Smooths the normals of an object.
Inverts the normals of the object.
Just like you can disable the visibility for specific ray types, you can also change an object's sidedness depending on the ray type. By default, objects are double-sided for all rays. By unclicking any of these checkboxes, the object will become single-sided, which means that those parts of the object whose normal vector points away from the incoming ray direction will not be rendered.