surfnorm - Compute and display 3-D surface normals

Syntax

Description

surfnorm(Z) plots a surface of the matrix Z with surf and displays its surface normals as radiating vectors.

surfnorm(X,Y,Z) plots a surface and its surface normals from the vectors or matrices X, Y, and matrix Z

[Nx,Ny,Nz] = surfnorm(...) returns the components of the 3-D surface normals for the surface without plotting the surface or surface normals.

Tips

• surfnorm does not accept complex inputs.

• Reverse the direction of the normals by calling surfnorm with transposed arguments:

  surfnorm(X',Y',Z')
  

• The surface normals represent conditions at vertices and are not normalized. Normals for surface elements that face away from the viewer do not display.

• surfl uses surfnorm to compute surface normals when calculating the reflectance of a surface.

Input Arguments

Z	2-D matrix of real numbers representing a surface
X	Vector or matrix of real numbers that defines the x component of the surface
Y	Vector or matrix of real numbers that defines the y component of the surface

Output Arguments

[Nx,Ny,Nz]

x, y, and z components of the three-dimensional surface normals for the surface

Definitions

Surface Normal

An imaginary line perpendicular to a flat surface or perpendicular to the tangent plane at a point on a non-flat surface

Examples

Plot the normal vectors for a truncated cone.

[x,y,z] = cylinder(1:10);
surfnorm(x,y,z)
axis([-12 12 -12 12 -0.1 1])

Algorithms

After performing a bicubic fit of the data in the x, y, and z directions, diagonal vectors are computed and crossed to form the normal at each vertex.

See Also

isonormals | quiver3 | surf | surface | surfl

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