This optical illusion is floating around the web - not sure where it came from. But I was curious how it worked, so recreated it in NodeBox and turned it into an animation.
To make it I converted the original JPEG into an SVG using an online converter service and used that as a template. Nothing too mysterious: four concentric circles decorated with evenly spaced black and white rectangles. I had to slightly adjust the spacing to ensure an even number of rectangles in each circle. The rectangles are rotated according to their angle offset plus or minus 18 degrees on alternating circles.
The attached network includes the logic to display the template, but the template nodes are disconnected from the combine node to create stills and movies. Original JPEG, converted SVG, NodeBox network, and movie output attached.
Enjoy!
John
