mesh.face.normals: Compute the normals of the triangles of a mesh.

In freesurferformats: Read and Write 'FreeSurfer' Neuroimaging File Formats

Compute the normals of the triangles of a mesh.

Description

The normal of a triangle is the unit vector orthogonal to its plane, it is computed as the normalized cross product of two of its edges. The STL format stores one normal per triangle, and the value is computed from the geometry instead of being taken from the data, since a mesh in index representation does not store normals at all.

Usage

mesh.face.normals(vertex_coords, faces)

Arguments

vertex_coords	n x 3 matrix of doubles, the vertex coordinates.
faces	n x 3 matrix of integers, the vertex indices of the triangles.

Value

n x 3 matrix of doubles, the normalized normal of every face. Rows of degenerate triangles (whose 3 vertices lie on one line, which includes triangles with repeated vertices) are zero vectors, since such triangles have no plane and hence no normal.

freesurferformats documentation built on Sept. 25, 2026, 1:07 a.m.