page_title: Ridge (differential geometry)
hierarchical_section_title: Ridge (differential geometry)
caption_attribution_description: English: I made this image, and I gift it to the public domain.
context_page_description: 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 set of ridge points form curves on the surface called ridges.
  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. There are two main cases: one has three ridge lines passing through the umbilic, and the other has one line passing through it.
  Ridge lines correspond to cuspidal edges on the focal surface.
context_section_description: 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 set of ridge points form curves on the surface called ridges.
  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. There are two main cases: one has three ridge lines passing through the umbilic, and the other has one line passing through it.
  Ridge lines correspond to cuspidal edges on the focal surface.
caption: A ridge
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