it, and in many ways the simplicity of the duck made it a lot easier for me to be able to switch the direction with my mind.

How To: You can use the configurations to change the ducks' direction, but you shouldn’t need to… that said, if you can’t get it to rotate with your brain you can click the button and the direction shift will make your brain see it’s spinning the other way, you can then watch it for five to ten seconds, close your eyes briefly and switch it back, open and you shouldn’t see the change. I have been able to flip it semi-regularly by doing a large blink when the duck is facing toward me (or away).

Another fun trick is to put a mirror up next to this (or your phone next to a mirror), you would expect to see two ducks rotating in different directions, but that is not always the case!

Cites and Extras:

I've researched these optical illusions in my spare time but am clearly not any kind of expert and my explainations are pretty smooth brained, if you find something mis-cited, earlier examples, or general mistakes please new let me know via, be kind!