Coffered Vault
A ceiling of sunk panels. Every recess is cut the same way, and the four sides of each take their own tone.
About this pattern
Coffered ceilings · Roman vaults and Renaissance soffits
A coffer is a square hole with sloping sides, and it needs no shading model to read as one: the two sides that turn toward the light take a lighter tone, the two that turn away take a darker one, and the eye supplies the depth. Pull the recess off centre and the whole ceiling turns to face that point, because a consistent direction of sinking across a field is read as a single viewpoint rather than as many separate holes.