3-D shaded surface with lighting.
SURFL(...) is the same as SURF (...) except that it draws the surface
with highlights from a light source.
SURFL(Z), SURFL(X,Y,Z), SURFL(Z,S), and SURFL(X,Y,Z,S) are all
legal. S, if specified, is the three vector S = [Sx,Sy,Sz]
that specifies the direction of the light source. S can also be
specified in spherical coordinates, S = [AZ,EL].
The shading is based on a combination of diffuse, specular and
ambient lighting models.
The default value for S is 45 degrees counterclockwise from
the current view direction. Use CLA , HOLD ON, VIEW (AZ,EL),
SURFL(...), HOLD OFF to plot the lighted surface with view
The relative contributions due to ambient light, diffuse
reflection, specular reflection, and the specular spread
coefficient can be set by using five arguments
SURFL(X,Y,Z,S,K) where K=[ka,kd,ks,spread].
Relies on the ordering of points in the X,Y, and Z matrices
to define the inside and outside of parametric surfaces.
Try SURFL(X',Y',Z') if you don't like the results of
this function. Due to the way surface normal vectors are
computed, SURFL requires matrices that are at least 3-by-3.
See also SURF1F43EU2.