When using a coarse approximation of an object and imitating a smooth surface (by bending normals away from the geometry normal)
            you may find shadow artifacts. 
         
         To correct this try the following: 
         
            - Use fine approximation to fit the surface more precisely (see Approximation styles) 
            
- Disable Casts Shadows for the object to avoid self-shadowing (see Render Stats) 
            
- Use a separate shadow casting object to cast shadows onto other objects 
- Adjust the Ray Offset attribute on a per-object basis (see mental ray Ray Offset) 
            
- Use shadow maps with a Bias instead of raytraced shadows, if possible (see Shadow Map Attributes)