HEy guys, I've been building a circular turret that can be found on Hoth (from Star Wars) and am having problems with extrude face. When I render the turret without any extruded faces on the outside circumference of the cylinders, everything looks ok. However, if I want to add extra detail such as an inset grill on the outside circumference, and I do this by extruding faces, rezing the faces, and pushing or pulling the face. When I render this, however, you can see lines in the blinn texture where the face was extruded and pushed in or pulled out. How can I add extra detail to the turret without this problem occuring?

(If no one can understand what I'm saying, I'll post a picture)