Fuzzy blobs. You can create odd contrast and movement illusions with sinusoidal gratings. Try different vertical and horzontal sizes with each of the patterns. Can you create moving dots as in the scintillating grid illusion? Can you create shimmering movement as in the Leviant illusion? How do size and vertical/horizontal ratio affect these? How are they affected by color, contrast, and rotation?
Download the image or copy this link to recreate it.
Sizes in terms of visual angle: ° horizontal period; ° vertical period.