vertexNormal

Triangulation vertex normal

Syntax

V = vertexNormal(TR)

V = vertexNormal(TR,ID)

Description

V = vertexNormal(TR) returns the unit normal vectors to all vertices in a 3-D surface triangulation. V is a three-column matrix with each row containing the unit normal coordinates corresponding to the vertices in TR.Points.

V = vertexNormal(TR,ID) returns the unit normal vector to each vertex indexed by ID. A vertex ID is the row number corresponding to the vertices in the property TR.Points.

Examples

Surface of a Cube

Compute and plot the unit normal vectors to the vertices of a triangulation.

Create a 3-D triangulation representing the volume of a cube.

[X,Y,Z] = meshgrid(1:4);
x = X(:);
y = Y(:);
z = Z(:);
DT = delaunayTriangulation(x,y,z);

Triangulate the boundary of the cube.

[Tfb,Xfb] = freeBoundary(DT);
TR = triangulation(Tfb,Xfb);

Find the unit normal vectors to the triangle vertices.

V = vertexNormal(TR);

Plot the triangulated surface and the unit normal vectors.

trisurf(TR,'FaceColor',[0.8 0.8 1.0]);
axis equal
hold on
quiver3(Xfb(:,1),Xfb(:,2),Xfb(:,3), ...
     V(:,1),V(:,2),V(:,3),0.5,'Color','b');

Input Arguments

TR — Triangulation representation

scalar triangulation object

Triangulation representation for 3-D surface triangulations only, specified as a scalar triangulation or delaunayTriangulation object.

Data Types: triangulation | delaunayTriangulation

ID — Vertex IDs

scalar | column vector

Vertex IDs, specified as a scalar or a column vector whose elements correspond to a single vertex in the triangulation object. The ID of each vertex is the corresponding row number of the vertices in the Points property.

Data Types: double