# Excel Optical Illusions #17

This week's Excel Optical Illusion is called Breathing Square.

Notice the blue square, spinning in the background. To most observers it looks as if it is pulsating in size, breathing if you will. I can assure you that this is an illusion - the blue square remains a constant size at all times.

The attached workbook has a check box that toggles the masking yellow squares transparent, revealing the truth. There's also a check box governing the animation.

Most of my Excel Optical Illusions are inspired by Michael Bach's incredible site, and this one is no exception.

Regarding this illusion, the following excerpt is from Michael's site:

Usually, we are remarkably adept at detecting and identifying surface boundaries despite incomplete optical information. However, in "breathing illusions", rigidly rotating surfaces appear to pulsate or deform, even though a straightforward process of geometrical interpolation across space would reconstruct the veridical surface boundary. It is generally believed that such nonrigid outcome depends on a failure to apply a rigidity constraint across spatiotemporal discontinuities (more: Bruno 2001).

Sorry for being a day late on this illusion - minor emergency dealt with.

The workbook is an .xls and so should work in all versions.

Here it is:

Here's a list of other animated charts on Excel Hero:

- Excel, A Presentation Platform (Number Spiral)
- Lilac Chaser (Optical Illusion)
- Stereokinetic (Optical Illusion)
- Illusory Contours (Optical Illusion)
- Breathing Square (Optical Illusion)
- Enigma (Optical Illusion)

Very cool. I stared at it for a while before I read the description and I couldn't figure out what the illusion was supposed to be. I didn't notice that it was a spinning square behind the four frames. Neat effect, fo sho.

Awesome.
Can you just confirm if I got it correctly: had you to manually bulid the frames/series one by one rotating the shape etc? (or you used a sub not in the released file?)

@Nave -

I started doing it one-by-one, and then quickly decided a little sub was way better!

Regards,

Daniel Ferry
excelhero.com

I'm using Excel 2003, and for me it's not just breathing, it's spinning like an industrial fan. How do I slow the rotation?

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