What is "photoclinometry"

n. The estimation of slope information by the analysis of brightness distribution in a photograph of a geologic surface (such as a lunar crater)

Photoclinometry, or shape-from-shading, is the process by which a 2-dimensional image of a surface is transformed into a surface map that represents different levels of elevation. It uses the shadows and light direction as reference points. It is used mostly to depict the surface of sculptures, to give an idea of how it would look in 3-dimensions. The techniques depend on very specific conditions, especially light direction.