featureEdges

Sharp edges of surface triangulation

Syntax

F = featureEdges(TR,theta)

Description

F = featureEdges(TR,theta)returns thefeature edgesin a 2-D triangulation according to an angletheta. This function is typically used to extract sharp edges in a surface mesh plot.

Examples

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Surface Feature Edges

Open Live Script

Find and plot the feature edges of a surface.

Create a 2-D Delaunay triangulation.

x = [0 0 0 0 0 3 3 3 3 3 3 6 6 6 6 6 9 9 9 9 9 9]'; y = [0 2 4 6 8 0 1 3 5 7 8 0 2 4 6 8 0 1 3 5 7 8]'; DT = delaunayTriangulation(x,y); T = DT.ConnectivityList;

Add elevations to the triangulation to create a surface and plot the surface.

z = [0 0 0 0 0 2 2 2 2 2 2 0 0 0 0 0 0 0 0 0 0 0]'; trisurf(T,x,y,z,'FaceColor','cyan') axisequal

Figure contains an axes object. The axes object contains an object of type patch.

Create a new triangulation on the elevated surface, and compute and plot its feature edges using a filter angle of $\frac{π}{6}$ .

TR = triangulation(T,x,y,z); F = featureEdges(TR,pi/6)'; plot3(x(F),y(F),z(F),'k','LineWidth',1.5); axisequal

Figure contains an axes object. The axes object contains 24 objects of type line.

Input Arguments

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`TR`—Triangulation representation
scalar triangulation object

Triangulation representation for 2-D triangulations only, specified as a scalartriangulationordelaunayTriangulationobject.

Data Types:triangulation|delaunayTriangulation

`theta`—Filter angle
scalar

Filter angle in radians, specified as a scalar in the range [0,π].featureEdgesreturns adjacent triangles that have a dihedral angle that deviates from π by an angle greater thantheta.

Data Types:double

More About

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Feature Edge

A feature edge is a triangulation edge that has any of the following attributes:

The edge belongs to only one triangle.
The edge is shared by more than two triangles.
The edge is shared by a pair of triangles with angular deviation greater than the angletheta.

Fis a two-column matrix whose rows correspond to a feature edge. The first element of each row is the identification number of the starting edge vertex, and the second element is the identification number of the ending edge vertex. A vertex identification is the row number of the corresponding vertex in thePointsproperty.