featureEdges

(Not recommended) Sharp edges of surface triangulation

featureEdges(TriRep) is not recommended. Use featureEdges(triangulation) instead.

TriRep is not recommended. Use triangulation instead.

Syntax

FE = featureEdges(TR,filterangle)

Description

FE = featureEdges(TR,filterangle) returns an edge matrix FE. This method is typically used to extract the sharp edges in the surface mesh for the purpose of display. Edges that are shared by only one triangle and edges that are shared by more than two triangles are considered to be feature edges by default. For 2-D triangulations in MATLAB^®, the triangles are arranged in counter-clockwise order around the attached vertex.

Note

This query is only applicable to triangular surface meshes.

Examples

Feature Edges of Triangulation

Create a surface 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 = DelaunayTri(x,y);
tri = dt(:,:);

Elevate the 2-D mesh to create a surface.

z = [0 0 0 0 0 2 2 2 2 2 2 0 0 0 0 0 0 0 0 0 0 0]';
subplot(1,2,1)
trisurf(tri,x,y,z,'FaceColor','cyan')
axis equal

Compute the feature edges using a filter angle of pi/6.

tr = TriRep(tri,x,y,z);
fe = featureEdges(tr,pi/6)';

Highlight the feature edges in the triangulation with a second plot.

subplot(1,2,2)
trisurf(tr,'FaceColor','cyan','EdgeColor','none', ...
     'FaceAlpha',0.8)
axis equal
hold on
plot3(x(fe),y(fe),z(fe),'k','LineWidth',1.5)
hold off

Input Arguments

TR — Triangulation representation

TriRep or DelaunayTri object

Triangulation representation, specified as a TriRep or DelaunayTri object.

filterangle — Threshold angle

scalar

Threshold angle, specified as a scalar angle in radians. filterangle must be in the range $$(0,\pi )$$. featureEdges returns adjacent triangles with a dihedral angle that deviates from π by an angle greater than filterangle.

Output Arguments

FE — Feature edges

matrix

Feature edges, returned as a matrix. FE is of size m-by-2, where m is the number of computed feature edges in the mesh. The vertices of the edges index into the array of points representing the vertex coordinates, TR.X.

Extended Capabilities

Thread-Based Environment
Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

Version History

Introduced in R2009a