Gumroad - Improved Face Weighted Normals Script for 3ds Maxhttp://www.scriptspot.com/3ds-max/plugins/keyhydra-for-3dsmaxWeighted Vertex Normals or Face Weighted...
This script does this for you with just one click.
Unlike others FWN Scripts, this one considers coplanar faces like they were a unique big face
You can disable this feature to get an standard FWN result, or increase threshold for not completely flat surfaces