"In mathematics, physics, and art, a moiré pattern (/mwɑːrˈeɪ/; French: [mwaˈʁe]) is a secondary and visually evident superimposed pattern created, for example, when two identical (usually transparent) patterns on a flat or curved surface (such as closely spaced straight lines drawn radiating from a point or taking the form of a grid) are overlaid while displaced or rotated a small amount from one another." https://en.wikipedia.org/wiki/Moir%C3%A9_pattern