[Goaliexam]

Sorry, I probably should have clarified a bit at the beginning:

Yes, I am sure it is a dome. I cropped out one of the corners, which showed it was actually the spec for an R2-D2 dome (I'm building an R2 for public demos to generate interest, as R2 is one of the few "robotic celebrities"). There is a club on Yahoo Groups that builds full size R2s based on the real thing and the real specs (measured and from insiders at LucasFilms).

As someone mentioned, the bottom 1.828 is actually a ring that the dome sits on top of, and which I didn't bother to remove from the drawing.

Attached is a screencap of the "seam" I was talking about. It doesn't appear when I render in Inventor Studio, but I'm still not convinced that it can't be avoided altogether.