To determine how to set the Initial and Extra sample rates
         
         
            - Make sure the displacement mapped object is selected and its appears. 
            
- Display the tessellation triangles of the object. 
-  Preview the displacement results. 
            
- For each tessellation triangle, look at how much texture height variation is in the triangle, then (in the  section of the object’s ), adjust the Initial Sample Rate.
            
- For each tessellation triangle, notice how sharp the features are and how many curvy features there are. The sharper the features,
               the higher the Extra Sample Rate needs to be; adjust accordingly.