faceNormals - Class: TriRep
Unit normals to specified triangles
Syntax
FN = faceNormals(TR, TI)
Description
FN = faceNormals(TR, TI) returns the unit
normal vector to each of the specified triangles TI.
Note
This query is only applicable to triangular surface meshes. |
Inputs
| TR | Triangulation representation. |
| TI | Column vector of indices that index into the triangulation
matrix TR.Triangulation. |
Outputs
| FN | m-by-3 matrix. m = length(TI),
the number of triangles to be queried. Each row FN(i,:) represents
the unit normal vector to triangle TI(i). If
TI is not specified the unit normal information for the entire triangulation
is returned, where the normal associated with triangle i is the i'th
row of FN. |
Examples
Triangulate a sample of random points on the surface of a sphere
and use the TriRep to compute the normal to each
triangle:
numpts = 100;
thetha = rand(numpts,1)*2*pi;
phi = rand(numpts,1)*pi;
x = cos(thetha).*sin(phi);
y = sin(thetha).*sin(phi);
z = cos(phi);
dt = DelaunayTri(x,y,z);
[tri Xb] = freeBoundary(dt);
tr = TriRep(tri, Xb);
P = incenters(tr);
fn = faceNormals(tr);
trisurf(tri,Xb(:,1),Xb(:,2),Xb(:,3), ...
'FaceColor', 'cyan', 'faceAlpha', 0.8);
axis equal;
hold on;
Display the result using a quiver plot:
quiver3(P(:,1),P(:,2),P(:,3), ...
fn(:,1),fn(:,2),fn(:,3),0.5, 'color','r');
hold off;
See Also
 | ezsurfc | | factor |  |
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