Hi Shazbot - the regular circular fillet has a cross-sectional shape of an exact circular arc. But that also means that it may have different curvature than the surfaces on either side of it, and that's what causes the "rendered like separate pieces" type effect that you're describing. That's normal though for mechanical shapes to have that kind of appearance.

The G2 blend cross sectional shape will have curvature continuity between the surfaces and that makes it look more as if it's all one surface rather than having a distinct different shape of a circle in the fillet surface.

There is some more info on continuity here:

http://cadjunkie.com/1113/continuity-101
http://www.core77.com/blog/featured_items/a_periodic_table_of_form_the_secret_language_of_surface_and_meaning_in_product_design_by_gray_holland_12752.asp

- Michael

Hay Michael,
Great article, have you something more like this to read?

http://www.core77.com/blog/featured_items/a_periodic_table_of_form_the_secret_language_of_surface_and_meaning_in_product_design_by_gray_holland_12752.asp

Hi mir4ea, that's probably one of the best articles out there, I'm not really aware of any other article better than that, but if you want to search try using "Curvature continuity" or "G2 continuity" as the Google search terms. Many articles will deal more with the mathematical aspects though.

- Michael