Normal Doctor
Find it: Click its button on the Looks palette: 
Use to:
-
Change the shading of an object's surface so that it appears more
faceted or more smooth. The more smooth an object is, the longer it
takes to render in a scene.
-
Flip polygon ordering so the object looks "inside-out."
-
Cull backface triangles so that polygons facing away from the viewer
are not rendered. This can make the object render more quickly in a
scene.
How it works:

Notes:
-
The values 0-180 refer to the crease
angle
in degrees. If the
angle between the normals for two adjacent polygons (the dihedral
angle) is less than the crease angle, then the polygon will be rendered
smoothly. If the dihedral angle is greater than the crease angle, then
the polygon will be rendered as faceted.
-
If you specify normals with a Normal node and normalPerVertex,
the creaseAngle is ignored. So if you select an object which
has specified normals, then open the Normal Doctor and set Render
Style, no change will take place.
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