The mesh below should represent an optical component in glass with smooth surfaces
When I’m rendering this in cycles (BL 2.74) using Glass BSDF surface and smooth shading I get an odd results with black areas, see image below.
The object to the left, included for comparison, is set to have Flat Shading and the Faces are thus clearly visible.
I have carefully checked that the normals are pointing from the interior glass to the exterior air.
Can anyone suggest what setting to change to make it look like a smooth piece of glass?