featureEdges

Sharp edges of a triangulated surface, selected by the angle between adjacent faces.

Category: Mathematics > Computational Geometry

Syntax

E = featureEdges(TR, angle)

Description

For each edge shared by two triangles, the function measures the angle between the two face normals. An edge is kept when that angle is larger than the threshold. On a cube, the 12 edges at the corners are kept while the diagonals across the flat faces are dropped, since those faces are coplanar.

The result is typically drawn on top of a shaded surface to emphasise its creases.

Input arguments

TR

A triangulation of a 3-D surface (triangles).

angle

Threshold angle in radians, between 0 and pi.

Output arguments

E

Two-column matrix of vertex indices, one row per feature edge.

Example

Creases of a tetrahedron

P = [0 0 0; 1 0 0; 0 1 0; 0 0 1];
T = [1 3 2; 1 2 4; 1 4 3; 2 3 4];
tr = triangulation(T, P);
E = featureEdges(tr, pi/6)

E = 6×2

     1     2
     1     3
     1     4
     2     3
     2     4
     3     4

See also

faceNormal edges freeBoundary triangulation