[egypturnash]

No aliasing is required. I was first introduced to moire patterns by a book with a bunch of line patterns, and a sheet of transparent plastic with other line patterns printed on it. Put the latter over the former, move it around, watch the weird effects.

[barrkel]

Moire patterns are related to aliasing: the gap between the lines on the overlay is your sample frequency, the lines on the underlying page is your signal frequency, with the angle of the two sheets modifying the relative frequency and the offset of the sheets changing the phase.