Question

Why do 3D holograms need curved lines?

Answer 1

Bar codes on items such as food and home appliances are also holograms, used to make sure nothing gets stolen. Holography is a photographic technique that records the light scattered from an object, and then presents it in a way that appears three-dimensional.

Answer 2

No CD Case, No Tape 3D Hologram Pyramid: the Quickest and Easiest Way to Make Your Own.