Ridge (differential geometry)

In differential geometry, a smooth surface in three dimensions has a ridge point when a line of curvature has a local maximum or minimum of principal curvature.

The ridges of a given surface fall into two families, typically designated red and blue, depending on which of the two principal curvatures has an extremum.

At umbilical points the colour of a ridge will change from red to blue.

Ridge lines correspond to cuspidal edges on the focal surface.

This differential geometry-related article is a stub.