Note:

FF = freeBoundary(TR)
[FF XF] = freeBoundary(TR)
FF = freeBoundary(TR)
returns a matrix FF
that
represents the free boundary facets of the triangulation. A facet
is on the free boundary if it is referenced by only one simplex (triangle/tetrahedron,
etc). FF
is of size m
byn
,
where m is the number of boundary facets and n is the number of vertices
per facet. The vertices of the facets index into the array of points
representing the vertex coordinates TR.X
. The array FF
could
be empty as in the case of a triangular mesh representing the surface
of a sphere.
[FF XF] = freeBoundary(TR)
returns a matrix
of free boundary facets
TR  Triangulation representation. 
FF  FF that has vertices defined in terms of
a compact array of coordinates XF . 
XF  XF is of size m byndim where m is
the number of free facets, and ndim is the dimension
of the space where the triangulation resides 
A simplex is a triangle/tetrahedron or higherdimensional equivalent. A facet is an edge of a triangle or a face of a tetrahedron.
Use TriRep
to compute the boundary triangulation
of an imported triangulation.
Load a 3D triangulation:
load tetmesh; trep = TriRep(tet, X);
Compute the boundary triangulation:
[tri xf] = freeBoundary(trep);
Plot the boundary triangulation:
trisurf(tri, xf(:,1),xf(:,2),xf(:,3), ... 'FaceColor','cyan', 'FaceAlpha', 0.8);
Perform a direct query of a 2D triangulation created with DelaunayTri
.
Plot the mesh:
x = rand(20,1); y = rand(20,1); dt = DelaunayTri(x,y); fe = freeBoundary(dt)'; triplot(dt); hold on;
Display the free boundary edges in red:
plot(x(fe), y(fe), 'r', 'LineWidth',2) ; hold off;
In this instance the free edges correspond to the convex hull
of (x, y)
.
convexHull
 delaunayTriangulation
 faceNormal
 featureEdges
 triangulation