Hidden Bird
What to do & see
On the above you will see a ‘bird’ flying above a background consisting of random
lines. Now press the button “Bird stop”: the bird
doesn't just stop flying, but slowly fades away until it vanishes completely!
Try it at various places – the background is so well matched to the lines comprising
the bird that we have nearly perfect camouflage.
When you have stopped the bird’s flight, and it has merged into the background,
you can try the button “Noise off”. This will reveal
that the bird is still there – just invisible.
Comment
The camouflage is broken by correlated motion. This is very similar to the
running Dalmatian (“help me 2” there). The
bird is made up of 21 ordered penstrokes and the background is the same 21 penstrokes
ordered randomly.
Reference
This is my re-implementation of the beautiful Hidden Bird demo on the ‘hidden’ former IllusionWorks
pages by Al Seckel.
That in turn was programmed by Akos Feher, who attributes the orginal drawing
to David Regan.
2012-04: Source revealed! David Regan kindly responded to my enquiry, here goes:
Regan D (1986) Form from motion parallax and form from luminance: Vernier discrimination.
Spatial Vision 1:305–318
Regan D (2000) Human Perception of Objects: Early Visual Processing of Spatial Form
Defined by Luminance, Color, Texture, Motion, and Binocular Disparity. Sunderland,
MA: Sinauer, 577 pp. [Here the bird is on the transparent bookmark and the background
in the text.]
Created: 2006-07-26
Last update: 2013-10-04