MR Rounded Corners black

[Peter M. Gruhn]

I made a thing. Unioned a bunch of boxes. Put a material on it with rounded corners. The edges between two visible faces look great. The outline edges show black in front of other things or parts of the same thing. I can see where this makes sense, but it looks awful. If I wanted a cel shader...

 

Anyway, I add some lights and backgrounds... keep workingon tarting up the scene and now that it's all pretty the black outlines are gone.

 

Now, I'm not going to complain that my rendering looks good, but it would have been nice if it started that way ;-).

 

Can anybody shed some light on the rounded edges effect and what might be happening here?

[novelh]

An image would help visualize the problem. Round corners claims to work best only on straight edges.