Illusion Face

A simple yet effective illusion where the face seems to orientate to the viewer.

View the video to get a good look:
https://www.youtube.com/watch?v=3_YqGBlCFZM
Or check out the illusion virtually on Sketchfab: https://sketchfab.com/models/3ada924493804c8f9817bafe44685533

Most people with always see a positive face in a negative face but
the effect works best with a light source shining on it from the bottom which tricks it as if the light is shining from the top on a positive face. Additionally the standing version also works with a light shining through it from the back. (Like a lithophane effect.)

Remixed from my Melt Face: http://www.thingiverse.com/thing:651829
I squashed, cropped, smoothed and of course inverted it to get a really good illusion effect.