Copy of Dot Disc

Saw an image on Tumblr that had me curious... what makes the spiral effect?[br][br]Inspiration: [url]http://beautyandthemaths.tumblr.com/post/89959942948[/url][br]Gifs at: [url]http://mathhombre.tumblr.com/post/89990751944/dot-disc-inspired-by-that-second-image-from-the[/url]
More GeoGebra at [url]mathhombre.blogspot.com/p/geogebra.html[/url]

Information: Copy of Dot Disc