21 September 2008

How easily we are fooled: The rotating grid illusion

Filmmaker and animator David O’Reilly (who came up with the concept for iHologram) has noticed an interesting property in this animated GIF:

He writes:

While working in 3D last year, I discovered this optical illusion: A large grid seen rotating at a certain speed will appear to group itself into smaller grids, spinning independently.

See O’Reilly’s website for more examples (and his theory on why this happens).

For more optical illusions, watch Al Seckel’s TEDTalk on how easily we are fooled; or Dan Dennett’s talk on our gullible minds. As Dennett says, we need to understand how easily we are fooled, in order to understand the nature of consciousness itself.

Discuss this Blog Post

Tom Tubbs
Sep 22 2008
What happens if the image is circular? Is the effect due to the constraint of the image’s boundaries?
mike powers
Sep 22 2008
I absolutely love his film work…
Mike Sitoris
Sep 22 2008
This is temporal aliasing, not an optical illusion.
http://en.wikipedia.org/wiki/Temporal_aliasing
Cristi Stoica
Sep 26 2008
There is an explanation of O’Reilly’s illusion at http://unitaryflow.blogspot.com/2008/09/illusion-of-center.html

It is graphical: http://i361.photobucket.com/albums/oo56/holotronix/RotatingGridCross.gif

The page also contain a rotating grid with two real centers: http://i361.photobucket.com/albums/oo56/holotronix/RotatingGridFixedPoints65.gif

created using Pythagorean triples.
Mark Garland
Sep 25 2008
Imagine this as a desktop background… crazy!
Cathy Ley
Sep 25 2008
yeah, you will see the entire grid when you move your head in circle in the same speed/direction with it.

now… check this one out:
young woman or einstein?
Barbara Hauser
Sep 26 2008
Is it just me, or does it spin more slowly when you squint at it?
ben basner
Feb 24 2010
actually it is fake… its not 5+ separate spinning grids (supposed illusion) nor is it 1 big grid (what it claims).
frame 43 frozen (below) clearly shows a 2nd static grid offset slightly that fades in from black and back out again. this 2nd grid fading in and out is what gives the illusion… not spinning 1 big grid. the 2nd grid is not seen while in motion as it is dismissed as motion blur. for those that do not believe me, download the gif and open it up in something that can view it frame by frame (slow motion will not be slow enough to see the detail). as the main grid goes around you will see a 2nd non-moving grid flash in and out (this is not a trail as frame by frame eliminates trailing effects… it also doesn’t move).
http://img8.imageshack.us/img8/4407/image0kf.jpg