I am trying to make a 3D graphic using Illustrator. The graphic is supposed to consist of a cuboidal structure that is bent in some regions. I have been able to make the graphic by first making the 2D version using a rectangle (empty fill, 2 pt stroke, and then used the direct selection tool to use the rounded corner feature). After that, I used the extrude & bevel function to make it 3D.
However, I am seeing what are seemingly strange artifacts (see picture below). Would anyone here know what those are, why they appear and how I might get rid of them?
EDIT: I figured out that those lines appear only when I render the 3D graphic as a vector. When I rasterize it instead, I no longer see those lines. While this solves my problem for the moment, I'd appreciate any insight into how to avoid this problem while still rendering it as a vector graphic.