1. Go to the objects shader in the attribute panel or hypershader and click on the SG tab E.g. lambert2SG/blinn3SG.Click on the contour's drop down menu and enable contour rendering, here you can also choose what color you would like the contours to appear. Under width type .500.
2. Now go to render mental ray settings>features>contours and enable contour rendering again, Change the over-sample to 3 and filter type to Gaussian this will give your contours a smoother appearance.
3. Finally go to the draw by property difference drop down (under the contours tab) and select around all poly faces. Hit render!
You can also render objects with there materials and the contours by following the same process.