What is Displacement map?

Where a normal map only fakes detail for lighting, a displacement map changes the shape itself. White pushes the surface out, black pulls it in, and grey leaves it alone.

The catch: you need vertices

Displacement can only move vertices that exist. A flat plane with four corners can't show a brick pattern, so the surface must be subdivided densely first, or the renderer must tessellate it on the fly. That's why displacement is common in offline rendering and terrain, and used more sparingly in games.

Displacement and 3D printing

Because displacement creates real geometry, it's exactly how reliefs and lithophanes are made. Our image to STL tool is essentially a displacement map applied to a dense grid: brightness becomes height. See heightmap for the same idea from another angle.

	Normal map	Displacement map
Changes geometry	No	Yes
Changes silhouette	No	Yes
Performance cost	Low	High
Survives 3D printing	No	Yes