R = SPECULAR(Nx,Ny,Nz,S,V) returns the reflectance of a surface with
normal vector components [Nx,Ny,Nz]. S and V specify the direction
to the light source and to the viewer, respectively. They can be
three vectors [x,y,z] or two vectors [Az, El] with azimuth and
The specular highlight is strongest when the normal vector is in the
direction of (S+V)/2 where S is the source direction, and V is the
The surface spread exponent can be specified by including a sixth
argument as in specular(Nx,Ny,Nz,S,V,spread).
See also DIFFUSE , SURFNORM , SURFL .