Objects in my rendering are not smooth (faceted) and I can see shadows of polygons!

---This is issue has been fixed in Corona Renderer 1.6 - if you are experiencing it, please update to the newest version at https://corona-renderer.com/download ---

If the problem you are experiencing is visible on objects lit by strong, directional light or objects with exceptionally strong bump maps, then the only solution is to further subdivide the mesh (for example using TurboSmooth or Tesselate modifier). This limitation is typical for physically-based renderers not being able to cope with "fakes" such as shading normals. 

See: Known bugs and limitations