R code used to produce the graph shown below.

persp(x, y, z, theta=40, phi=45, col=blues[5]) 
persp(x, y, z, theta=40, phi=45, col=blues[5], shade=.3) 
persp(x, y, z, theta=40, phi=45, col=blues[5], shade=.3, 
      ticktype="detailed")