So, didn't really pay attention to the article, but wow, that spinning mask[0] in interesting! Somehow, the effect doesn't work looking at only the forehead[1]

So, didn't really pay attention to the article, but wow, that spinning mask[0] in interesting! Somehow, the effect doesn't work looking at only the forehead[1] which I would have assumed means because my brain doesn't recognize it as a "face". However, the effect does work for me still only looking at the neck[2] which I can't explain other than something with the shading? Cool stuff! [0] https://i1.wp.com/slatestarcodex.com/blog_images/spinning_mask.gif https://i1.wp.com/slatestarcodex.com/blog_images/spinning_ma... [1] https://www.dropbox.com/s/io9nsrpp52waxq5/spinning_mask_upper.gif https://www.dropbox.com/s/io9nsrpp52waxq5/spinning_mask_uppe... [2] https://www.dropbox.com/s/te0s3wgf6rilf4a/spinning_mask_lower.gif https://www.dropbox.com/s/te0s3wgf6rilf4a/spinning_mask_lowe...