Chevron Field
Bands of zigzag, every one the same and every other one a shade apart. The eye reads the pairs as ridges and folds the sheet.
About this pattern
Chevron bonds · weaving and parquetry
A chevron is two straight lines meeting, which is nothing; a field of them turns into a corrugated surface as soon as alternate bands take different tones. That is the whole of the effect: a repeated change of tone across a repeated change of direction is read as light falling on something folded, because in the world those two things almost always arrive together.