Graphic option
contourDefault value: none
Option contour enables the user to select where to plot contour lines.
Possible values are:
none:
no contour lines are plotted.
base:
contour lines are projected on the xy plane.
surface:
contour lines are plotted on the surface.
both:
two contour lines are plotted: on the xy plane and on the surface.
map:
contour lines are projected on the xy plane, and the view point is
set just in the vertical.
Since this is a global graphics option, its position in the scene description does not matter.
Example: