Triangulation unit normal vectors
F = faceNormal( returns the unit
normal vectors to all triangles in a 2-D triangulation. The
faceNormal function supports 2-D triangulations only.
F is a three-column matrix where each row contains the unit
normal coordinates corresponding to a triangle in
Unit Normals on a Surface
Compute and plot the unit normal vectors to the facets of a triangulation on a spherical surface.
Create a set of points on a spherical surface.
rng default; theta = rand([100,1])*2*pi; phi = rand([100,1])*pi; x = cos(theta).*sin(phi); y = sin(theta).*sin(phi); z = cos(phi);
Triangulate the sphere using the
DT = delaunayTriangulation(x,y,z);
Find the free boundary facets of the triangulation, and use them to create a 2-D triangulation on the surface.
[T,Xb] = freeBoundary(DT); TR = triangulation(T,Xb);
Compute the centers and face normals of each triangular facet in
P = incenter(TR); F = faceNormal(TR);
Plot the triangulation along with the centers and face normals.
trisurf(T,Xb(:,1),Xb(:,2),Xb(:,3), ... 'FaceColor','cyan','FaceAlpha',0.8); axis equal hold on quiver3(P(:,1),P(:,2),P(:,3), ... F(:,1),F(:,2),F(:,3),0.5,'color','r');
ID — Triangle identification
scalar | column vector
Triangle identification, specified as a scalar or a column vector whose
elements each correspond to a single triangle in the triangulation object.
The identification number of each triangle is the corresponding row number